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					GLOSSARY
   Refractive Surgery


              August 2009


         Alcon Laboratories, Inc.
           6201 South Freeway
     Fort Worth, TX 76134-2099, USA
          Tel. (+1) 817.293.0450
              www.alcon.com


             WaveLight AG
Am Wolfsmantel 5, 91058 Erlangen, Germany
          Tel. +49/9131/6186-0
           www.wavelight.com
20/20 ................................................................................................................................. 12
A SCAN ............................................................................................................................ 12
AAO .................................................................................................................................. 12
ABBOTT MEDICAL OPTICS ........................................................................................... 12
ABES ................................................................................................................................ 12
ABLATION ........................................................................................................................ 12
ABLATION ZONE ............................................................................................................. 12
ABMD................................................................................................................................ 12
ABO .................................................................................................................................. 12
ACCOMMODATION......................................................................................................... 13
ACCOMMODATIVE INSUFFICIENCY ............................................................................ 13
ACES ................................................................................................................................ 13
ACUITY............................................................................................................................. 13
ADNEXA ........................................................................................................................... 13
AGAINST-THE-RULE ASTIGMATISM ............................................................................ 13
AGE-RELATED MACULAR DEGENERATION ............................................................... 13
AK ..................................................................................................................................... 13
ALCON ............................................................................................................................. 13
ALGORITHM .................................................................................................................... 14
ALK ................................................................................................................................... 14
ALLEGRETTO .................................................................................................................. 14
ALLERGAN....................................................................................................................... 14
AMBLYOPIA ..................................................................................................................... 14
AMD .................................................................................................................................. 14
AMERICAN ACADEMY OF OPHTHALMOLOGY ........................................................... 14
AMERICAN ACADEMY OF OPTOMETRY ..................................................................... 14
AMERICAN BOARD OF EYE SURGERY ....................................................................... 14
AMERICAN BOARD OF OPHTHALMOLOGY ................................................................ 15
AMERICAN COLLEGE OF EYE SURGEONS ................................................................ 15
AMERICAN COLLEGE OF SURGEONS ........................................................................ 15
AMERICAN OPTOMETRIC ASSOCIATION ................................................................... 15
AMERICAN SOCIETY OF CATARACT AND REFRACTIVE SURGERY....................... 15
AMETROPIA..................................................................................................................... 15
AMO .................................................................................................................................. 15
AMSLER GRID ................................................................................................................. 15
ANISEIKONIA................................................................................................................... 15
ANISOMETROPIA............................................................................................................ 16
ANISOMETROPIA............................................................................................................ 16
ANOPHTHALMIA ............................................................................................................. 16
ANOPIA ............................................................................................................................ 16
ANTERIOR ....................................................................................................................... 16
ANTERIOR BASEMENT MEMBRANE DYSTROPHY .................................................... 16
ANTERIOR CHAMBER .................................................................................................... 16
ANTERIOR OCULAR SEGMENT.................................................................................... 16
ANTIMETROPIA............................................................................................................... 16
ANTIOXIDANTS ............................................................................................................... 16
AOA .................................................................................................................................. 16
APHAKIA .......................................................................................................................... 17
APHAKIC SPECTACLES................................................................................................. 17
AQUEOUS FLUID ............................................................................................................ 17



                                                                                                                                         2
AQUEOUS HUMOR ......................................................................................................... 17
ARGON LASER................................................................................................................ 17
ARMD ............................................................................................................................... 17
ASCRS ............................................................................................................................. 17
ASTIGMATIC KERATOTOMY ......................................................................................... 17
ASTIGMATISM ................................................................................................................. 17
ATOPY.............................................................................................................................. 18
ANTERIOR CHAMBER .................................................................................................... 18
AUTOMATED LAMELLAR KERATOPLASTY................................................................. 18
AUTOMATED PERIMETER............................................................................................. 18
B SCAN ............................................................................................................................ 18
BARRAQUER CYRO-LATHE .......................................................................................... 18
BASEMENT MEMBRANE................................................................................................ 18
BAUSCH & LOMB ............................................................................................................ 19
BCVA ................................................................................................................................ 19
BEST CORRECTED VISUAL ACUITY ............................................................................ 19
BIFOCALS ........................................................................................................................ 19
BINOCULAR..................................................................................................................... 19
BINOCULAR VISION ....................................................................................................... 19
BLACK BOX LASER ........................................................................................................ 19
BLEPHARITIS .................................................................................................................. 19
BLIND SPOT .................................................................................................................... 19
BOARD CERTIFIED......................................................................................................... 19
BOWMAN'S LAYER ......................................................................................................... 20
BROADBEAM................................................................................................................... 20
BUTTONHOLE FLAP ....................................................................................................... 20
C3-R.................................................................................................................................. 20
C-CAP............................................................................................................................... 20
CALHOUN VISION........................................................................................................... 20
CANTHUS ........................................................................................................................ 20
CATARACT ...................................................................................................................... 21
CENTRAL ISLAND........................................................................................................... 21
CENTRAL RETINAL ARTERY......................................................................................... 21
CENTRAL RETINAL VEIN ............................................................................................... 21
CENTRAL VISION............................................................................................................ 21
CHOROID......................................................................................................................... 21
CILIARY MUSCLES ......................................................................................................... 21
CILIARY PROCESSES .................................................................................................... 21
CK ..................................................................................................................................... 21
CLAPIKS........................................................................................................................... 21
CLE ................................................................................................................................... 22
CLEAR LENS EXCHANGE.............................................................................................. 22
CLEAR LENS REPLACEMENT ....................................................................................... 22
CLINICAL TRIAL .............................................................................................................. 22
CLR................................................................................................................................... 22
COHERENT MEDICAL GROUP...................................................................................... 22
COLLARETTE .................................................................................................................. 22
COLOR VISION................................................................................................................ 22
COMANAGEMENT .......................................................................................................... 22
COMPLEX WAVEFRONT RETREATMENT ................................................................... 22



                                                                                                                                         3
CONCAVE LENS ............................................................................................................. 23
CONDUCTIVE KERATOPLASTY.................................................................................... 23
CONE CELLS................................................................................................................... 23
CONFORMER .................................................................................................................. 23
CONJUNCTIVA ................................................................................................................ 23
CONJUNCTIVITIS ............................................................................................................ 23
CONTACT LENS .............................................................................................................. 23
CONTACT LENS ASSISTED PHARMACOLOGICALLY INDUCED KERATO
STEEPENING .................................................................................................................. 23
CONTACT LENS DISINFECTANT .................................................................................. 23
CONTACT LENS, DAILY WEAR ..................................................................................... 24
CONTACT LENS, DISPOSABLE..................................................................................... 24
CONTACT LENS, EXTENDED WEAR ............................................................................ 24
CONTACT LENS, THERAPEUTIC .................................................................................. 24
CONTACT LENS, TORIC ................................................................................................ 24
CONTRAST SENSITIVITY............................................................................................... 24
CONVERGENCE/DIVERGENCE .................................................................................... 24
CONVEX LENS ................................................................................................................ 24
CORNEA .......................................................................................................................... 25
CORNEAL ABRASION .................................................................................................... 25
CORNEAL COLLAGEN CROSSLINKING WITH RIBOFLAVIN ..................................... 25
CORNEAL ENDOTHELIAL CELL DYSTROPHY ............................................................ 25
CORNEAL HAZE.............................................................................................................. 25
CORNEAL REFRACTIVE THERAPY .............................................................................. 25
CORNEAL REMODELING............................................................................................... 25
CORNEAL TOPOGRAPHICAL MAP ............................................................................... 25
CORNEAL TOPOGRAPHY ............................................................................................. 26
COUNCIL FOR REFRACTIVE SURGERY QUALITY ASSURANCE ............................. 26
CREDENTIALS ................................................................................................................ 26
CRSQA ............................................................................................................................. 26
CRT................................................................................................................................... 26
CRYSTALENS.................................................................................................................. 26
CRYSTALLINE LENS ...................................................................................................... 26
CUSTOM CONTOURED ABLATION PATTERN ............................................................ 26
CUSTOM CORNEA.......................................................................................................... 27
CUSTOMVUE................................................................................................................... 27
CWR ................................................................................................................................. 27
CYCLOPEGIC REFRACTION ......................................................................................... 27
CYCLOROTATION........................................................................................................... 27
CYCLOTORSION............................................................................................................. 27
DAY BLINDNESS ............................................................................................................. 28
DECENTRATION ............................................................................................................. 28
DEEP LAMELLAR ENDOTHELIAL KERATOPLASTY ................................................... 28
DESCEMET'S LAYER...................................................................................................... 28
DEPTH PERCEPTION..................................................................................................... 28
DIABETES MELLITUS ..................................................................................................... 28
DIABETES TYPE I ........................................................................................................... 28
DIABETES TYPE II .......................................................................................................... 29
DIABETIC RETINOPATHY .............................................................................................. 29
DIFFUSE LAMELLAR KERATITIS .................................................................................. 29



                                                                                                                                       4
DILATION ......................................................................................................................... 29
DIOPTER.......................................................................................................................... 29
DIPLOPIA ......................................................................................................................... 29
DISPENSING OPTICIAN ................................................................................................. 29
DLK ................................................................................................................................... 29
DO..................................................................................................................................... 29
DOCTORATE OF OSTEOPATHY ................................................................................... 30
DOMINANT EYE .............................................................................................................. 30
DOUBLE IMAGE .............................................................................................................. 30
DRUSEN........................................................................................................................... 30
DRY EYE .......................................................................................................................... 30
DYSTROPHY ................................................................................................................... 30
EBMD................................................................................................................................ 31
ECCE................................................................................................................................ 31
ECTASIA .......................................................................................................................... 31
EDEMA ............................................................................................................................. 31
EMMETROPIA ................................................................................................................. 31
ENDO................................................................................................................................ 31
ENDOPHTHALMITIS ....................................................................................................... 31
ENDOTHELIUM ............................................................................................................... 31
ENHANCEMENT .............................................................................................................. 31
ENUCLEATION ................................................................................................................ 32
EPHIPHORA..................................................................................................................... 32
EPIKERATOME................................................................................................................ 32
EPI-LASIK......................................................................................................................... 32
EPITHELIUM .................................................................................................................... 32
EPITHELIUM BASEMENT MEMBRANE DYSTROPHY ................................................. 32
EPITHELIAL INGROWTH................................................................................................ 32
ESOPHORIA .................................................................................................................... 32
ESOTROPIA..................................................................................................................... 32
EXCIMER LASER ............................................................................................................ 33
EXOPHORIA .................................................................................................................... 33
EXOTROPIA..................................................................................................................... 33
EXTERNAL OCULAR MUSCLES.................................................................................... 33
EXTRACAPSULAR CATARACT EXTRACTION............................................................. 33
FACS ................................................................................................................................ 33
FARSIGHTEDNESS ........................................................................................................ 33
FDA................................................................................................................................... 33
FLAP & ZAP ..................................................................................................................... 34
FEMTOSECOND LASER................................................................................................. 34
FLUORESCEIN ANGIOGRAPHY.................................................................................... 34
FLUORESCEIN STAINING.............................................................................................. 34
FLYING SPOT .................................................................................................................. 34
FOCUSING POWER OF THE EYE ................................................................................. 34
FOOD AND DRUG ADMINISTRATION........................................................................... 34
FOVEA.............................................................................................................................. 34
FREERADICAL ................................................................................................................ 35
FUCH'S DYSTROPHY ..................................................................................................... 35
FUNCTIONAL VISUAL DISABILITY ................................................................................ 35
FUNDUS ........................................................................................................................... 35



                                                                                                                                        5
GAUSSIAN ....................................................................................................................... 35
GHOSTING....................................................................................................................... 35
GLAUCOMA ..................................................................................................................... 35
GONIOSCOPY................................................................................................................. 35
GRAY BOX LASER .......................................................................................................... 36
HALOS.............................................................................................................................. 36
HAPTICS .......................................................................................................................... 36
HAZE ................................................................................................................................ 36
HEALTH MAINTENANCE ORGANIZATION ................................................................... 36
HEMERALOPIA................................................................................................................ 36
HIGHER ORDER ABERRATION..................................................................................... 37
HMO.................................................................................................................................. 37
HOA .................................................................................................................................. 37
HUMANITARIAN DEVICE EXEMPTION ......................................................................... 37
HYPEROPIA..................................................................................................................... 37
HYPOBARIC..................................................................................................................... 37
HYPOXIA .......................................................................................................................... 37
ICL .................................................................................................................................... 38
ICRS ................................................................................................................................. 38
IMPLANTABLE COLLAMER LENS ................................................................................. 38
INTACS............................................................................................................................. 38
INTRAOCULAR ................................................................................................................ 38
INTRAOCULAR LENS ..................................................................................................... 38
INTRAOCULAR PRESSURE........................................................................................... 38
IRIS ................................................................................................................................... 38
INTRAOPERATIVE .......................................................................................................... 39
INTRASTROMAL CORNEAL RING SEGMENTS ........................................................... 39
IOL .................................................................................................................................... 39
IOP .................................................................................................................................... 39
ISCHEMIA ........................................................................................................................ 39
JCAHO.............................................................................................................................. 39
JOINT COMMISSION ON ACCREDITATION OF HEALTHCARE ORGANIZATIONS .. 39
KELOID............................................................................................................................. 40
KERATECTOMY .............................................................................................................. 40
KERATITIS ....................................................................................................................... 40
KERATO ........................................................................................................................... 40
KERATOCONJUNCTIVITIS............................................................................................. 40
KERATOCONUS .............................................................................................................. 40
KERATOMETRY .............................................................................................................. 40
KERATOMILEUSIS .......................................................................................................... 40
KERATOTOMY ................................................................................................................ 40
KERAVISION.................................................................................................................... 40
LACRIMAL GLAND .......................................................................................................... 41
LAGOPHTHALMOS ......................................................................................................... 41
LAL.................................................................................................................................... 41
LASEK .............................................................................................................................. 41
LASER .............................................................................................................................. 41
LASER ASSISTED IN-SITU KERATOMILEUSIS ........................................................... 41
LASER ASSISTED EPITHELIUM KERATOMILEUSIS ................................................... 41
LASERSIGHT ................................................................................................................... 42



                                                                                                                                         6
LASER THERMAL KERATOPLASTY ............................................................................. 42
LASIK................................................................................................................................ 42
LATTICE DEGENERATION............................................................................................. 42
LEGAL BLINDNESS ........................................................................................................ 42
LENS................................................................................................................................. 42
LENTICULAR ASTIGMATISM ......................................................................................... 42
LIGHT ADJUSTABLE LENS ............................................................................................ 42
LIMBUS ............................................................................................................................ 43
LTK ................................................................................................................................... 43
LOW VISION .................................................................................................................... 43
MACRO STRIAE .............................................................................................................. 43
MACULA ........................................................................................................................... 43
MACULAR EDEMA .......................................................................................................... 43
MANIFEST REFRACTION............................................................................................... 43
MASKS ............................................................................................................................. 43
MD .................................................................................................................................... 44
MEDIAL ............................................................................................................................ 44
MEDICAL DOCTORATE.................................................................................................. 44
MEIBOMIAN GLANDS ..................................................................................................... 44
MEIBOMIAN GLAND DYSFUNCTION ............................................................................ 44
MEIBOMITIS..................................................................................................................... 44
MESOPIC PUPIL SIZE .................................................................................................... 44
MICRO STRIAE................................................................................................................ 44
MICRON ........................................................................................................................... 44
MICROKERATOME ......................................................................................................... 45
MICROPHTHALMIA ......................................................................................................... 45
MILLIMICRON .................................................................................................................. 45
MIOSIS ............................................................................................................................. 45
MONOCULAR .................................................................................................................. 45
MONOVISION .................................................................................................................. 45
MUNNERLYN FORMULA ................................................................................................ 45
MYDRIASIS ...................................................................................................................... 45
MYOPIA ............................................................................................................................ 45
NANOMETER................................................................................................................... 46
NASAL .............................................................................................................................. 46
NATIONAL COMMITTEE FOR QUALITY ASSURANCE ............................................... 46
NATIONAL EYE INSTITUTE ........................................................................................... 46
NCQA................................................................................................................................ 46
NEAR POINT OF ACCOMMODATION ........................................................................... 46
NEAR POINT OF CONVERGENCE ................................................................................ 46
NEARSIGHTEDNESS...................................................................................................... 46
NEARVISION CK ............................................................................................................. 46
NEI .................................................................................................................................... 46
NEOVASCULARIZATION ................................................................................................ 47
NUCLEAR SCLEROSIS................................................................................................... 47
NIDEK ............................................................................................................................... 47
NIGHT BLINDNESS ......................................................................................................... 47
NYCTALOPIA ................................................................................................................... 47
NYSTAGMUS ................................................................................................................... 47
OCULAR HYPERTENSION ............................................................................................. 48



                                                                                                                                         7
OCULAR ROSACEA........................................................................................................ 48
OFF LABEL USE .............................................................................................................. 48
OPHTHALMIC .................................................................................................................. 48
OPHTHALMIC IMAGING SYSTEMS............................................................................... 48
OPHTHALMOLOGIST ..................................................................................................... 48
OPHTHALMOSCOPY ...................................................................................................... 48
OPTIC CUP ...................................................................................................................... 49
OPTIC DISK ..................................................................................................................... 49
OPTIC NERVE ................................................................................................................. 49
OPTICAL ZONE ............................................................................................................... 49
OPTICIAN ......................................................................................................................... 49
OPTOMETRIST................................................................................................................ 49
ORTHOKERATOLOGY.................................................................................................... 49
OVERCORRECTION ....................................................................................................... 49
PACHYMETRY................................................................................................................. 50
PAPILLEDEMA................................................................................................................. 50
PELLUCID MARGINAL DEGENERATION...................................................................... 50
PENETRATING KERATOPLASTY .................................................................................. 50
PERIPHERAL VISION ..................................................................................................... 50
PERIOPERATIVE............................................................................................................. 50
PERK STUDY................................................................................................................... 50
PHACOEMULSIFICATION .............................................................................................. 51
PHAKIC ............................................................................................................................ 51
PHAKIC INTRAOCULAR LENS....................................................................................... 51
P-IOL................................................................................................................................. 51
PHI-MOTION ANGIOGRAPHY ........................................................................................ 51
PHOROPTER................................................................................................................... 51
PHOTOTHERAPEUTIC KERATECTOMY ...................................................................... 51
PHOTOABLATION ........................................................................................................... 52
PHOTOCOAGULATION .................................................................................................. 52
PHOTOPHOBIA ............................................................................................................... 52
PHOTOREFRACTIVE KERATECTOMY ......................................................................... 52
PHOTOVAPORIZATION .................................................................................................. 52
PHTHISIS BULBI.............................................................................................................. 52
PINGUECULA .................................................................................................................. 52
PINHOLE GLASSES ........................................................................................................ 52
PK ..................................................................................................................................... 52
PLANO.............................................................................................................................. 53
POINT SPREAD FUNCTION ........................................................................................... 53
POLYNOMIAL .................................................................................................................. 53
POLYOPIA........................................................................................................................ 53
POSTERIOR..................................................................................................................... 53
POSTERIOR CAPSULAR OPACIFICATION .................................................................. 53
POSTERIOR CHAMBER ................................................................................................. 53
POSTERIOR OPTICAL SEGMENT................................................................................. 53
POSTERIOR VITREOUS DETACHMENT ...................................................................... 54
PPO .................................................................................................................................. 54
PREFERRED PROVIDER ORGANIZATION .................................................................. 54
PRELEX............................................................................................................................ 54
PREOPERATIVE.............................................................................................................. 54



                                                                                                                                         8
PRESBYOPIA .................................................................................................................. 54
PRESBYOPIC LENS EXCHANGE .................................................................................. 54
PRESCRIPTION TERMS................................................................................................. 55
PRESVIEW ....................................................................................................................... 55
PRISM............................................................................................................................... 55
PRK................................................................................................................................... 55
PSF ................................................................................................................................... 55
PSEUDOPHAKIC ............................................................................................................. 56
PTK ................................................................................................................................... 56
PTYGERIA........................................................................................................................ 56
PUNCTAL OCCLUSION .................................................................................................. 56
PUNCTAL PLUGS............................................................................................................ 56
PUNCTUM ........................................................................................................................ 56
PUPIL................................................................................................................................ 56
PUPILLARY RESPONSE................................................................................................. 56
READERS ........................................................................................................................ 57
REALLY SIMPLE SYNDICATION ................................................................................... 57
READING GLASSES ....................................................................................................... 57
RADIAL ............................................................................................................................. 57
RADIAL KERATOTOMY .................................................................................................. 57
REFRACTEC.................................................................................................................... 57
REFRACTION .................................................................................................................. 57
REFRACTIVE ERROR..................................................................................................... 57
REFRACTIVE LENS EXCHANGE................................................................................... 58
REFRACTIVE SURGERY................................................................................................ 58
REGRESSION.................................................................................................................. 58
RESTASIS ........................................................................................................................ 58
ReSTOR ........................................................................................................................... 58
RETINA............................................................................................................................. 58
RETINAL AXONS ............................................................................................................. 58
RETINAL DETACHMENT ................................................................................................ 58
RETINAL PIGMENT EPITHELIUM .................................................................................. 59
RETINITIS PIGMENTOSA ............................................................................................... 59
RETREATMENT............................................................................................................... 59
ReZOOM .......................................................................................................................... 59
RGP .................................................................................................................................. 59
RIGID GAS PERMEABLE CONTACT LENS .................................................................. 59
RK ..................................................................................................................................... 59
RLE ................................................................................................................................... 59
RMS .................................................................................................................................. 59
RSS................................................................................................................................... 59
RODS, ROD CELLS......................................................................................................... 60
ROOT MEAN SQUARE ................................................................................................... 60
ROSACEA ........................................................................................................................ 60
SALINE SOLUTION ......................................................................................................... 60
SANDS OF SAHARA ....................................................................................................... 60
SCHLEMM'S CANAL ....................................................................................................... 60
SCLERA ........................................................................................................................... 60
SCLERAL SHELL ............................................................................................................. 60
SCOTOPIC PUPIL SIZE .................................................................................................. 61



                                                                                                                                         9
SCOTOMA........................................................................................................................ 61
SECONDARY IMPLANT .................................................................................................. 61
SEE................................................................................................................................... 61
SHIRMER TEST ............................................................................................................... 61
SIDE VISION .................................................................................................................... 61
SLIT LAMP ....................................................................................................................... 61
SNELLEN VISUAL ACUITY TEST .................................................................................. 61
SOCIETY FOR EXCELLENCE IN EYECARE ................................................................. 61
SOS .................................................................................................................................. 62
SPHERE ........................................................................................................................... 62
SRP................................................................................................................................... 62
STRABISMUS .................................................................................................................. 62
STARBURSTS ................................................................................................................. 62
STEREOPSIS................................................................................................................... 62
STEROID.......................................................................................................................... 62
STILES-CRAWFORD EFFECT ....................................................................................... 62
STRIAE ............................................................................................................................. 63
STROMA .......................................................................................................................... 63
SEBORRHEIC DERMATITIS........................................................................................... 63
SURGICAL REVERSAL OF PRESBYOPIA .................................................................... 63
SULCUS ........................................................................................................................... 63
SUMMIT............................................................................................................................ 63
SUNRISE TECHNOLOGIES............................................................................................ 63
SUPERIOR ....................................................................................................................... 63
SUPPRESSION................................................................................................................ 63
SURFACE ABLATION ..................................................................................................... 63
TBUT................................................................................................................................. 64
TEAR BREAK UP TEST .................................................................................................. 64
TEMPORAL ...................................................................................................................... 64
TONOMETRY................................................................................................................... 64
TOPCON .......................................................................................................................... 64
TOPOGRAPHY-GUIDED REFRACTIVE SURGERY ..................................................... 64
TOPOGRAPHY ................................................................................................................ 64
TORIC............................................................................................................................... 64
TRABECULAR MESHWORK .......................................................................................... 64
TRANSITION ZONE......................................................................................................... 65
TRIFOCALS...................................................................................................................... 65
UCVA ................................................................................................................................ 65
ULTRASOUND ................................................................................................................. 65
ULTRAVIOLET RADIATION ............................................................................................ 65
um ..................................................................................................................................... 65
UNCORRECTED VISUAL ACUITY ................................................................................. 65
UNDERCORRECTION .................................................................................................... 66
UVEA, UVEAL TRACT ..................................................................................................... 66
VARIABLE SPOT ............................................................................................................. 66
VISIAN ICL ....................................................................................................................... 66
VISION THERAPY ........................................................................................................... 66
VISUAL ACUITY............................................................................................................... 66
VISUAL AXIS.................................................................................................................... 66
VISUAL FIELD.................................................................................................................. 67



                                                                                                                                       10
VITREORETINAL ............................................................................................................. 67
VITREOUS HUMOR ........................................................................................................ 67
WAVE LENGTH ............................................................................................................... 68
WAVEFRONT................................................................................................................... 68
WAVELIGHT..................................................................................................................... 68
WELCH ALLYN ................................................................................................................ 68
WITH-THE-RULE ASTIGMATISM ................................................................................... 68
YAG LASER ..................................................................................................................... 69
ZEISS................................................................................................................................ 69
ZERNIKE .......................................................................................................................... 69
ZERNIKE POLYNOMIAL ................................................................................................. 69
ZYOPTIX .......................................................................................................................... 69
ZONULES ......................................................................................................................... 70




                                                                                                                                    11
A
20/20
Fraction commonly used to indicate normal vision. A bottom number larger than twenty
indicates diminished vision. For example, a person with 20/ 400 vision would see a line of text
that is twenty feet away with the same readability that a person with "normal" vision would
see that line of text from 400 feet away.


A SCAN
Ultrasonic procedure to measure specific areas within the eye.


AAO
See American Academy of Ophthalmology or the American Academy of Optometry.


ABBOTT MEDICAL OPTICS
Ophthalmic equipment company. Click here to go to website.


ABES
See American Board of Eye Surgery.


ABLATION
Removal. In the case of the excimer laser, the frequency of energy causes the molecules of
the cornea to loose the "glue" that holds them together. They simply fall away from each
other and the remaining cornea.


ABLATION ZONE
The area of the cornea including the fully corrected optical ablation zone and the transition
zone.


ABMD
See Anterior Basement Membrane Dystrophy.


ABO
See American Board of Ophthalmology.




                                                                                                12
ACCOMMODATION
The ability of the eye to change focus from distant objects to objects closer than optical
infinity, approximately 20 feet (6 meters). Like when driving and you switch from looking
down the road to reading the speedometer. Accommodation is achieved when the lens
shape is changed by small muscles around the lens pushing and pulling. Loss of
accommodation is called presbyopia.


ACCOMMODATIVE INSUFFICIENCY
Loss of or less than expected amount of accommodation.


ACES
See American College of Eye Surgeons.


ACUITY
Clearness, as in visual acuity. The most common measure of visual acuity is the Snellen
acuity chart. Normal acuity being 20/20 (6/6 metric version).


ADNEXA
The accessory structures of the eye including the eyelids, lacrimal apparatus, etc.


AGAINST-THE-RULE ASTIGMATISM
"With the rule" astigmatism has an axis of about 180 degrees (when Rx is written in minus
cylinder form). "Against the rule" astigmatism has the axis at about 90 degrees.
Both forms are common. Nevertheless, when looking at population norms, "with the rule" is
more common in young adults while "against the rule" is more common in older adults.


AGE-RELATED MACULAR DEGENERATION
Destruction and loss of the photoreceptors in the macula region of the retina resulting in
decreased central vision and, in advanced cases, blindness.


AK
See Astigmatic Keratotomy.


ALCON
Medical device manufacturer. Click here to go to website.




                                                                                             13
ALGORITHM
A precise mathematical rule or set of rules to find a solution to a problem. In refractive
surgery, algorithm often refers to the mathematical calculations of the excimer laser used to
create an ablation pattern to reshape the cornea for the purpose of reducing the need for
corrective lenses, such as in LASIK, PRK, LASEK, or Epi-LASIK.


ALK
See Automated Lamellar Keratoplasty.


ALLEGRETTO
Medical device manufacturer. Click here to go to website.


ALLERGAN
Ophthalmic equipment and drug company. Click here to go to website.


AMBLYOPIA
Often called "lazy eye" it is an unilateral (occasionally bilateral) condition in which, in the
absence of any obvious structural anomalies or ocular disease, the best corrected vision is
less than 20/20 (6/6). Amblyopia often occurs in an eye that did not have adequate use
during early childhood.

Most often amblyopia results from either a misalignment of a child's eyes, such as crossed
eyes, or a difference in image quality between the two eyes (one eye focusing better than the
other.) In both cases, one eye becomes stronger, suppressing the image of the other eye. If
this condition persists, the weaker eye may becomes useless. With early diagnosis and
treatment, the sight in the "lazy eye" can be restored.


AMD
See Age-Related Macular Degeneration.


AMERICAN ACADEMY OF OPHTHALMOLOGY
Ophthalmologist membership organization. Click here to go to website.


AMERICAN ACADEMY OF OPTOMETRY
Optometrist membership organization. Click here to go to website.


AMERICAN BOARD OF EYE SURGERY
Ophthalmologist certification organization. Affiliated with the American College of Eye
Surgeons. Click here to go to website.




                                                                                                  14
AMERICAN BOARD OF OPHTHALMOLOGY
A medical specialty board that administers a 1-1/2 year long education and examination
process for ophthalmologists. After an ophthalmologist has passed the examination, (s)he is
"Board Certified". Click here to go to website.


AMERICAN COLLEGE OF EYE SURGEONS
Ophthalmologist membership organization. Affiliated with the American Board of Eye
Surgeons. Click here to go to website.


AMERICAN COLLEGE OF SURGEONS
Medical membership organization. Members are called Fellows. Physicians who are
members often use the acronym FACS after their name. Click here to go to website.


AMERICAN OPTOMETRIC ASSOCIATION
Optometric membership organization. Click here to go to website.


AMERICAN SOCIETY OF CATARACT AND REFRACTIVE SURGERY
Ophthalmologist membership organization. Click here to go to website.


AMETROPIA
Any imperfection in refractive state of the eye. Examples would be hyperopia (farsighted,
longsighted vision), myopia (nearsighted, shortsighted vision), or astigmatism (irregular
cornea).


AMO
See Abbott Medical Optics.


AMSLER GRID
A hand held chart featuring horizontal and vertical lines, usually white on black background,
used to test for central visual field defects.


ANISEIKONIA
Aniseikonia is a binocular condition in which left and right images differ in size or shape.
There are two types of aniseikonia – static and dynamic aniseikonia. The first type is the
classical aniseikonia, denoting a perceived image size difference with a fixed gaze direction.
Classic aniseikonia can occur naturally or be induced by refractive surgery.
The second type of aniseikonia is also called induced anisophoria and denotes a perceived
image size difference due to unequal prism effects when looking through different parts of
the two (anisometropic) spectacle lenses.




                                                                                             15
ANISOMETROPIA
The condition in which the two eyes have an unequal refractive power. One eye may be
myopic (nearsighted, shortsighted) and the other hyperopic (farsighted, longsighted).


ANISOMETROPIA
The absence of refractive error symmetry between both eyes. If one person's eye has a
refractive error that is more than one diopter greater than the other, it is called anisometropia.


ANOPHTHALMIA
Congenital absence of eyes.


ANOPIA
Absence of eyes.


ANTERIOR
Front or forward portion.


ANTERIOR BASEMENT MEMBRANE DYSTROPHY
Also called Epithelium Basement Membrane Dystrophy, is a disease that disrupts the ability
of the epithelium to attach to the lower layers of the cornea. The epithelium will often grow
unevenly or will detach from the cornea.


ANTERIOR CHAMBER
The space in front of the iris and behind the cornea.


ANTERIOR OCULAR SEGMENT
The part of the eye anterior to the crystalline lens, including the cornea, anterior chamber, iris
and ciliary body.


ANTIMETROPIA
A condition in which one eye is myopic and the fellow eye is hyperopic.


ANTIOXIDANTS
Micro-nutrients that destroy or neutralize free radicals.


AOA
See American Optometric Association.




                                                                                               16
APHAKIA
The absence of the eye's natural crystalline lens, usually after cataract removal.


APHAKIC SPECTACLES
Thick, plus-powered eyeglasses that were once the standard correction for optical power
following extraction of cataract. The glasses were cumbersome and greatly distorted
peripheral vision. Today, an intraocular lens (IOL) is implanted in the eye after the cataract is
removed.


AQUEOUS FLUID
See aqueous humor.


AQUEOUS HUMOR
Clear watery fluid that flows between and nourishes the lens and the cornea. It is secreted by
the ciliary processes.


ARGON LASER
Laser light produced from argon gas. The main wavelengths are 488.0 nm blue and 514.5-
nm pea green light, but nine separate wavelengths in the blue-green visible light spectrum
are produced.


ARMD
See Age-Related Macular Degeneration.


ASCRS
See American Society for Cataract and Refractive Surgery.


ASTIGMATIC KERATOTOMY
A surgical procedure in which microscopic incisions are placed in the peripheral cornea to
create a more spherical shape. Similar to Radial Keratotomy.


ASTIGMATISM
A condition in which the surface of the cornea is not spherical, but is irregularly shaped like
the back of a spoon. An astigmatic cornea causes light images to focus on two separate
points in the eye, creating a distorted image. Symptoms range from visual discomfort in mild
cases, to severe blurring, ghosting, and distortion similar to a reflection in a fun-house mirror.
The amount of astigmatism you have will appear in the second number of most glasses
prescriptions. The angle of direction (cylinder meridian or axis) of the astigmatism will be
shown in degrees. A prescription of -4.00-1.00x30°, would indicate that you have 1.00 diopter
of astigmatism at 30 degrees axis.



                                                                                               17
ATOPY
A type of inherited allergic response involving elevated immunoglobulin E. Sometimes called
a reagin response, it means that you have hay fever, bronchial asthma, or skin problems like
urticaria or eczema. It can also be acquired, sometimes following hepatitis or extended
contact with solvents or alcohol.


ANTERIOR CHAMBER
The anterior chamber is in the front of the eye behind the cornea and in front of the iris.


AUTOMATED LAMELLAR KERATOPLASTY
An incisional refractive surgery technique for low to moderate myopia (nearsighted,
shortsighted vision). In the procedure, the refractive surgeon places an instrument called an
automated microkeratome on the eye which removes, in a shaving motion, a thin layer of
cornea only microns thick. An even thinner layer of cornea underneath this top cap is
removed, and the top cap is replaced. The procedure does not require sutures.


AUTOMATED PERIMETER
A computer-driven device used to plot defects in the visual field. Usually the patient's head is
placed into this large hemisphere shell. Various points of lights, sometimes of different sizes,
intensities, and colors are projected onto the screen. The patient then indicates whether the
light is seen and the response is recorded. The computer then plots the effective visual
thresholds within the targeted visual field.




B
B SCAN
Ultrasonic procedure used to check for abnormalities or locate foreign bodies within the eye.


BARRAQUER CYRO-LATHE
An instrument used in performing refractive surgery to correct extreme myopia (nearsighted,
shortsighted vision) or hyperopia (farsighted, longsighted vision).


BASEMENT MEMBRANE
A membrane of tissue beneath the epithelium that helps adhere the epithelium to the
Bowman's layer or stromal tissue.




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BAUSCH & LOMB
Ophthalmic equipment company. Click here to go to website.


BCVA
See Best Corrected Visual Acuity.


BEST CORRECTED VISUAL ACUITY
This is a measure of best acuity while wearing corrective lenses like glasses or contact
lenses.


BIFOCALS
Corrective lenses that have two powers of correction. Typically the majority of the lens is
corrected for distance vision while a small area is corrected for near vision. Bifocals and
trifocals are normally prescribed for individuals with presbyopia.


BINOCULAR
Both eyes.


BINOCULAR VISION
The blending of the separate images seen by each of two eyes into a single image. Normal
binocular vision yields a stereoscopic image and parallax-induced depth perception.


BLACK BOX LASER
Common term used for a laser built by its owner or by a firm not approved by the FDA.


BLEPHARITIS
A chronic or long term inflammation of the eyelids and eyelashes, affecting people of all
ages. Among the most common causes are poor eyelid hygiene; excess oil produced by the
glands in the eyelids; a bacterial infection; or an allergic reaction.


BLIND SPOT
(1) A small area of the retina where the optic nerve enters the eye; occurs normally in all
eyes.
(2) Any gap in the visual field corresponding to an area of the retina where no visual cells are
present. Associated with eye disease.


BOARD CERTIFIED
See American Board of Ophthalmology.




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BOWMAN'S LAYER
A layer of cells of the cornea between the epithelium and stroma. The Bowman's layer
appears to be without specific purpose.


BROADBEAM
This is a method of applying excimer laser energy. A beam of energy is applied across the
entire ablation zone at one time. See also variable spot and flying spot.


BUTTONHOLE FLAP
A complication of LASIK caused when the microkeratome breaks through the top of the
cornea while creating a flap of corneal tissue. Buttonhole flaps are most often caused by loss
of suction of the ring that holds the microkeratome to the eye. The usual response is to stop
the surgery, replace the flap, protect the flap with a contact bandage for a few days, then
about three months later do the surgery again. The vast majority of people who have
buttonhole flaps have no long-term problems at all and are able to have LASIK after the flap
has sufficiently healed.




C
C3-R
See Corneal Collagen Crosslinking with Riboflavin.


C-CAP
See Custom Contoured Ablation Pattern.


CALHOUN VISION
Manufacturer of light adjustable intraocular lens.


CANTHUS
Demarcation between the sclera and nasal corner of the eye.




                                                                                            20
CAT ARACT
Also known as nuclear sclerosis. Cataracts are an opacity or clouding of the natural
crystalline lens that may prevent a clear image from forming on the retina. Cataracts occur
naturally and can be induced by trauma. The cataractous lens may require surgical removal
if visual loss becomes significant, with lost optical power replaced with an intraocular lens.


CENTRAL ISLAND
A complication of excimer laser assisted refractive surgery where the laser fails to remove a
portion of cornea. If one views the concave area of the ablation like a lake, one can imagine
an island sticking up in the center. Visual symptoms are typically monocular diplopia or
distortion.


CENTRAL RETINAL ARTERY
The blood vessel that carries blood into eye; supplies nutrition to the retina.


CENTRAL RETINAL VEIN
The blood vessel that carries blood from the retina.


CENTRAL VISION
See visual acuity.


CHOROID
The layer filled with blood vessels that nourishes the retina; part of the uvea.


CILIARY MUSCLES
The muscles that relax the zonules to enable the crystalline lens to change shape for
focusing.


CILIARY PROCESSES
The extensions or projections of the ciliary body that secrete aqueous humor.


CK
See Conductive Keratoplasty.


CLAPIKS
See Contact Lens Assisted Pharmacologically Induced Kerato Steepening.




                                                                                             21
CLE
See Refractive Lens Exchange.


CLEAR LENS EXCHANGE
See Refractive Lens Exchange.


CLEAR LENS REPLACEMENT
See Refractive Lens Exchange.


CLINICAL TRIAL
An investigative process under the jurisdiction of the FDA whereby device or medicine
manufacturers sponsor experiments on people for the purpose of proving or disproving that
the device or medicine performs as expected.


CLR
See Refractive Lens Exchange.


COHERENT MEDICAL GROUP
Ophthalmic equipment company. Click here to go to website.


COLLARETTE
Color ring around the pupil.


COLOR VISION
The ability to perceive differences in color, including hue, saturation and brightness.


COMANAGEMENT
When two or more medical providers provide care to a patient. In refractive surgery it is
common for an optometrist to provide preoperative testing and postoperative care with an
ophthalmologist providing only the surgery.


COMPLEX WAVEFRONT RETREATMENT
A secondary surgery using wavefront-guided ablation in an attempt to reduce higher order
aberrations induced by previous surgery. Complex Wavefront Retreatment is an off-label use
of the excimer laser.




                                                                                            22
CONCAVE LENS
A lens with a hollow shape like the inside surface of a ball. Concave lenses are minus power
lenses and are used to correct myopia (nearsighted, shortsighted vision).


CONDUCTIVE KERATOPLASTY
A refractive surgery procedure for hyperopia and astigmatism that uses a probe to apply high
frequency radio waves into the corneal tissue, causing shrinkage. This controlled shrinkage
will reshape the cornea to accommodate refractive error.


CONE CELLS
One type of specialized light sensitive cells (photoreceptors) in the retina that provides sharp
central vision and color vision. Also, see rods.


CONFORMER
Plastic or silicone shell usually inserted after eye removal to help form the socket and
support the eyelids.


CONJUNCTIVA
The thin transparent mucous membrane that lines the inner surface of the eyelid and covers
the white surface of the eye.


CONJUNCTIVITIS
Inflammation of the conjunctiva. May be caused by bacteria, virus, allergens, or chemical or
ultraviolet light exposure.


CONTACT LENS
Lens made of glass or plastic designed to maintain contact on the surface of the cornea.
Usually used to correct refractive error.


CONTACT LENS ASSISTED PHARMACOLOGICALLY INDUCED KERATO STEEPENING
A process of accommodating hyperopic overcorrection following Lasik, PRK and RK, by
molding the cornea with a tight fitting contact lens and nonsteroidal anti-inflammatory drugs.


CONTACT LENS DISINFECTANT
An agent that kills surface bacteria and microorganisms on contact lenses.




                                                                                              23
CONTACT LENS, DAILY WEAR
Contact lenses designed to be worn only during waking hours. Frequent & planned
replacement contact lenses general term used to refer to contact lens regimens in which
lenses are replaced on a planned schedule, either every two weeks, monthly or quarterly.


CONTACT LENS, DISPOSABLE
Contact lenses defined by the U.S. Food and Drug Administration as a contact lens that is
used one time and discarded. These can be worn either for a single day or up to seven days,
depending on wear schedule prescribed by the eye care professional. Any lens that is
intended to be removed from the eye, cleaned, rinsed, disinfected, and reinserted does not
qualify for inclusion in this category.


CONTACT LENS, EXTENDED WEAR
Contact lenses designed to be worn around-the-clock for intervals of one to seven days.


CONTACT LENS, THERAPEUTIC
Contact lenses designed to aid in protecting and helping a sick eye to heal. These unique
lenses are frequently combined with precise medication delivery schedules to heal the eye.


CONTACT LENS, TORIC
Contact lenses designed to correct astigmatic refractive errors. Toric lenses are weighted to
maintain a specific axis across the cornea.


CONTRAST SENSITIVITY
The ability to perceive differences between an object and its background.


CONVERGENCE/DIVERGENCE
The turning of the eyes inward/outward so that they are both "aimed" toward the object being
viewed.


CONVEX LENS
A lens with a bulging surface like the outer surface of a ball. Convex lenses are plus power
lenses and are used to correct hyperopia or farsightedness. Also used for reading glasses as
required for presbyopia.




                                                                                             24
CORNEA
The outer, transparent, dome-like structure that covers the iris, pupil, and anterior chamber.
The cornea provides approximately two-thirds of the optical power of the eye. Light passes
into the eye through the cornea allowing vision. Light also passes out of the eye allowing the
iris and pupil of the eye to be seen. The cornea can be considered to have five layers:
1. Corneal epithelium
2. Bowman's layer
3. Corneal stroma
4. Descemet's layer
5. Corneal endothelium.


CORNEAL ABRASION
A scratch or similar trauma to the outer surface of the cornea.


CORNEAL COLLAGEN CROSSLINKING WITH RIBOFLAVIN
Used as a therapeutic treatment for keratoconus and corneas that have become unstable or
weak due to ectasia, Corneal Collagen Crosslinking with Riboflavin (C3-R) is a technique
where the eye is flooded with a riboflavin solution and exposed to ultra high frequency light.
C3-R causes the collagen fibrils to thicken, stiffen, and reattach to each other, making the
cornea stronger and more stable.


CORNEAL ENDOTHELIAL CELL DYSTROPHY
Also known as Fuch's Dystrophy, a progressive hereditary disease when moisture in the
cornea is unable to evaporate properly, sometimes causing distortion of the cornea, irregular
refractive error, and epithelial blisters.


CORNEAL HAZE
When the cornea becomes cloudy with opaque white cells, creating vision that is similar to
looking through fog.


CORNEAL REFRACTIVE THERAPY
A temporary non-surgical process of wearing rigid gas permeable contact lenses in an
attempt to reshape the cornea and reduce the need for corrective lenses. Essentially
orthokeratology.


CORNEAL REMODELING
The healing of a wound of the cornea.


CORNEAL TOPOGRAPHICAL MAP
A map of the corneal topography that shows the surface profile of the cornea.




                                                                                             25
CORNEAL TOPOGRAPHY
A process of mapping the surface details of the cornea with a unique camera/computer
combination.


COUNCIL FOR REFRACTIVE SURGERY QUALITY ASSURANCE
A nonprofit consumer/patient organization that certifies refractive surgeons based upon
refractive surgery outcomes and educates the public about refractive surgery issues. Click
here to go to website.


CREDENTIALS
In the healthcare industry credentials means the education, licensure, and professional
history of a healthcare provider.


CRSQA
See Council for Refractive Surgery Quality Assurance. Pronounced "SURS-kah".


CRT
See Corneal Refractive Therapy.


CRYSTALENS
An intraocular lens that is designed to change focus from distant to near objects. It is the first
of its kind to achieve FDA approval.


CRYSTALLINE LENS
The natural lens of the eye, located behind the iris, which helps bring rays of light to focus on
the retina. The original state of the lens is transparent, but the lens becomes cloudy with age
(cataract). The lens has the ability to vary its power to accommodatively focus light from
objects closer than optical infinity.


CUSTOM CONTOURED ABLATION PATTERN
The customization of laser vision correction treatments for decentered ablations and similar
corneal aberrations. The Food and Drug Administration has approved the use of Custom
Contoured Ablation Pattern (C-CAP) method under a Humanitarian Device Exemption.
C-CAP uses a liquid material that is applied to the outside of the eye. In some cases, a
contact lens is applied over the liquid to give a smooth surface. The liquid becomes more
firm, and the contact (if used) is removed. A broadbeam laser applies energy to the entire
treatment area with each pulse. The liquid ablates at the same rate as corneal tissue. As the
laser removes tissue and the liquid, the high areas of the cornea are exposed and ablated
down to the lowest areas. C-CAP has been shown to resolve many topographical
imperfections caused by disease, trauma, or surgery.




                                                                                                26
CUSTOM CORNEA
The trade name for the use of a wavefront guided custom ablation with the LADARVision
excimer laser built by Alcon. Click here to go to website.


CUSTOMVUE
The trade name for the use of wavefront-guided custom ablation with the AMO S4 excimer
laser.


CWR
See Complex Wavefront Retreatment


CYCLOPEGIC REFRACTION
An examination of the eye to determine refractive error while the natural crystalline lens of
the eye is paralyzed and unable to accommodate.


CYCLOROTATION
See Cyclotorsion.


CYCLOTORSION
When eyes rotate clockwise or counterclockwise. This often occurs when a person changes
from vertical (standing or sitting up) to horizontal (lying down) position.




                                                                                                27
D
DAY BLINDNESS
Common term for Hemeralopia.


DECENTRATION
A complication of refractive surgery. In perfect centration, the center of the corneal ablation
exactly coincides with the center of the visual axis and/or pupil. This is like looking through
the very center of your spectacle lens. If you look through the periphery of your lens, you
might end up seeing partly through the lens and partly through the edge of the lens - this is
decentration. Decentration can cause various symptoms including edge glare or even
monocular double vision. Other factors such as the normal size of the pupil, whether it is dark
out (your pupil will enlarge), or the size of the ablation zone will affect the severity or
presence of symptoms.


DEEP LAMELLAR ENDOTHELIAL KERATOPLASTY
An endothelial cell transplant technique wherein a disk of endothelial cell tissue is removed
from a donor cornea and placed on the underside of the recipient cornea, replacing a disk of
endothelial cell tissue of equal size that has been removed from the recipient. The disk can
be created with a mechanical device, or with the femtosecond laser. Deep Lamellar
Endothelial Keratoplasty is an alternative to Penetrating Keratoplasty, which requires the full
thickness of the cornea to be replaced.

DESCEMET'S LAYER
Layer of cells in the cornea above the corneal endothelium.


DEPTH PERCEPTION
The ability of the vision system to perceive the relative positions of objects in the visual field.
This ability to determine the distance of an object is provided by the two eyes receiving
slightly different images due to their wide positioning on the face. The two images are
compared by the brain to calculate distance.


DIABETES MELLITUS
A chronic metabolic disorder characterized by a lack of insulin secretion and/or increased
cellular resistance to insulin, resulting in elevated blood levels of simple sugars (glucose) and
including complications involving damage to the eyes, kidneys, nervous system and vascular
system.


DIABETES TYPE I
Insulin dependent, resulting from destruction of the insulin producing pancreatic islet cells.




                                                                                                  28
DIABETES TYPE II
Non-insulin dependent, resulting from tissue resistance to insulin.


DIABETIC RETINOPATHY
Diabetic retinopathy damages the tiny blood vessels that supply the retina. In the early
stages of this disease-called non-proliferative or "background" retinopathy, the retinal vessels
weaken and develop bulges that may leak blood or fluid into the surrounding tissue.


DIFFUSE LAMELLAR KERATITIS
Also called Sands of Sahara due to the appearance of dunes of sand in the cornea with
advanced stages. DLK is an inflammation under the Lasik flap of the cornea which is
believed to be caused by a response to the presence of sterile infiltrates in the flap interface.
The complication occurs in the early post-operative period, vision is hazy and the eye is
painful and teary. There is also an intolerance of bright light.


DILATION
A process by which the pupil is enlarged. Allows more light to the interior of the eye.


DIOPTER
A unit of measure of the refractive power of a lens. A one-diopter lens will focus parallel light
rays one meter from the lens and a two-diopter lens will focus one-half of a meter from the
lens. A plus 1.0 diopter lens is convex and will converge the light rays so they focus as a
visible image 1 meter past the lens. A minus 1.0 diopter lens is concave and will diverge or
spread light. The minus lens will not actually focus as a visible image on an optics table. Its
image is known as a virtual image and if the diverging rays were followed to their point of
origin, they would focus one meter in front of the minus lens.


DIPLOPIA
A condition in which a single object is perceived as two; also called double vision. Usually
with both eyes open as in binocular diplopia, but can be with only one eye as in monocular
diplopia.


DISPENSING OPTICIAN
See Optician.


DLK
See Diffuse Lamellar Keratitis.


DO
See Doctorate of Osteopathy.



                                                                                                29
DOCTORATE OF OSTEOPATHY
A certificate affirming that the holder has achieved the training required to be a medical
doctor through a school of osteopathy.


DOMINANT EYE
The dominant eye is the eye that looks directly at an object. The non-dominant eye is the eye
that looks at an object from the side.


DOUBLE IMAGE
Also called ghosting. If you look at a clock and some of the numbers have a lighter image
just off to the side, this is a typical double image problem.


DRUSEN
Tiny yellow or white deposits in the retina or optic nerve head.


DRY EYE
The term dry eye is used to describe a variety of ocular disorders with diverse
aetiopathogenesis but similar symptoms: discomfort, a feeling of dryness, burning or
stinging, grittiness, foreign body sensation and photophobia.


DYSTROPHY
The term used to describe a wasting or weakening of biological material, such as corneal
endothelial dystrophy (also known as Fuch's Dystrophy) being the wasting or weakening of
the endothelium.




                                                                                             30
E
EBMD
See Anterior Basement Membrane Dystrophy.


ECCE
See Extracapsular Cataract Extraction.


ECTASIA
An outward bulging of the cornea due to internal pressures and/or a cornea weakened by
surgery.


EDEMA
Swelling.


EMMETROPIA
Refractive condition in which no refractive error is present and distant images are focused
sharply on the retina with no need for corrective lenses. Perfect vision or 20/20.


ENDO
A prefix meaning within or inside.


ENDOPHTHALMITIS
An inflammation within the eye. Inflammations may be caused by organisms such as bacteria
or may be sterile as in immune disorders. Endophthalmitis usually indicates an infectious
disease, but occasionally occurs as a complication of surgery.


ENDOTHELIUM
The inner layer of cells on the inside surface of the cornea.


ENHANCEMENT
Secondary refractive surgery treatments made to refine or improve the original visual result.
Outcome predictability is reduced at higher corrections. Higher corrections and wider optical
zones require deeper sculpting and consequently undercorrection and overcorrection are
more common. Enhancement treatment by contrast is usually a small correction and usually
has higher outcome predictability.




                                                                                              31
ENUCLEATION
Surgical removal of the eye.


EPHIPHORA
A watering of the eyes due to excessive secretion of tears or to obstruction of the lacrimal
passages.


EPIKERATOME
A mechanical device similar to a microkeratome that uses a blunt separator rather than a
sharp blade to produce an epithelial sheet for Epi-LASIK. Rather than a more destructive
alcohol mixture to loosen the epithelial cells used in LASEK. The epithelial cells are moved
over the treatment area after excimer laser energy has been applied.


EPI-LASIK
Modified LASEK with the epithelial cells removed by a mechanical microkeratome using a
blunt, rather than sharp, blade.


EPITHELIUM
The outer surface layer of the cornea, like the epidermis or outer layer of the skin.


EPITHELIUM BASEMENT MEMBRANE DYSTROPHY
See Anterior Basement Membrane Dystrophy.


EPITHELIAL INGROWTH
A complication of refractive surgery when epithelial cells under the flap begin to grow and
multiply causing visual abnormalities and if severe, loss of visual acuity. The most common
treatment is lifting the flap, removing the cells, irrigation of the interface, and repositioning of
the flap.


ESOPHORIA
The position of the eyes in an over-converged position compensated by the external eye
muscles so that the eyes do not appear turned inward.


ESOTROPIA
The position of the eyes in an over-converged position so that the non-fixating eye is turned
inward.




                                                                                                   32
EXCIMER LASER
An argon-fluoride laser that emits ultraviolet light that is emitted in pulses at a wavelength of
193 nm. The term Excimer comes from the concept of an energized molecule with two
identical components or excited dimer (contracted to one word exci-mer). Each pulse of this
"cool" laser removes 1/4000 millimeter of tissue from the targeted surface by breaking
intra molecular bonds in collagen molecules. It would take about 200 pulses from an Excimer
laser to cut a human hair in half. This laser was originally developed for use in the
microprocessor industry and later found its application in vision correction.


EXOPHORIA
The position of the eyes in an over diverged position compensated by the external eye
muscles so that the eyes do not appear turned outward.


EXOTROPIA
The position of the eyes in an over diverged position so that non-fixating eye is turned
outward.


EXTERNAL OCULAR MUSCLES
The six muscles that turn the eyes to position them for viewing.


EXTRACAPSULAR CATARACT EXTRACTION
A surgical procedure that removes the cataractous lens of the eye but leaves the posterior
lens capsule intact.




F
FACS
See Fellow of the American College of Eye Surgeons.


FARSIGHTEDNESS
Common term for hyperopia.


FDA
See Food and Drug Administration.




                                                                                               33
FLAP & ZAP
Slang term for LASIK.


FEMTOSECOND LASER
An infrared range laser that delivers pulses of energy within the cornea, causing a small
controlled explosion of gas that separates the layers of the cornea. The femtosecond laser
for ophthalmology use on the eye is used to create a LASIK flap in a procedure commonly
called "all laser Lasik".


FLUORESCEIN ANGIOGRAPHY
A test to examine blood vessels in the retina, choroid, and iris. A special dye is injected into a
vein in the arm and pictures are taken as the dye passes through blood vessels in the eye.


FLUORESCEIN STAINING
A tiny amount of a fluorescein dye is placed in the tear film. The color will make microscopic
dots appear where the eye has become dry. Excessive staining is an indication of dry eye.


FLYING SPOT
This is a method of applying excimer laser energy. Rather than applying all excimer energy
in a broadbeam across the entire ablation area, or the energy in variable spots sizes across
the ablation area, a very small spot of excimer energy is applied in rapid succession at
different locations across the ablation area.


FOCUSING POWER OF THE EYE
As light enters our eye, it must be brought to a focus on the retina in order to perceive a clear
image. About two thirds of the focusing power of the eye comes from the cornea, the rest
comes from the lens inside the eye. As the light enters the eye, it is focused a fixed amount
by the cornea. As the light passes through the pupil, the lens then adjusts the focus a
variable amount with the exact amount of focusing power applied dependent on the distance
of the object being viewed. Objects at near like a book or knitting require more power than
distance objects like movies or traffic signs.


FOOD AND DRUG ADMINISTRATION
The federal agency of the United States government responsible for the evaluation and
approval of medical devices. The FDA does not evaluate surgical procedures that do not
require a new medical device. Click here to go to website.

FOVEA
The central part of the macula that provides the sharpest vision.




                                                                                               34
FREERADICAL
Molecules that have been implicated as one causative factor in the stimulation of abnormal
cellular reproduction (cancer) and cellular destruction (aging).


FUCH'S DYSTROPHY
See Corneal Endothelial Cell Dystrophy.


FUNCTIONAL VISUAL DISABILITY
The degree to which a visual error interferes with a person's ability to perform normal daily
activities, such as reading, driving at night, or performing hobbies.


FUNDUS
The interior lining of the eyeball, including the retina, optic disc, and macula. This portion of
the inner eye can be seen during an eye examination by looking through the pupil.




G
GAUSSIAN
This is a profile of how excimer energy is applied. Used primarily on flying spot lasers, more
energy is applied to the center of the spot than at the outer edges.


GHOSTING
This is a common term for double images. If you look at a clock and some of the numbers
have a lighter ghost image just off to the side, this is ghosting.


GLAUCOMA
A disease characterized by increased pressure within the eyeball. If not diagnosed and
treated, glaucoma may lead to optic nerve damage, loss of visual field, gradual vision
impairment, and sometimes blindness.


GONIOSCOPY
A diagnostic procedure using a mirror/lens device placed directly upon the cornea that is
used to view the drainage area through which aqueous fluid exits the eyeball.




                                                                                                    35
GRAY BOX LASER
Common term used for a laser imported from outside the United States. This type of
acquisition is not approved by the FDA.




H
HALOS
A known complication of refractive surgery that causes images from light sources to blur with
circles radiating out from the center. Halos also occur naturally without refractive surgery.


HAPTICS
Extensions of plastic from the lens portion of an intraocular lens (IOL) that position and
center the IOL within the eye.


HAZE
An opacification or cloudiness of the normally clear cornea. Any build up of inflammatory
infiltrates (white blood cells), extra moisture, scar tissue, or foreign substances (like drugs)
can cause a clouding of the cornea.


HEALTH MAINTENANCE ORGANIZATION
A medical or vision insurance plan that requires beneficiaries to use only the facilities and
physicians who have contracted with the plan to provide services to beneficiaries. Care
provided to a patient by a facility or physician that is not contracted by the Health
Maintenance Organization is not normally a covered benefit of the plan, except in some
emergency situations or with prior authorization from the plan.


HEMERALOPIA
Day blindness. Often caused by clouding or opacity of one or more of the normally clear
ocular tissues.




                                                                                                   36
HIGHER ORDER ABERRATION
A common eye examination and refraction evaluates low order aberrations (LOA). These are
commonly called sphere (myopia or hyperopia) and cylinder (astigmatism). Only a wavefront
diagnosis is able to measure high order aberrations (HOA), which are beyond simple sphere
and cylinder. HOA are represented in mathematical calculations and are therefore infinite.
The more common of these mathematical calculations are Zernike polynomials and have
names like spherical aberration, coma, trefoil, and secondary astigmatism. Ophthalmology
only deals with about the first eight levels of HOA as represented in Zernike.


HMO
See Health Maintenance Organization.


HOA
See Higher Order Aberration.


HUMANITARIAN DEVICE EXEMPTION
A Humanitarian Device Exemption from the Food and Drug Administration authorizes the use
and marketing of a device that is intended to benefit patients in the treatment of conditions
that affect fewer than 4,000 individuals.


HYPEROPIA
Also known as farsightedness or longsightedness. Hyperopia occurs when the eyeball is too
short from front to back, or the eye's focusing mechanism is too weak, causing light rays to
be focused behind, rather than on, the retina. People with hyperopia have difficulty seeing
objects close up. This refractive abnormality requires a plus (positive or convex) lens for
correction. Hyperopia is significantly more difficult to correct with refractive surgery.


HYPOBARIC
Environment with a decrease of atmospheric pressure, such as at high altitude.


HYPOXIA
A deficiency of oxygen supply to a tissue.




                                                                                           37
I
ICL
See Implantable Collamer Lens


ICRS
Intrastromal Corneal Ring Segments (ICRS, trade name Intacs).


IMPLANTABLE COLLAMER LENS
Descriptive trade name for the STAAR Myopic Visian Implantable Collamer Lens (ICL)
indicated for the correction of high refractive error and is intended for placement behind the
iris in the posterior chamber of the phakic eye. Also known as a Phakic Intraocular Lens
(PIOL), the design of the ICL is very similar to that of standard intraocular lenses used for
cataract surgery. However, the ICL has been designed with forward vault to minimize contact
with the central anterior capsule of the crystalline lens. The lens material is a hydrophilic
biocompatible polymer known as Collamer and has a history of safe use in approved
standard posterior chamber intraocular lenses. Outside the United States the ICL is known
as the Implantable Contact Lens. The US Food and Drug Administration rightfully determined
this descriptive name would misinform the public of the nature of the P-IOL.


INTACS
Trade name for Intrastromal Corneal Ring Segments. Small semicircular rings of plastic that
are implanted in the mid-periphery of the cornea to correct myopia (nearsighted, shortsighted
vision) and/or keratoconus.


INTRAOCULAR
Meaning inside the eye.

INTRAOCULAR LENS
A man-made silicone or plastic lens used to replace the natural crystalline lens of the eye.
Used in cataract surgery, Phakic Intraocular Lens (P-IOL) implantation, or Refractive Lens
Exchange.


INTRAOCULAR PRESSURE
Pressure within the eye. High intraocular pressure is called glaucoma.


IRIS
Colored portion of the eye that expands or contracts to control the size of the pupil.




                                                                                               38
INTRAOPERATIVE
Patient care procedures performed during the operation that are ancillary to the actual
surgery. May include monitoring, fluid therapy, medication, transfusion, anesthesia,
radiography, and/or laboratory testing.


INTRASTROMAL CORNEAL RING SEGMENTS
See Intacs.


IOL
See Intraocular Lens.


IOP
See Intraocular Pressure.


ISCHEMIA
A decrease in the blood supply caused by constriction or obstruction of the blood vessels.




J
JCAHO
See Joint Commission on Accreditation of Healthcare Organizations.


JOINT COMMISSION ON ACCREDITATION OF HEALTHCARE ORGANIZATIONS
The Joint Commission evaluates and accredits more than 18,000 health care organizations
and programs in the United States.




                                                                                             39
K
KELOID
An abnormal scaring of damaged tissue.


KERATECTOMY
Surgical excision (removal) of any portion of the cornea.


KERATITIS
Inflammation of the cornea.


KERATO
A prefix indicating relationship to the cornea.


KERATOCONJUNCTIVITIS
An inflammation (infectious or auto-immune) of the cornea and conjunctiva.


KERATOCONUS
A disorder that involves a thinning of the central cornea. The normally round shape of the
cornea becomes distorted. A cone-like bulge develops, resulting in significant visual
impairment.


KERATOMETRY
The measurement of the curvature of the cornea.


KERATOMILEUSIS
A refractive surgical technique where a partial thickness circular flap of cornea is removed,
frozen, reshaped on a lathe and replaced upon the cornea. The lathe can shape either a
convex or a concave lens.


KERATOTOMY
A surgical incision of the cornea as in Radial Keratotomy.


KERAVISION
An ophthalmic device company.




                                                                                                40
L
LACRIMAL GLAND
The small almond-shaped structure that produces tears; located just above the outer corner
of the eye.


LAGOPHTHALMOS
The inability or difficulty closing one's eye. This can be caused by Bell's Palsy, trauma,
neurosurgery, bacterial infection, stroke, and cosmetic surgery. Common symptoms are
severe dry eye and discomfort, corneal ulceration, decrease or loss of vision.


LAL
See Light Adjustable Lens.


LASEK
See Laser Assisted Epithelium Keratomileusis.


LASER
An acronym for Light Amplification by the Stimulated Emission of Radiation. Laser light is
different from ordinary light in that it is composed of one color (wavelength) traveling in one
direction and each light wave is traveling in step with the adjacent wave making the laser
light more powerful by a factor of millions. This energy is carried by the wave in "packets"
called photons.


LASER ASSISTED IN-SITU KERATOMILEUSIS
An advanced laser procedure combining ALK and PRK to reshape the central cornea,
thereby decreasing or eliminating myopia (nearsighted, shortsighted vision), hyperopia
(farsighted, longsighted vision), and astigmatism (irregular cornea). The refractive surgeon
uses an automated microkeratome to shave off a thin, hinged layer of the cornea. This flap is
then lifted like a hinged door and the exposed surface is reshaped using the excimer laser.
After altering the corneal curvature, the flap is replaced and adheres without stitches.


LASER ASSISTED EPITHELIUM KERATOMILEUSIS
Laser Assisted Sub-Epithelium Keratomileusis (LASEK) is the detachment of the epithelium
with the use of an alcohol solution that softens the epithelium and allows it to be rolled back
into a flap. The flap of epithelium is then be repositioned over the cornea following excimer
ablations.




                                                                                                  41
LASERSIGHT
Ophthalmic equipment company. Click here to go to website.


LASER THERMAL KERATOPLASTY
A non-excimer laser refractive surgery. The office-based instrument applies two rings of laser
energy to the midperiphery of the cornea. Each ring gently heats collagen in the cornea to
change corneal shape. The application of energy is accomplished without physically
contacting the cornea with instrumentation or other apparatus.


LASIK
See Laser Assisted In-situ Keratomileusis.


LATTICE DEGENERATION
Lattice degeneration is a hereditary vitreoretinal degeneration of the retina, causing holes
most often in the periphery and possibly leading to retinal detachment. Lattice is commonly
a contraindication for refractive surgery.


LEGAL BLINDNESS
In the U.S., (1) Visual acuity of 20/200 or worse in the better eye with corrective lenses. (2)
Visual field restricted to 20 degrees diameter or less (tunnel vision) in the better eye. Note
these criteria are used to determine eligibility for government disability benefits and do not
necessarily indicate a person's ability to function.


LENS
A transparent double convex (outward curve on both sides) structure between the iris and
the vitreous humor. Two structures of the eye focus light onto the retina. The first is the
cornea or front surface of the eye that provides about 65% of the focusing power of the eye.
The human lens is located behind the iris and in front of the vitreous humor and provides the
remaining focusing power for the eye. In younger patients (usually below age 45) the lens is
able to adjust its power allowing the eye to change its focal length from distance to near.


LENTICULAR ASTIGMATISM
When the crystalline lens is not symmetrical.


LIGHT ADJUSTABLE LENS
An intraocular lens being developed by Calhoun Vision that can adjust its refractive power by
the introduction of high frequency light waves into the eye. In theory, if a patient's refractive
error is not precisely correct after cataract or Refractive Lens Exchange (RLE) surgery, the
lens can be adjusted without removal from the eye.




                                                                                                  42
LIMBUS
The visible borderline between the clear cornea and the white sclera of the eye. The
conjunctival layer that covers the globe also joins at the limbus.


LTK
See Laser Thermal Keratoplasty.


LOW VISION
Visual loss that cannot be corrected with eyeglasses or contact lenses and interferes with
daily living activities.




M
MACRO STRIAE
Wrinkles in the LASIK flap.


MACULA
The small, sensitive area of the central retina; provides vision for fine work and reading.


MACULAR EDEMA
The collection of fluid in and under the macular portion of the retina causing swelling.


MANIFEST REFRACTION
An examination of the eye to determine refractive error while the natural crystalline lens is
able to accommodate.


MASKS
Most older technology excimer laser machines employ different kinds of masks to customize,
refine, and smooth the corneal surface. Many machines have an internal constricting
diaphragm (like a camera f-stop mechanism) as an internal mask. Variable rotation of the
masks is used to deal with astigmatism.




                                                                                                43
MD
See Medical Doctorate.


MEDIAL
Nasal or towards the nose.


MEDICAL DOCTORATE
A certificate affirming that the holder has achieved the training required to be a medical
doctor through a school of medicine.


MEIBOMIAN GLANDS
Large specialized sebaceous glands in the eyelid. There are about 50 glands on the upper
lids and 25 glands on the lower lids. They create and distribute an oily substance called
lipids. Meibomian gland secretions help keep the eye moist. When blinking, the upper lid
comes down, presses on the oil and pulls a sheet of oil upwards, coating the tear layer
beneath to keep it from evaporating.

MEIBOMIAN GLAND DYSFUNCTION
See Meibomitis.


MEIBOMITIS
A dysfunction of the meibomian glands that provide an oily film over natural tears to keep
them from evaporating too quickly.


MESOPIC PUPIL SIZE
The size of a pupil under medium light conditions such as daylight or a well lit room.

MICRO STRIAE
Also called Bowman's Crinkles. Very small wrinkles in the flap caused by Bowman's layer
constricting.


MICRON
A unit of length equal to one-millionth of a meter.




                                                                                             44
MICROKERATOME
A surgical device for creating a flap of corneal tissue used in LASIK and some transplant
techniques. There are two classes of microkeratomes: mechanical and laser. Both are
affixed to the eye by use of a vacuum ring, flatten the cornea with a clear applanation plate,
then cut across the cornea under the plate.
The mechanical microkeratome uses a very sharp and thin metal blade. The femtosecond
laser microkeratome uses amplified light energy to cause tiny bubbles to form at a
predetermined depth. Thousands of these bubbles next to each other create an incision.


MICROPHTHALMIA
Abnormally small size of eye.


MILLIMICRON
A nanometer, or 10 to the -9 power meter. The term millimicron was used before 1967.


MIOSIS
Pupillary constriction.


MONOCULAR
Involving one eye. As example, monocular polyopia is when a person sees multiple images
in one eye.


MONOVISION
A technique to limit the effects of presbyopia by correcting one eye for near vision and the
other for far vision.


MUNNERLYN FORMULA
Named for engineer Charles R. Munnerlyn, Ph.D, who pioneered the technology for vision
correction based on the excimer laser. This is the basic formula to calculate the amount of
tissue that needs to be removed to affect refractive change.


MYDRIASIS
Pupillary dilation.


MYOPIA
Also known as nearsightedness or shortsightedness. Myopia occurs when the eyeball is too
long from front to back, or the eye's focusing mechanism is too strong, causing light rays to
be focused in front, rather than on, the retina. People with myopia have difficulty seeing
objects far away. This refractive abnormality requires a minus (negative or concave) lens for
correction.



                                                                                                 45
N
NANOMETER
Abbreviation is nm. 10 to the -9 power meters. The term nanometer has replaced the term
millimicron that was used before 1967.


NASAL
Toward the nose.


NATIONAL COMMITTEE FOR QUALITY ASSURANCE
An independent, non-profit organization that certifies credentials verification organizations
and accredits managed care organizations.


NATIONAL EYE INSTITUTE
A division of the US federal government's National Institutes of Health. Approximately
threefourths of US eye research funding originates at the National Eye Institute.

NCQA
See National Committee for Quality Assurance.


NEAR POINT OF ACCOMMODATION
The closest point in front of the eyes that an object may be clearly focused.


NEAR POINT OF CONVERGENCE
The maximum extent the two eyes can be turned inward.


NEARSIGHTEDNESS
Common term for myopia.


NEARVISION CK
Trade mark for the use of CK to restore near vision for individuals with presbyopia. The
technique is similar to monovision.


NEI
See National Eye Institute.




                                                                                                46
NEOVASCULARIZATION
The formation of new blood vessels, often fragile and inappropriate for the location. Longterm
use of contact lenses can starve the cornea of oxygen, causing neovascularization as
the body attempts to provide oxygen through blood vessels.


NUCLEAR SCLEROSIS
Commonly known as cataracts. Nuclear sclerosis is an opacity or clouding of the natural
crystalline lens that may prevent a clear image from forming on the retina. Cataracts occur
naturally and can be induced by trauma. The cataractous lens may require surgical removal
if visual loss becomes significant, with lost optical power replaced with an intraocular lens.


NIDEK
Ophthalmic equipment company. Click here to go to website.


NIGHT BLINDNESS
Common term for nyctalopia.


NYCTALOPIA
Night blindness. Often caused by a deficiency of the retina due to a lack of vitamin A.

NYSTAGMUS
An eye condition characterized by rapid, jerky eye movements.




                                                                                             47
O
OCULAR HYPERTENSION
Elevated intraocular pressure.


OCULAR ROSACEA
The cause of ocular rosacea is not understood but its symptoms can leave the eyes feeling
irritated and "gritty". Patients may experience redness, tearing or crusting on the lashes.


OFF LABEL USE
A term used for procedures that are legal, but are not specifically approved for a particular
device or drug. An example is LASIK. Some excimer lasers are FDA approved for PRK, but
not for LASIK, which is a combination of ALK and PRK. The LASIK procedure comes under
the definition of the practice of medicine (also called scope of practice), so the FDA does not
necessarily need to approve the use of the excimer laser specifically for LASIK. An easier
example is the scalpel. The scalpel is not specifically approved for all procedures that may
require a scalpel, but if a medical doctor determines the use of this FDA approved tool is
appropriate, then it is okay with the FDA.


OPHTHALMIC
Anything to do with the eye.


OPHTHALMIC IMAGING SYSTEMS
Ophthalmic equipment company. Click here to go to website.


OPHTHALMOLOGIST
A medical doctor who specializes in the diagnosis and medical or surgical treatment of eye
diseases. To become an ophthalmologist one must first obtain a medical degree (M.D. or
D.O. in North America) and then complete further specialty training. A medical degree
typically takes 7 or 8 years university training and a specialist certification an extra 3 years in
the USA or 4 years in Canada. Specialist MD's are usually divided into "medical" and
"surgical" disciplines. Ophthalmology is technically a "surgical" discipline. Some
ophthalmologists chose not to perform surgery and can be called "medical ophthalmologists".
An ophthalmologist may also prescribe eyeglasses and contact lenses.


OPHTHALMOSCOPY
Examination of the internal structures of the eye using an illumination and magnification
system.




                                                                                                48
OPTIC CUP
The white, cup-like area in the center of the optic disk.


OPTIC DISK
The circular area (disk) where the optic nerve connects to the retina. Also known as the optic
nerve head.


OPTIC NERVE
The optic nerve is a bundle of nerve fibers, about the diameter of a pencil, which passes
through the back of the eyeball and connects to the nerve fiber layer of the retina. It can be
observed directly with an instrument called an ophthalmoscope. The optic nerve carries the
visual messages from the photoreceptors of the retina to the brain.


OPTICAL ZONE
The area of the eye through which light passes to the retina. To reach the retina light must
pass through the cornea, aqueous humor, crystalline lens, and vitreous while passing
through the pupil. The optical ablation zone is the area where a laser has created full
refractive error correction. See also Transition Zone.


OPTICIAN
An expert in the art and science of making and fitting glasses. The optician may also
dispense and/or fit contact lenses, depending on local licensing practices.


OPTOMETRIST
A doctor of optometry is a non-medical primary eye health care provider who specializes in
the examination, diagnosis, treatment, management, and prevention of diseases and
disorders of the visual system. Optometrists today most often complete a bachelor of science
degree (with very specific requirements) followed by an optometry degree program that
requires four to eight years to complete. Patient contact begins in the second professional
year with the final year being a full 12-month internship. Many optometrists include the
provision of contact lens and spectacle devices as part of their daily practice. The optometrist
may also prescribe medications, depending on local licensing practices.


ORTHOKERATOLOGY
A non-surgical procedure using contact lenses to alter the shape of the cornea to effect a
change in the refractive error.


OVERCORRECTION
A known complication of refractive surgery where the expected amount of correction is more
than desired. Overcorrection often occurs where healing regresses less vigorously than
predicted.



                                                                                                 49
P
PACHYMETRY
A procedure used to measure the thickness of the cornea.


PAPILLEDEMA
Non-inflammatory swelling/elevation of the optic nerve often due to increased intracranial
pressure or the presence of a tumor.


PELLUCID MARGINAL DEGENERATION
Pellucid marginal degeneration (PMD) is a rare, non-ulcerative thinning disorder involving the
outer edge of the lower portion of the cornea. PMD causes a portion of the cornea to bulge
forward, often first presenting as astigmatism. In contrast to keratoconus, where the greatest
corneal protrusion is in the area of maximal thinning, the greatest corneal protrusion with
PMD is above the area of maximal thinning.


PENETRATING KERATOPLASTY
Abbreviated as PK or PKP. A surgical procedure when a button-like full thickness segment of
the cornea is removed and replaced with a donor cornea from another person; a corneal
transplant.


PERIPHERAL VISION
The ability to see objects and movements outside of the direct line of vision.


PERIOPERATIVE
Pertaining to the period extending from the time of hospitalization or admittance for surgery
to the time of discharge.


PERK STUDY
A multi-center study of radial keratotomy (RK) outcomes funded by the National Eye Institute.
Ten-year results of RK patients who had the surgery in 1983 were published in Archives of
Ophthalmology in October 1994.
The study found that seven out of ten patients who had the operation on both eyes no longer
wore or required corrective lenses ten years after surgery, and 85% of patients saw 20/40 or
better without glasses. It concluded that RK is a "reasonably safe operation" that can
"effectively reduce but not eliminate myopia" (nearsighted, shortsighted vision).
The study also found that 43% of patients experienced a hyperopic shift following surgery
over the ten-year period. These patients typically experienced an improvement in their vision
as their refractive error moved closer to 20/20. It is for this reason that ophthalmic doctors will
often intentionally undercorrect their patients, then monitor the rate of healing before



                                                                                                50
performing a follow-up enhancement procedure.
Patients whose vision had achieved full correction or near full correction through surgery and
who experience a hyperopic shift could become farsighted and need to wear glasses.


PHACOEMULSIFICATION
A cataract surgical procedure which uses an ultrasonic vibration to shatter and break up a
cataractous lens, making it easier to remove. The vibration is delivered by an
irrigationaspiration instrument. In a survey of ASCRS members in 1994, 86% preferred the
phacoemulsification cataract removal technique over the extracapsular cataract extraction
technique. The technique was invented by Charles D. Kelman, MD, and was first published
in 1967.


PHAKIC
Meaning that the natural crystalline lens of the eye is present.


PHAKIC INTRAOCULAR LENS
Abbreviated as P-IOL. Also known as Intraocular Contact Lens and abbreviated as P-IOL.
This is a tiny plastic lens that is placed inside the eye in front of the natural crystalline lens to
provide additional refractive change. A Phakic Intraocular Lens is placed either immediately
behind or in front of the iris.


P-IOL
See Phakic Intraocular Lens.


PHI-MOTION ANGIOGRAPHY
Phi-motion angiography employs a scanning laser to capture rapid-sequence images of
blood vessels underlying the retina.


PHOROPTER
An optical instrument containing many lenses which is used to determine the required power
of glasses or refractive error.


PHOTOTHERAPEUTIC KERATECTOMY
Abbreviated as PTK. The use of an excimer laser to remove surface tissue of the cornea for
medical or optical treatment reasons. Very similar to PRK, but for therapeutic rather than
refractive purposes.




                                                                                                   51
PHOTOABLATION
The "cold" process of tissue removal which occurs with excimer laser radiation in the 200nm
wavelength range. This far-ultraviolet wavelength possess light photons so powerful that the
molecular bonds of the target tissue both break down and have sufficient extra kinetic energy
to fly off the surface; hence ablation. Microscopic pictures show incredibly precise cuts with
no evidence of tissue burning in adjacent tissue.


PHOTOCOAGULATION
The process of tissue destruction accomplished by visible light radiation. Tissue is broken
down by the light and "clots" as if it were cooked.


PHOTOPHOBIA
Sensitivity to light.


PHOTOREFRACTIVE KERATECTOMY
Abbreviated as PRK. A surgical procedure using an excimer laser to reshape the central
cornea to a flattened shape for people who are myopic and a more curved surface for people
who are hyperopic. Photorefractive Keratectomy techniques may also be used to correct
astigmatism.


PHOTOVAPORIZATION
The process of tissue destruction as occurs with infrared light radiation.


PHTHISIS BULBI
Shrinking of eyeball following injury, infection, or disease.


PINGUECULA
A yellowish spot seen on the white of the eye at the junction of the clear cornea and white
sclera of the eye. These lesions are usually caused by ultraviolet radiation. The white surface
of the eye cannot "tan" and therefore cannot protect itself from sunburn.


PINHOLE GLASSES
Used in a diagnostic setting to differentiate whether reduced vision is secondary to
uncorrected refractive error or to disease/amblyopia. By eliminating the peripheral light rays
and concentrating the central bundles of light, the vision can be "sharper". But they have no
therapeutic value. Pinhole glasses can't permanently improve one's vision.


PK
See Penetrating Keratoplasty.




                                                                                              52
PLANO
No refractive error. Normal vision. A diopter of 0.


POINT SPREAD FUNCTION
Often used in wavefront diagnostic analysis. A single round spot of light becomes diffused
when it passes through an aberrated element such as a human eye. Aberrations cause some
of the light to spread beyond the boundaries of the light source, causing the dot of light to
appear fuzzy. Analysis of the diffusion of light (spread) helps doctors determine what
changes may be made to remove aberrations causing the diffusion.


POLYNOMIAL
See Zernike Polynomial.


POLYOPIA
Two or more images. Monocular polyopia would be when a person sees multiple images in
one eye. Monocular polyopia is commonly described as ghosting or providing a ghost
image. Binocular polyopia is multiple images only when both eyes are used, indicating
strabismus, a misalignment of the eyes. Polyopia may be caused by neurological
dysfunction, disease, or medication.


POSTERIOR
Back surface or behind.


POSTERIOR CAPSULAR OPACIFICATION
Opacification of the posterior lens capsule. Sometimes called a "secondary cataract". Often a
consequence of modern cataract surgery. It occurs when a thin membrane of tissue grows
over the remaining capsule following cataract surgery, and can develop in as many as half of
all cases between several months and several years after surgery. Most often treated using
the YAG laser to ablate a hole in the capsule.


POSTERIOR CHAMBER
The space between the back of the iris and the front face of the vitreous; filled with aqueous
fluid.


POSTERIOR OPTICAL SEGMENT
The part of the eye behind to the crystalline lens, including the vitreous, choroid, retina, and
optic nerve.




                                                                                               53
POSTERIOR VITREOUS DETACHMENT
The separation of the vitreous body from the retinal surface due to shrinkage from
degenerative or inflammatory conditions or trauma. Often an age-related condition.


PPO
See Preferred Provider Organization.


PREFERRED PROVIDER ORGANIZATION
A medical or vision insurance plan that entices beneficiaries to use only the facilities and
physicians who have contracted with the plan to provide services to beneficiaries by creating
a financial disincentive if the beneficiary seeks care outside the plan's panel of providers.
Care provided to a patient by a facility or physician that is not contracted by the Preferred
Provider Organization is normally a covered benefit of the plan, however at a significantly
lower rate than the same care provided by a facility or physician who is a contracted
provider. The exception is in some emergency situations or with prior authorization from the
plan.


PRELEX
See Presbyopic Lens Exchange.


PREOPERATIVE
Pertaining to the period of time before surgery.


PRESBYOPIA
Part of the normal process of aging. As a person becomes older, we begin to lose the
flexibility of the natural crystalline lens of the eye and weakness of the ciliary muscles.
Presbyopia actually starts at about age ten. Most people do not begin to experience the
effects of presbyopia until their forties. This loss of flexibility limits the ability of the eye to
change its point of focus from distance to near. Because of this normal process, people
begin to wear bifocals or other reading corrections. The one advantage of mild myopia
(nearsighted, shortsighted vision) is the ability to remove your glasses after the onset of
presbyopia and continue to read. Mild myopia (nearsighted, shortsighted vision) effectively
counteracts presbyopia. Refractive surgery does not change effects of presbyopia.


PRESBYOPIC LENS EXCHANGE
The term Presbyopic Lens Exchange (PRELEX) was created to describe a Refractive Lens
Exchange with an intraocular lens designed to accommodate presbyopia.




                                                                                                       54
PRESCRIPTION TERMS
Medical prescription terms were originally all written in Latin. Many of the Latin terms
continue to be used today. But eyeglass prescriptions are somewhat different. Common
medical prescription
terms are:
AC (ante cibum) means "before meals"
BID (bis in die) means "twice a day"
GT (gutta) means "drop"
HS (hora somni) means "at bedtime"
OD (oculus dexter) means "right eye"
OS (oculus sinister) means "left eye"
PO (per os) means "by mouth"
PC (post cibum) means "after meals"
PRN (pro re nata) means "as needed"
Q3H (quaque 3 hora) means "every 3 hours"
QD (quaque die) means "every day"
QID (quater in die) means "4 times a day"
Sig (signa) means "write"
TID (ter in die) means "3 times a day"


PRESVIEW
Surgical treatment for presbyopia owned by Refocus Group, Inc., and partnered with CIBA
Vision for distribution. PresVIEW has received European CE Mark approval for the
PresVIEW Scleral Incision System in August 2003. The company has re-engineered the
system for its PresVIEW Scleral Spacing Procedure, which surgically treats presbyopia,
primary open angle glaucoma and ocular hypertension. The updated procedure incorporates
automated components to simplify and enhance placement of Refocus Group's PresVIEW
scleral implants, resulting in greater reproducibility of the procedure by clinicians. Refocus
Group's strategic partner, CIBA Vision, plans a commercial launch of the PresVIEW Scleral
Spacing Procedure in selected European markets by the end of 2003. Refocus Group also
aims to begin FDA Phase II clinical trials of the procedure for presbyopia in late 2003, subject
to FDA approval.


PRISM
A prism is a lens that will bends light towards its base. Prisms are used to measure the angle
of deviation in strabismus to correcting binocular polyopia when the eyes become misaligned
in adulthood. A prism may be included in spectacle correction to help align images.


PRK
See Photorefractive Keratectomy.


PSF
See Point Spread Function.




                                                                                             55
PSEUDOPHAKIC
When the natural crystalline lens of the eye has been replaced with an artificial lens during
cataract surgery or Refractive Lens Exchange.


PTK
See Phototherapeutic Keratectomy.


PTYGERIA
A growth of scar tissue on the cornea. These lesions like pinguecula are caused by an
ultraviolet burn to the surface layer or epithelium.


PUNCTAL OCCLUSION
Closing off the Punctum, either with plugs, cauterization, or other natural or artificial methods.


PUNCTAL PLUGS
Small silicone or plastic plugs that are inserted into any or all of the punctum.


PUNCTUM
Tear drains around the eye. There are two in the upper lid and two in the lower lid.


PUPIL
Appears as a small black dot in the center of the iris. The pupil changes its diameter in
response to changes in ambient lighting. The pupil varies the amount of light reaching the
retina and the depth of focus of the eye.


PUPILLARY RESPONSE
The constriction and dilation of the pupil due to stimulation by light or accommodation.




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R
READERS
See Reading Glasses.


REALLY SIMPLE SYNDICATION
Really Simple Syndication (RSS) is an XML-based format for news distribution that includes
headlines, summaries and links back to a publisher website for the full article. You load RSS
news feeds into a reader or visit them on a personalized web page. RSS keeps you up-to-
the-moment on your favorite news sources, providing an indicator when news breaks.


READING GLASSES
Spectacles that induce a small amount of myopia (nearsighted, shortsighted vision), also
called plus lenses. Reading glasses, often called readers, are used temporarily by individuals
who are presbyopic to assist with near vision. See also bifocals, trifocals, and monovision.


RADIAL
Pertaining to the radius or line from a circle center to the circumference of the circle.


RADIAL KERATOTOMY
Abbreviated as RK. A surgical procedure that permanently alters the shape of the cornea by
placing microscopically thin relaxing incisions in the peripheral cornea. The incisions cause
the central portion of the cornea to flatten, thereby reducing the power of the cornea.


REFRACTEC
Manufacturer of ophthalmic equipment for Conductive Keratoplasty. Click here to go to
website.


REFRACTION
(1) A test to determine the best eyeglasses or contact lenses to correct a refractive error
including myopia (nearsighted, shortsighted vision), hyperopia (farsighted, longsighted
vision), or astigmatism (irregular cornea).
(2) The bending of light by the use of lens or other material.
See also Manifest Refraction and Cycloplegic Refraction.


REFRACTIVE ERROR
The degree to which images received by the eyes are not focused on the retina (myopia,
hyperopia, or astigmatism) measured in diopters.




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REFRACTIVE LENS EXCHANGE
Refractive Lens Exchange (RLE), also known as Clear Lens Exchange (CLE), is essentially
cataract surgery without the cataract. The crystalline lens is removed from the eye and
replaced with a clear plastic intraocular lens (IOL). The new IOL will be of a power to correct
refractive error. Cataract surgery is performed when the crystalline lens has become cloudy.
RLE is performed for purely refractive purposes.


REFRACTIVE SURGERY
Any surgical procedure which permanently alters the focusing power of the eye in order to
change refractive errors. Refractive surgery may include corneal surgery such as LASIK,
LASEK, PRK, Intacs, CK, LTK or lens surgery such as RLE or P-IOL.


REGRESSION
A return by the cornea toward the original refractive state.


RESTASIS
An prescription eye drop with diluted cyclosporine anti-inflammatory used for the treatment of
dry eye and other ocular conditions.


ReSTOR
The brand name for the AcrySof ReSTOR apodized multifocal intraocular lens. The ReSTOR
lens is used with cataract surgery and Refractive Lens Exchange (RLE). The potential
advantage of any multifocal lens is the ability to see clearly objects both near and distant.
ReSTOR attempts to resolve presbyopia.


RETINA
The light sensitive layer of cells (rods and cones) on the inner back surface of the eye that
converts light images into nervous impulses sent along the optic nerve for transmission to the
brain.


RETINAL AXONS
The nerve fiber extensions of the retinal photoreceptors that form the nerve bundle called the
optic nerve.


RETINAL DETACHMENT
A separation of the neural tissue of the retina from the pigmented epithelium layer and
therefore the blood supply. Results in loss of vision in the detached area. Repairable with fair
to good prognosis for vision if diagnosed in the early stages.




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RETINAL PIGMENT EPITHELIUM
The pigment cell layer that nourishes the retinal cells; located just outside the retina and
attached to the choroid.


RETINITIS PIGMENTOSA
The name given to a group of disorders of the retina, all of which result in a progressive
reduction in vision.


RETREATMENT
See Enhancement.


ReZOOM
The brand name for the ReZoom multifocal intraocular lens. The ReZoom lens is used with
cataract surgery and Refractive Lens Exchange (RLE). The potential advantage of any
multifocal lens is the ability to see clearly objects both near and distant. ReZoom attempts to
resolve presbyopia.


RGP
See Rigid Gas Permeable Contact Lens.


RIGID GAS PERMEABLE CONTACT LENS
A hard contact lens that allows significant amount of air to pass through. This type of lens
often provides superior refractive correction to a soft contact lens.


RK
See Radial Keratotomy.


RLE
See Refractive Lens Exchange.


RMS
See Root Mean Square.


RSS
See Really Simple Syndication.




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RODS, ROD CELLS
One type of specialized light sensitive cells (photoreceptors) in the retina that provide side
vision and the ability to see objects in dim light (night vision). Also, see cones.


ROOT MEAN SQUARE
Actually means the root of the mean of the squares and is an evaluative measurement of a
wavefront diagnostic. It describes the smoothness of the surface in terms of deviation from
the ideal spherical wavefront and is calculated using the same technique that is used to
derive standard deviation. As a general rule of thumb, a Root Mean Square value of .30
microns or greater is an indication that a wavefront-guided ablation is necessary to provide a
patient a good refractive surgery outcome.


ROSACEA
See Ocular Rosacea.




S
SALINE SOLUTION
A sterile salt solution used in cleaning, rinsing, and sometimes storing of contact lenses.


SANDS OF SAHARA
See Diffuse Lamellar Keratitis.


SCHLEMM'S CANAL
The passageway for the aqueous fluid to leave the eye.


SCLERA
The tough, white, outer layer (coat) of the eyeball. With the cornea, it protects the entire
eyeball.


SCLERAL SHELL
Flush fitting thin artificial eye usually fit over phthisis bulbi.




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SCOTOPIC PUPIL SIZE
The size of a pupil under low light conditions similar to light in a theater or during night
driving.


SCOTOMA
An area of partial or complete loss of vision surrounded by an area of normal vision.


SECONDARY IMPLANT
If no lens was placed in the eye at the time of cataract removal surgery, then a secondary
procedure to implant an intraocular lens may be completed later.


SEE
See Society for Excellence in Eyecare.


SHIRMER TEST
Tiny strips of filter paper are placed in the patient's eyes just under the lids. After five minutes
the distance the tears have stained the paper is measured. The greater the distance, the
higher the natural tear production.


SIDE VISION
See Peripheral Vision.


SLIT LAMP
A microscope using various magnifications combined with a strong light that can be focused
into a slit for examining the eye.


SNELLEN VISUAL ACUITY TEST
The white chart with the big black E at the top and lines of letters that become increasingly
smaller. The Snellen Test is one of many tests used to determine visual acuity. The term
20/20 means that the patient can see an item 20 feet away with the same clarity that a
normally sighted person can see an item 20 feet away. 20/40 means that the pati ent can see
an item 20 feet away with the clarity that a normally sighted person can see an item 40 feet
away. This is worse than normal vision. 20/10 means that the patient can see an item 20 feet
away with the same clarity that a normally sighted person can see an item 10 feet away.
20/10 is better than normal vision.


SOCIETY FOR EXCELLENCE IN EYECARE
Ophthalmologist membership organization. Click here to go to website.




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SOS
See Sands of Sahara.


SPHERE
Term meaning spherical refractive error of hyperopia or myopia.


SRP
See Surgical Reversal of Presbyopia.


STRABISMUS
More commonly known as crossed-eyes, is a vision condition in which a person cannot align
both eyes simultaneously under normal conditions. One or both of the eyes may turn in, out,
up or down. An eye turn may be constant; when the eye turns all of the time. Strabismus may
be intermittent; turning only some of the time, such as, under stressful situations or when ill.


STARBURSTS
A known complication of refractive surgery that causes images from light sources to blur with
spikes radiating out from the center. Starbursts also occur naturally without refractive
surgery.


STEREOPSIS
The ability to perceive three-dimensional depth due to the distance between a person's two
eyes.


STEROID
A large class of pharmaceutical agents that chemically resemble cholesterol. Two better
known types are anabolic steroids often used in athletics, and glucocorticoid steroids that are
used to reduce inflammation.


STILES-CRAWFORD EFFECT
The Stiles-Crawford effect (discovered in 1933) describes angular dependence of retinal
sensitivity. Rays which enter the pupil near its center, which are parallel to retinal receptors,
are more effective than oblique rays which enter the pupil near its margins. So, the light
passing through the periphery of the pupil is less efficient at stimulating vision than the light
passing near the center of the pupil. It is believed that photoreceptors act as light pipes, and
more light gets down if it enters straight down (through the center of the cornea), rather than
at a large angle (through the periphery of cornea).




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STRIAE
Wrinkles in the corneal flap created for LASIK. There are two kinds, macro striae and micro
striae.


STROMA
Thickest and central layer of cells in the cornea.


SEBORRHEIC DERMATITIS
Seborrheic Dermatitis may involve the presence of somewhat greasy flaking involving the
area around the eyes, nose, presenting with crusts, scales, itching and occasionally burning,
and may also be found on the scalp, ears and torso. Although closely related, it does not
usually involve red bumps as in Rosacea.


SURGICAL REVERSAL OF PRESBYOPIA
A general term used for many different techniques that attempt to cure presbyopia. To date,
none of these techniques have been proven to be safe, effective, and predictable. There are,
however, surgical techniques that offer a "work around" the symptoms of presbyopia,
including monovision.


SULCUS
Upper eyelid depression.


SUMMIT
Ophthalmic equipment company.


SUNRISE TECHNOLOGIES
Ophthalmic equipment company.


SUPERIOR
Upper, as in upper eyelid.


SUPPRESSION
The inability to perceive all of part of objects in the field of vision of one eye.


SURFACE ABLATION
Any surgical procedure that ablates tissue at the surface of the cornea. PRK, LASEK, and
Epi-LASIK are all surface ablation techniques.




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T
TBUT
See Tear Break Up Test.


TEAR BREAK UP TEST
A test that determines the quality of the tears on the eye. The doctor observes the tear film
under the microscope while the patient avoids blinking until tiny dry spots develop. The
longer the amount of time that passes before the tear film breaks up, the more stable the tear
film. A good value is more than 10 seconds.


TEMPORAL
Toward the ear.


TONOMETRY
A procedure for the measurement of the fluid pressure inside the eye (intraocular pressure).
One of the tests for glaucoma.


TOPCON
Ophthalmic equipment company. Click here to go to website.


TOPOGRAPHY-GUIDED REFRACTIVE SURGERY
Uses topography data to guide the laser during refractive surgery.


TOPOGRAPHY
To measure the high and low areas of a plane.


TORIC
A contact lens that is designed to correct sphere and astigmatism. A toric lens is weighted on
the bottom so it will maintain the same axis position of the astigmatic correction.


TRABECULAR MESHWORK
The spongy, mesh-like tissue near the front of the eye that allows the aqueous fluid to flow to
Schlemm's canal then out of the eye through ocular veins.




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TRANSITION ZONE
The area of laser ablation that changes for the full correction of the central ablation zone
optical ablation zone to the original surface depth of the cornea.


TRIFOCALS
Corrective lenses that have three powers of correction. Typically the majority of the lens is
corrected for distance vision while a small area is corrected for near vision and another small
area is corrected for middle vision. Trifocals and bifocals are normally prescribed for
individuals with presbyopia.




U
UCVA
See Uncorrected Visual Acuity.


ULTRASOUND
Procedures using sound waves to measure certain portions or detect abnormalities within the
eye. See A Scan and B Scan.


ULTRAVIOLET RADIATION
Radiant energy with a wavelength just below that of the visible light. UV-c is the shortest
wavelength at 200-280nm and is absorbed by the atmosphere before reaching the surface.
Extremely damaging to living tissue. UV-b, at 280-315nm is "burning rays" of the sun and is
damaging to most living tissue. UV-a, at 315-400nm is "tanning rays" of the sun and is
somewhat damaging to certain tissues. UV radiation has been described as a contributing
factor to the processes that results in ARMD, cataracts, and causes exposure keratitis.


um
Abbreviation meaning 10 to the -6 power meter.


UNCORRECTED VISUAL ACUITY
The best vision measurement taken without the use of glasses or contact lenses.




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UNDERCORRECTION
A complication of refractive surgery where the expected amount of correction is less than
desired. Undercorrection often occurs where healing regresses more vigorously than
predicted.


UVEA, UVEAL TRACT
The middle coat of the eyeball, consisting of the choroid in the back of the eye and the ciliary
body and iris in the front of the eye.




V
VARIABLE SPOT
This is a method of applying excimer laser energy. Rather than applying all excimer energy
in a broadbeam across the entire ablation area, or with a very small flying spot of excimer
energy applied in rapid succession at different locations across the ablation area, the energy
is applied in variable spot sizes across the ablation area.


VISIAN ICL
P-IOL manufactured by STAAR Surgical. Click here to go to website.


VISION THERAPY
A treatment process for the improvement of visual perception and/or coordination of the two
eyes for efficient and comfortable binocular vision (orthopedics, vision training, and eye
exercises).


VISUAL ACUITY
Clearness of vision. The ability to distinguish details and shapes of objects; also called
central vision.


VISUAL AXIS
The central area of the cornea, pupil, and lens that light passes through to reach the retina
and be "seen".




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VISUAL FIELD
The area or extent of space visible to an eye in a given position of gaze. The central visual
field is directly in front and the target at which we are looking. The peripheral visual field is
that which we perceive in our "side vision". The fields of each eye partly overlap.


VITREORETINAL
Involving the vitreous humor, retina, or both.


VITREOUS HUMOR
The transparent, colorless mass of gel that lies behind lens and in front of retina.




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W
WAVE LENGTH
The distance between the top of one wave and the top of the next wave. The length of one
complete wave of the argon fluoride excimer laser is 193 nm. This wavelength is in the far
ultraviolet end of the electromagnetic spectrum.


WAVEFRONT
A technology used in optics that is able to determine and measure high order aberrations.
These aberrations directly relate to an individual's quality of vision.
Conventional eye examinations can detect two types of error on the cornea - spherical
(myopia and hyperopia) and cylindrical (astigmatism). Wavefront diagnostic can detect an
infinite set of ocular aberrations called the Zernike Polynomials, but in ophthalmology
discussion has generally been limited to the first 15 or so.
The wavefront sensor system includes a fixation target, a bundle of input laser beams, a
wavefront sensor that measures the slope of the exiting wavefront, and software that will
determine the characteristics of the excimer ablation.
The visual fixation target assists the patient in maintaining view, direction and
accommodation during the wavefront measurement. While the patient fixates, a bundle of
laser beams is shined into the eye. The light is reflected from the retina back through the
pupil, and the wavefront of the light leaving the pupil is relayed to the wavefront sensor. The
wavefront gets distorted by the refractive properties in the human eye.
When the laser beam bundle enters the eye, it has a flat wavefront. In theory, a perfect
optical system would reflect back a beam bundle with its wavefront still flat. But in a normal
human eye — after the beams of light have traveled through an imperfect crystalline lens, an
irregular cornea and the other ocular media — the flat wavefront has become irregular. Think
of a square grid being projected in and a wavy grid reflecting out.


WAVELIGHT
Ophthalmic equipment company specialising in refractive laser surgery. Click here to go to
website.


WELCH ALLYN
Ophthalmic equipment company. Click here to go to website.


WITH-THE-RULE ASTIGMATISM
"With the rule" astigmatism has an axis of about 180 degrees (when Rx is written in minus
cylinder form). "Against the rule" astigmatism has the axis at about 90 degrees.
Both forms are common. Nevertheless, when looking at population norms, "with the rule" is
more common in young adults while "against the rule" is more common in older adults.




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Y
YAG LASER
YAG is an abbreviation for neodymium yttrium-aluminum-garnet, the material used generate
a short pulsed, high-energy light beam in the infra red wavelength of 1064 nm. The YAG
laser is a surgical instrument that can be precisely focused by computer to cut,
photovaporize, or fragment tissue. The YAG laser is used to treat posterior capsular
opacification; a clouding of the remaining capsular tissue that develops postoperatively in as
many as 75% of cataract removal operations. The tissue is vaporized with carefully
controlled pulses of the YAG laser, and the surgery is performed on an outpatient basis. The
common misconception that "lasers" are used to remove cataracts occurs because
postcataract patients eventually require YAG laser capsulotomy.




Z
ZEISS
Ophthalmic equipment company. Click here to go to website.


ZERNIKE
See Zernike Polynomial.


ZERNIKE POLYNOMIAL
Zernike polynomials are mathematical blueprints of ocular aberrations measured with
wavefront technology. Each Zernike polynomial, called a mode, describes a certain type of
geometric shape, a certain three-dimensional surface. The second-order Zernike terms
represent the conventional aberrations defocus (spherical correction) and astigmatism.
Zernike aberrations above the second order are called higher order aberrations. The third
order Zernike terms are coma (a wavefront shape with twofold symmetry) and trefoil (a
wavefront shape with threefold symmetry). The fourth order Zernike terms include spherical
aberration and four other terms, and so on. The Zernike polynomials are an infinite set, but in
ophthalmology discussion has generally been limited to the first ten or so.


ZYOPTIX
The brand name for wavefront guided custom ablation on the Technolas Perfect Vision
excimer laser. Click here to go to website.




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ZONULES
The fibers that hold the lens suspended in position and enable it to change shape during
accommodation.




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