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                  KARNATAKA, BANGALORE.

                          ANNEXURE II


                      FOR DISSERTATION.

                                 Dr. RAJNA. RASHEED
                                 YENEPOYA MEDICAL COLLEGE
                                 MANGALORE – 575018.

                                 MANGALORE – 575018.


4. DATE OF ADMISSION TO           23-04-2008.

5. TITLE of the TOPIC :



        6.1: NEED FOR THE STUDY:

        The control of postoperative astigmatism is an important challenge which has

received great interest especially in the recent years. When a patient suffers from co-

existing cataract and glaucoma, the choice of surgery may be a combined procedure of

cataract extraction and trabeculectomy as a one-stage procedure to restore visual

rehabilitation and to prevent progressive optic nerve damage. It is well known that post-

operative astigmatism after a seemingly well performed cataract extraction with

intraocular lens implant can result in a degraded quality of vision often leading to patient


        The major determinants of such post-operative astigmatism include the site and

size of incision, the type of suture used and suturing technique and thereby the corneal

distortion induced. Small incisions induce less astigmatism and thereby enhance visual

recovery following SICS. Thus SICS is an answer to the problems related to post-

operative astigmatism.

        Another important determinant of post operative astigmatism is the site of

incision. The closer the incision is to the limbus, the greater the post- operative


       There are differing schools of thought regarding the surgical management when

cataract is complicated by the presence of glaucoma. Some surgeons prefer to operate the

cataract and trabeculectomy separately as compared to a single stage combined

procedure. Both the one stage and two stage procedures have their own adherents. A

combined single stage technique offers early visual restoration and prevents the early

post-operative intra ocular pressure rise that may result from cataract surgery alone while

undergoing surgical insult only once. A two stage procedure however allows the surgeon

to implement newer astigmatically neutral techniques for incision placement and

determining the size of incision to be done.

       Whether the benefit of a small incision holds good in a combined surgery with

trabeculectomy remains undetermined.       The likelihood of postoperative astigmatism

following a trabeculectomy is considered to be less of a problem since the scleral incision

is placed well behind the limbus although the anterior chamber entry is anterior in the

clear cornea. A clear corneal incision approach provides increased safety, decreased

inflammation and pain as well as reduced post operative astigmatism. It would be of great

benefit to know the amount of post-operative astigmatism induced following a combined

cataract and trabeculectomy procedure and efforts can then be made to minimize this


       Very few studies have been undertaken in this regard. The present study is

undertaken to compare the amount of induced astigmatism following Small Incision

Cataract Surgery combined with Trabeculectomy compared to Small Incision Cataract

Surgery alone.


                Cataract is the leading cause of blindness all over the world followed by

glaucoma, age related macular degenerations, diabetic retinopathy and trachoma1. In

many instances patients suffer from cataract with co-existing glaucoma. The only

treatment to date for cataracts is surgical removal of the cataractous lens with

implantation of an IOL to counter the resultant aphakia. Till the middle of the last

century the favoured surgical technique was Extra Capsular Cataract Extraction (ECCE).

Although it was replaced by Intra Capsular Cataract Extraction (ICCE) techniques in the

second half of the twentieth century, the post operative complications of ICCE such as

Retinal Detachment and Endophthalmitis caused the procedure to fall into disrepute and

there was a return to ECCE. Today the technique of ECCE has seen many refinements in

the form of improved instrumentation, equipments and modified surgical steps.

       Corneal Astigmatism has been a by-product of cataract surgery as well as

trabeculectomy since the first corneal incision was made. Patients with post operative

corneal astigmatism account for a large number of such refractive errors and suffer from

delayed visual rehabilitation and limited visual outcome thus reducing the effectiveness

of the procedure. Symptoms such as glare, monocular diplopia, asthenopia and distortion

are accompaniments. Even when corrected with glasses, astigmatism may cause off-axis

blur eyestrain and visual field restriction. Both cataract extraction and trabeculectomy are

known to cause mild to moderate degrees of changes in corneal curvature leading to

post - operative astigmatism, each producing one or the other kind of astigmatism. It is
now well known that cataract surgery produces an increase in vertical corneal radius of

curvature and owes it to the wound gape or wound compression and also may be related

to the size of the incision. In contrast, in trabeculectomy there occurs a reduction in the

corneal radius in the vertical meridian. This difference may be the result of the partial

thickness scleral flap created during trabeculectomy. The surgically produced gap is

overlaid by a scleral flap, which spreads support from the sutures inserted into it over the

whole of wound gape; the more posterior placement of the incision may also explain the

difference in behaviour in comparison with cataract extraction2, 3. Following a combined

procedure there may occur an increase or reduction of the vertical corneal radius of


        In order to minimize the post operative astigmatism, the length and architecture

of the incision, site of incision, types of suture and suture materials have all been

modified over the years. A prime example being the change of surgical techniques from

ICCE to ECCE to SICS to Phacoemulsification. The advent of improved instrumentation

(better blades, canulas and needles) as well as better pre-operative and intra-operative

measurements of astigmatism has led to a series of improvements, which promise to

solve or greatly reduce the problem of induced astigmatism following cataract surgery

and trabeculectomy, in the majority of patients.

        It therefore becomes imperative to study the surgically induced astigmatism

following the various techniques in order to offer the best corrected visual acuity post



       The eye acts as an optical instrument in which the Cornea and the lens act as

focusing system of the eye. Cornea is a highly transparent structure of meniscus form,

approximately 12mm in diameter and slightly smaller vertically than horizontally. The

centre thickness is usually between 0.5 – 0.6mm. The thin pre-corneal tear film covering

the anterior surface is too thin to affect the power appreciably. Both the surfaces of the

cornea are regarded as spherical, the anterior radius of curvature being +7.7mm and

posterior radius of curvature being +6.8mm. The refractive index of the corneal

substance may be taken as 1.376 and that of the aqueous humour, in contact with the

back surface of cornea as 1.336.

       Since the shape of the corneal surface determines its refractive power, even a

minor modification of its surface can lead to a significant alteration of the image formed

on the retina. Consequently efforts have been made to detect and monitor this important

refractive surface. The techniques frequently used to measure the anterior corneal

curvature are Keratometry and Corneal Topography.


       The anterior surface of the cornea is elliptical with an average horizontal diameter

of 11.5mm and vertical diameter of 10.6mm. The posterior surface of the cornea is

circular with an average diameter of 11.5mm. The corneal thickness varies from 0.52mm

at centre to 0.8mm peripherally increasing to about 1.2mm at the limbus. Thus the cornea

has different radii of curvature at different points along the same meridian with central

steepening and peripheral flattening. The central zone occupies the central 4mm of the

cornea and is responsible for forming image at the fovea. The cornea is divided into three

peripheral zones, namely – the Para central zone         which is 4 – 8mm in diameter,

peripheral zone of 8-11mm diameter and a limbal zone of 11- 12mm diameter. The light

entering the eye as a whole is refracted markedly at the anterior corneal surface for two

reasons- the corneal curvature and the difference in refractive indices of air and cornea.

       The aspherical shape of the cornea’s anterior surface is responsible for baseline

astigmatism of 0.25 – 0.5D in almost every human eye.


        Astigmatism is a type of refractive error wherein the refraction varies in different

meridian. As a result of which, the rays of light entering the eye cannot focus on a point

focus but form multiple focal lines.

       Sir Isaac Newton, who himself had been astigmatic, first considered the question

of astigmatism in 1727. This optical error received its first detailed investigation from

the scientist, Thomas Young, in 1801discovered that his astigmatism of 1.7D remained

unchanged on his immersing his head in water and thus eliminating the influence of the

corneal refraction, and so he attributed this defect to the lens. Although Cambridge

astronomer, Airy in 1827, was the first to correct the defect by cylindrical lens it was

   largely the work of Donders in 1864, which impressed the ophthalmic society with the

   prevalence and importance of Astigmatism.


          About 50% of full term infants in their first year of life have astigmatism of over

   1D. The incidence of astigmatism decreases as the child grows and by adulthood about

   15% of the people have astigmatism > 1D and only 2% have astigmatism > 3D.

            The Stenstrom’s study from Uppsala, Sweden, proposed a rough estimate on the

   incidence of Astigmatism:

 Almost all individuals have a minor degree of physiological astigmatism.

 About 60% cases of refractive errors have astigmatism which needs to be corrected.

 Astigmatism occurs with equal frequency in males and females.

 The approximate distribution according to degree of astigmatism is:

   0.25- 0.5D      50%

   0.75- 1.0D      25%

   1.0 - 4.0D      24%

   > 4.0D             1%

 The most common type of astigmatism is compound myopic, followed by compound

   hypermetropic, mixed, simple myopic and simple hypermetropic.

   With the rule           38%

            Against the rule     30%

            Oblique              32%

              Symptoms of Astigmatism include transient blurring of vision, asthenopic

symptoms, tilting of the head, and squinting, burning and itching sensation in the eyes.

When the astigmatism shows a steeper vertical corneal meridian, it is termed with-the-

rule and a steeper horizontal corneal meridian; it is called against-the-rule. Corneal

astigmatism is usually with-the-rule in young eyes and there is a shift toward against-

the-rule with advancing age.4

Investigations include:

a) Retinoscopy – it is the time tested method of estimating the optical state of the eye.

An illuminated area of the retina serves as an object and the image is formed at the far

point of the eye by moving the illumination across the fundus and noting the behavior of

the luminous reflex in the pupil. Conclusions can be drawn regarding the refractive

status of the eye by studying the nature of the rays, emanating from the fundus to form

an illuminated area of the pupil. If the image is formed between the patient and the

observer, the movements of the reflex and the external light are in opposite directions. If

it falls outside the region, either behind the patient’s eye or behind the observer’s eye,

the two move in the same direction. When the far point of the patient’s eye corresponds

to the nodal point of the observer’s eye, a neutral point is reached. The rationale of the

method is to add lenses to the diopteric system of the patient’s eye until the point of

reversal is seen by the observer.

      In Astigmatism, the refractionist has to determine, not only the neutralization

points of the principal meridians but also the orientation of the meridia.

          The various retinoscopes used nowadays are reflecting retinoscopes – may be a

   plane mirror or a combination of plane and concave mirrors like the Priestley- Smith’s

   mirror or self illuminating ones like spot or streak retinoscopes.

   b) Keratometry-the keratometer is used to determine the different corneal curvature in

   the two different meridians which may or may not be orthogonal. It is the measurement

   of the curvature of the anterior surface of cornea across a fixed chord length, usually 2-

   3mm, which lies within the optical spherical zone of the cornea. An ideal keratometer

   must be able to measure the radii in various meridia about the axis of the cornea. To this

   end, instruments are designed that can be rotated with respect to a particular axis. The

   objects are called mires. Various keratometers have been designed such as Helmholtz

   keratometer, Bausch and lomb keratometer, Javal – schiotz keratometer and today there

   are also Surgical keratometers and Automated keratometers.

                  BAUSCH AND LOMB KERATOMETER:                            The working of the

   Reichert (Bausch and Lomb) keratometer is based on the         principle of constant image

   size and variable image size.in order to avoid error due to constant motion of the eyes,

   this doubling device has been introduced.

   Optical system and parts of Bausch and Lomb Keratometer:

 The object is circular mire with two plus and two minus signs.light from the mire strikes

   the patient’s cornea and produces a diminished image behind it. This image then

   becomes the object for the remainder of optical system.

 The objective lens focuses the light from the image of the mire along the central axis.

 Diaphragm and doubling prisms

 Eyepiece lens

               Procedure of Keratometry involves the adjustment of the instrument and

patient, focusing of the mires and the measurement of corneal curvature. The findings in

case of astigmatism are a difference in the power between two principal meridian,

horizontally oval mires in with- the – rule astigmatism and vertically oval mires in

against- the – rule astigmatism.In oblique astigmatism, the principal meridian are

between 3-600 and 120- 1500

c) Astigmatic fan test- fogging technique using astigmatic fan test is a

  sensitive test for finding out the astigmatism.

d) Jackson cross cylinder test- confirms the power and axis of cylindrical lenses and is

mostly useful for refining the spectacle prescription.

      Treatment of Astigmatism includes prescribing appropriate cylindrical lens after

accurate refraction. Modalities include spectacle correction, hard contact lens and in

cases of higher astigmatism, toric lenses. Astigmatism nowadays is increasingly being

tackled surgically with procedures like Astigmatic keratotomy, Photo astigmatic

refractive keratotomy, Astigmatic epi-LASIK, Astigmatic LASIK and Astigmatic C-



                 Any opacity in the lens or its capsule, whether developmental or acquired,

   is termed a cataract. Cataract is caused by the degeneration and opacification of the lens

   fibres or deposition of other materials in their place.

                 Specific investigations include slit lamp examination for grading the

   cataract and when the fundus cannot be seen – macular function tests namely detection

   of projection of rays, Maddox rod test, entoptic phenomenon and two-point

   discrimination test and colour vision needs to be tested.

                 Cataract surgery or removal of the crystalline lens is performed if the lens

   is causing visual loss by virtue of opacification, subluxation or dislocation, defects in

   shape or any lens induced complications. The various strategies include:

 Intracapsular cataract extraction

 Conventional Extracapsular cataract extraction

 ECCE by small incision cataract surgery or

   Small incision manual nucleus fragmentation

 Lensectomy

 Phacoemulsification


                      In developing countries, manual small incision cataract surgery is

       becoming very popular because of its merits over conventional ECCE as well as

       Phacoemulsification. In this technique, ECCE with intraocular lens implantation is

       performed through a sutureless self-sealing valvular sclera corneal tunnel incision under

       local anesthesia preferably.

       Surgical steps include:

   1. Superior rectus (bridle) suture is passed to fix the eye in a downward gaze.

   2. Conjunctival flap and exposure of sclera. A small fornix based conjunctival flap is made

       with the help of sharp tipped scissors along the limbus from 10 to 2 o’clock positions.

       Conjunctiva and the Tenon’s capsule are dissected, separated from the underlying sclera

       and retracted to expose about 4mm strip of sclera along the entire incision length.

   3. Haemostasis is achieved by applying gentle and just adequate wet field cautery.

   4. Sclera- corneal tunnel incision. A self sealing sclero-corneal tunnel incision is made in

       manual SICS. It consists of the following components:

  i.   External sclera incision

 ii.   Sclera-corneal tunnel

iii.   internal corneal incision

    A Side port entry of about 1.5mm valvular corneal incision is made at 9 0’clock position.

       This helps in aspiration of the sub- incisional cortex and deepening the anterior chamber

       at the end of the surgery.

   Anterior capsulotomy

   Hydro dissection

   Nuclear management:

 i.   Prolapse of nucleus

ii.   Delivery of the nucleus by irrigating wire vectis method/ Blumenthal technique/

      phacosandwich technique/phacofracture technique/fishhook technique.

   Aspiration of cortex

   IOL implantation

   Removal of viscoelastic material

   Ensuring a sealed wound.

                              In many patients cataract co-exists with glaucoma. Glaucoma is

      a chronic, progressive optic neuropathy caused by a group of ocular conditions which

      lead to damage of the optic nerve with loss of visual function. The most common risk

      factor known is raised intraocular pressure. Specific investigations include tonometry to

      access the iop either digitally or by applanation tonometry, optic nerve head changes to

      be detected by direct and indirect ophthalmoscopy, gonioscopy to grade the degree of

      glaucoma and perimetry to access the visual field defects in relevant cases.

  Although, in adults, several surgical options like Peripheral iridectomy, Goniotomy,

  Trabeculotomy, Artificial drainage shunt operations and Cyclo- destructive procedures

  are available, filtering procedures like trabeculectomy is the most preferred.

          Trabeculectomy, first described by Carain in 1980, is the most frequently

   performed partial thickness filtering surgery till date.

   Mechanisms of filteration:

  i. A new channel fistula is created around the margins of sclera flap, through which

   aqueous flows from anterior chamber into the conjunctival space.

 ii. If the tissue is dissected posterior to the sclera spur, a cyclodialysis may be produced

   leading to increased uveoscleral outflow.

         Initial steps of anaesthesia, cleansing, draping, exposure of eyeball and fixation

   with superior bridle suture is done

         Conjunctival flap. A fornix based or limbal based conjunctival flap is fashioned

   and the underlying sclera is exposed. The Tenon’s capsule is cleared away using a

   Tooke’s knife and haemostasis is achieved using cautery.

         Sclera flap. A partial thickness limbal based sclera flap of 5mm x 5mm size is

   reflected down towards the cornea.

 Excision of trabecular tissue. A narrow strip of the exposed deeper sclera near the cornea

   containing the canal of Schlemm and the trabecular meshwork is excised.

 Peripheral iridectomy is performed at the 12 o’clock position with de Wecker’s scissors.

    Closure:     the sclera flap is replaced and 10-0 nylon sutures are applied. Then the

       conjunctival flap is reposited and sutured with two interrupted sutures or continuous


    Sub conjuctival injection of dexamethasone and gentamicin is given.

       The sclera flap can be tested for adequate flow resistance, before closing the

       conjunctival flap, by injecting balanced salt solution into the anterior via a paracentesis.


                             In the management of a patient with a cataract with coexisting

       glaucoma, the options for surgical correction include:

  i.   A cataract extraction alone

 ii.   Glaucoma filtering procedure alone, followed by cataract removal at a later stage

iii.   Combined cataract and glaucoma surgery as a one stage procedure.

                            As compared to cataract surgery alone, combined procedures have a

       greater risk of complications such as increased inflammation, hyphema, hypotony,

       shallow anterior chamber, and choroidal detachments, but they have an advantage of less

       early IOP rise. For these reasons the operating surgeon should consider each of the basic

       surgical options and select the approach that seems to be most appropriate for each




                    Between the two extremes i.e those patients with good glaucoma control

   and those with uncontrolled glaucoma which poses an immediate threat to vision, there

   is a third group of patients with borderline glaucoma status for whom combined

   procedure may be indicated. There is often a fine line of judgement involved in selecting

   these cases, although the following situations are some in which such an approach might

   be preferred.

a) Glaucoma under borderline control despite maximum tolerable medical therapy,

b) Adequate IOP control, but significant drug induced side effects

c) Adequate IOP control on well tolerated medical therapy, but advanced glaucomatous

   optic atrophy,

d) Uncontrolled glaucoma, but an urgent need to restore vision or when two operations are

   not feasible.

   The rationale for a combined procedure, as opposed to cataract surgery alone, in eyes

   with good IOP control but advanced damage, is the risk of a transient pressure rise in the

   early post operative period. Studies have shown that the early post operative pressure

   rise is significantly less after a combined procedure than after cataract extraction

   alone5, 6.

Modifications in the combined surgery:

                         A soft eye is necessary which can be achieved by a mercury

bag or oculo-compression or mercury bag or by digital pressure. After retrobulbar

injection of anesthesia, a superior rectus bridle suture is placed. A limbus or fornix based

conjunctival flap can be used. A lamellar scleral flap is incorporated into the 10mm

chord length incision. It is outlined in a square, trapezoidal or half moon shape with a

sharp knife. Grooves are made on both sides of the sclera flap along the posterior limbal

border to the desired extent of the corneoscleral incision. A two-planed incision in which

the entry incision is beveled is preferred and the anterior chamber is entered anterior to

the schwalbe’s line, at the proximal extension of the sclera flap.

                        An anterior capsulectomy is performed. An iridoplasty may be

required if the pupil dilates poorly. A rectangular trabeculectomy site is outlined with

four incisions, two parallel to and perpendicular to the limbus. The small rectangular

piece of deep sclera is excised. A punch can be inserted to cut a hole in the sclera and a

peripheral iridectomy is formed. The nucleus is expressed using the standard bimanual

technique and sutures are put to form a relatively closed eye. The centre suture is cut and

a PCIOL is inserted after the capsular bag is inflated with a viscoelastic material. The

incised iris is not usually sutured and the larger pupil permits evaluation of the retina

and the optic nerve. The scleral flap is loosely sutured and the conjunctival flap is closed

with absorbable or non absorbable sutures.


                Normally, the vertical corneal meridian is more steeply curved than the

horizontal meridian in with-the-rule and is corrected by a plus cylinder whose axis is at

90 degrees. While in against-the-rule astigmatism, the horizontal corneal meridian is

more steeply curved than the vertical meridian and is corrected by a plus cylinder whose

axis is at 180 degrees.

                In the recent times, post-operative astigmatism has given rise to a lot of

concern as it interferes with the final outcome of a well performed ocular surgery and

thereby delays the visual rehabilitation. There still exists considerable confusion and

difference in opinion regarding the pathophysiology of postoperative astigmatism

following SICS, Trabeculectomy and combined procedures due to the differing

techniques employed in the various studies undertaken. Post-operatively, patients can

develop either a with–the-rule astigmatism or against-the-rule astigmatism.


                  The size, architecture and location of the incision together influence the

post-operative astigmatism following a cataract extraction. The incision is more than a

port of access into the anterior chamber as it represents an important step of the

operation thereby affecting ocular integrity and corneal stability.7

                 Sato performed a posterior half incision the midpoint of which was

placed on the steeper meridian of the cornea in which the refractive power of the eye is

greatest8. The effectiveness of this procedure was maximal when the incision was made

tangential to the pupil. This was later corroborated by Corcostegui Moliner, who also

reported that the reduction of refraction in the meridian of greatest curvature is greater

the larger the amplitude of the keratotomy, the more tangential the incision is to the

cornea and the closer it is to the pupil9. The studies undertaken by N S Jaffe showed that

the smaller the amplitude of the incision, the less the effect there is on the horizontal

meridian. Incisions ending at or beyond the horizontal meridian tend to neutralize some

of the changes in the vertical meridian10, 11.

                             Small incisions are beneficial as they induce less corneal

distortion, promote more rapid wound healing and provide more control of the anterior

chamber during surgery12-14. The best incision for cataract surgery ensures no leakage

and has minimal influence on corneal shape. Drews found that 2.0 mm wounds had

essentially no effect on corneal astigmatism, showing almost no shift over 5 years12. In

their study in 60 patients, Beltrame et al. found a mean induced astigmatism of 0.7D

with 3.5mm incisions13. Steinert et al. found an induced astigmatism of 1D with 4mm

incisions and Naesser et al reported astigmatism of 0.6D averaged across 59eyes with 4

mm incisions14, 15.

                               The effect of location of the incision on the corneal

curvature is related to the delayed wound healing observed with anterior incisions.

Kohnen et al and barequet et al in their respective studies have both reported a

statistically significant reduction in astigmatism in a temporal approach when compared

to a nasal incision16, 17. A similar study was undertaken by Nikhil.S.G where he similarily

reported that induced astigmatism was lower in groups where temporal and

superotemporal incisions were made when compared to the group with a superior


                     Using non-absorbable sutures material (nylon) leads to with-the-rule

 astigmatism at 6 weeks whereas using absorbable or removable suture (chromic catgut

 or silk) leads to against-the-rule astigmatism. In an effort to reduce the progression of

 this against-the-rule astigmatism usually seen following extracapsular cataract

 extraction, 10-0 monofilament polypropylene sutures and 10-0 monofilament polyester

 sutures were introduced as they tend to remain in the eye longer before degrading19.

 However with the advent of Phacoemulsification, the beveled nature of the incision

 ensures a sutureless closure of th incision. In his study Masket found that the sutureless

 incisions skip the with-the-rule phase and at once demonstrate against-the-rule

 astigmatism even on the first post-operative day20. Thus, sutures tend to cause with-the-

 rule astigmatism and both sutured as well as un-sutured incisions move towards against-

 the-rule astigmatism over time.


                       Trabeculectomy affects the corneal curvature but the post-

operative astigmatism following trabeculectomy does not follow a similar trend as of post

cataract astigmatism. In majority of patients undergoing this procedure, the vertical

corneal radius of curvature is reduced with a trend towards with-the-rule astigmatism.

The horizontal radius of curvature is increased and thus there is a steepening in the

vertical meridian. In the various studies undertaken the above trend was marked in the

first 3 months of early postoperative period and decreased by the third post-operative


                          Hugkulstone was one of the first to undertake a study

regarding astigmatism post trabeculectomy3. He found similar changes of reduction in

vertical corneal radius of curvature following trabeculectomy. Rosen et al found that 5

out of 8 eyes developed 1.5 – 2.0D of steepening in the vertical meridian following

trabeculectomy21. Cunliffe IA et al discovered that the change in vertical corneal

curvature after trabeculectomy is consistent with the with-the-rule change in corneal

astigmatism22. Similar studies conducted by several

others23-27 show that trabeculectomy causes certain with-the-rule astigmatism which in

most of the cases may decrease as time passes by, though a statistically insignificant

small number of patients developed a superior corneal flattening.

                            Various explanations have been put forward to explain this

effect of trabeculectomy on corneal curvatures. It may be related to the surgically

produced gap in trabeculectomy is overlaid by a partial thickness scleral flap which is

capable of spreading any support from the sutures inserted into it over the whole of

wound gape. The more posterior placement of the incision and the use of cautery

producing a scleral contraction in the meridian of surgery may also explain this trend of

with-the-rule astigmatism following trabeculectomy.


                                       Studies on induced corneal astigmatism following

combined cataract and trabeculectomy are few and comparison among the studies

limited due to the different surgical techniques employed in these studies. Earlier studies

have demonstrated a tendency to the development of against-the-rule astigmatism

following a combined surgery, with an average induced cylinder of about 2D against-
the-rule astigmatism            . Hong et al reported a shift of astigmatism at the vertical

meridian from +2.17 D to -1.72D over 12 months after a combined operation26.

Choplin, in his study compared the amount of surgically induced astigmatism between

eyes undergoing combined cataract- filteration surgery and cataract surgery alone and

concluded that about 1.00D of the induced against-the-rule astigmatism was due to the

filtering procedure itself31.

                         Hence, it is quite evident that very few studies have been

undertaken to determine the post operative astigmatism induced by a combined

procedure and the exact nature and explanation of the deviation remains to be



                The objective of this study is to compare the post-operative Astigmatism

following combined Cataract extraction with Trabeculectomy to the post-operative

Astigmatism following Cataract extraction alone.



Patients (maintaining inclusion & exclusion criteria) attending the ophthalmology

outpatient department of the Yenepoya Medical College & Hospital.


                     This is a prospective study of the comparison of the postoperative

astigmatism following cataract surgery to combined cataract and trabeculectomy surgery

during a period of one and half years.

       Study Type: Comparative Study.

       Duration of Study: One and half years.

       Sample Size: Forty patients (selected using purposive sampling technique),

twenty of whom will undergo Small Incision Cataract Surgery with PCIOL implantation

in one eye will be included in the study. Another twenty patients will undergo a

combined Small Incision Cataract Surgery with PCIOL Implantation combined with

Trabeculectomy. Data will be collected in accordance with the clinical Proforma.

These forty patients will be categorized into two age matched groups as follows:

Group A will comprise of 20 patients who will undergo Small Incision Cataract Surgery

         with PCIOL Implantation alone.

Group B will comprise of 20 patients who will undergo Small Incision Cataract Surgery

        with PCIOL Implantation combined with Trabeculectomy.


      a.   visual acuity tests

      b. Streak retinoscopy

      c. Slit lamp examination

      d. Pachymetry

      e. Corneal reflex

      f. Keratometry

      g. Corneal topography (in relevant cases)


          All cases of senile cataract without any other ocular disorder.

          All cases of glaucoma with co-existing cataract with normal cornea.


          Grossly altered corneal topography

          Any history of previous ocular surgery

          Post operative complications

          Any preceeding eye disease other than cataract or glaucoma


                 Data will be collected in accordance with the inclusion-exclusion criteria

and analysed by t-tests between the two groups- A and B. The sample size being 40 patients.

                         CONSENT FORM.

Patients Information                     Relatives Information

Name:                                    Name:

Sex:          Age:        Year:          Sex:              Age:           Year:

Registration No.                         Address:


Operation:                               Relationship with the patient:

I ……………………………………… the undersigned GIVE CONSENT for

timely investigations and for co-operating to be a part of the study undertaken

by Dr. RAJNA.

The precise nature of the study and the investigations has been explained to me /

my bystander in my own language and I have understood the procedure and give

my consent willingly.

Patient/ relative:

Signature/ L.H.T.I:




          S. No               HOSPITAL NUMBER                DATE

           NAME                      A/S             OCCUPATION

S.No COMPLAINTS                              RE   Duration      LE   Duration

1.     Diplopia.

2.     Glare.

3.     Photophobia.

4.     Watering of eye.

5.     Blurred vision.

6.     Pain.

7.     Prolonged use of any topical drugs.

8.     Redness.

9.     Headache.

10.    Coloured halos.

11.    Any previous ocular surgeries?

12.    Any trauma?

13.    Others

      Past history:

 Personal history:

 Tobacco/ Alcohol/ Smoking/ Computer use/ others

 Ophthalmic Examination

 1. Vision                                     RE        LE



Near Vision

 2. Gaze:

       Ocular movements:

 3. Ocular examination:

                                    RE              LE

Lids and Adnexa




Anterior chamber




4. Vision:

5. Anterior segment:

                    RE         LE

6. Slit- lamp examination:

7. Refraction:

                         R.E   L.E

8. Keratometry:



9. I.O.P:



         Diurnal variation:

            RE                LE

10. Direct ophthalmoscopy:

11. Syringing:

12. Pachymetry:

13. Treatment:

14. Surgery underwent:

15. Date of surgery:

   16. Any post-operative complications:

   17. Post-operative medications:

   18. Follow - up:

7.3 Does the study require any investigations or interventions to be conducted on

patients or other humans or animals? If so please describe briefly.

              The study will involve non invasive investigations on humans

Ethical clearance: Has ethical clearance been obtained from your institution in

case of 7.3?

                     Yes

8. List of References:

1. Peskinoff S , Pascolini D, Etya’ale D, Kour I, Pararajasegaram R, Pokharel GP,

   Mariotti SP. Global data on visual impairment in the year 2002. Bull World Health

   Organisation 2004; 82(11):844-5.

2. Mehmooda Ashai, Anheta Ahmed, Mohd.Ahsan, Ali I. The effect of trabeculectomy

   on corneal astigmatism. JK Practitioner 2006; 13(1):27-29.

3. Charles E Hugkulstone. Changes in keratometry following trabeculectomy. BJO

   1991; 75:217-218.

4. Duke-Elder S. System of Ophthalmology, Vol 5, Ophthalmic optics and refraction,

   St. Louis, 1970, CV Mosby.

5. Krupin, T, Feitl, ME, Bishop, KI. Postoperative intraocular pressure rise in open-

   angle glaucoma patients after cataract or combined cataract filteration surgery.

   Ophthalmology 1989; 96:579.

6. Murchison, JF, Jr, Shields, MB. An evaluation of three surgical approaches for

   coexisting cataract and glaucoma. Ophthalmic Surg 1989; 20:393.

7. Heller MD and others. Wound healing after cataract extraction and position of the

   vitreous in aphakic eyes as studied postmortem. Trans Am Ophthalmol Soc 1971;


8. Sato T. Posterior half-incision of cornea for astigmatism. Am J Ophthalmol 1953;


9. Corcostegui Moliner A. Surgical treatment of astigmatism. Arch Soc Oftal Hisp Am

   1956; 16:750-760.

10. Jaffe NS: Cataract surgery and its complications. ed 1, St.Louis, 1972, CV Mosby.

11. Jaffe NS, Clayman HM. The pathophysiology of corneal astigmatism after cataract

   extraction. Trans Am Acad Ophthalmol Otolaryngol 1975; 79:OP615-630.

12. Drews RC. Five year study of astigmatic stability after cataract surgery with

   intraocular lens implantation: Comparison of wound sizes. J Cataract Refract Surg.

   200; 26:250-3.

13. Beltrame G, Salvetat ML, Chizzolini M, Driussi G. Corneal topographic changes

   induced by different oblique cataract incisions. J Cataract Refract Surg 2001; 27:720-


14. Steinart RF, Brint SF, White SM, Fine IH. Astigmatism after small incision cataract

   surgery: a prospective, randomized, multicenter comparison of 4.0 and 6.5mm

   incisions. Ophthalmology 1991; 98:417-423.

15. Optical Laboratories Association. American National Standard for Ophthalmics-

   Intraocular Lenses. Merrifield VA: Optical Laboratories Association; 1994.

16. Kohnen S, Neuber R, Kohnen T. Effect of temporal and nasal unsutured limbal tunnel

   incisions on induced astigmatism after phacoemulsification. J Cataract Refract Surg.

   2002; 28:821-825.

17. Barequet IS, Yu E, Vitale S, Cassard S, Azar DT, Stark WJ.Astigmatism outcomes of

   horizontal temporal versus nasal clear corneal incision cataract surgery. J Cataract

   Refract Surg. 2004; 30:418-423.

18. Nikhil S Gokhale, Sourabh Sawhney. Reduction in astigmatism in manual small

   incision cataract surgery through change of incision site. Indian Journal of

   Ophthalmology 2005; 5(5):201-203.

19. Cravy TV: Long-term corneal astigmatism related to selected elastic, monofilament,

   nonabsorbable sutures. J Cataract Refract Surg.1989; 15:61-69.

20. Masket S. One year post-operative astigmatic comparison of sutured and unsutured

   4.0mm sclera pocket incisions. J Cataract Refract Surg. 1993; 19:453-456.

21. Rosen WJ, Mannis MJ, Brandt JD. The effect of trabeculectomy on corneal

   topography. Ophthalmic surg. 1992; 23(6):395-8.

22. Cunliffe IA, Dapling RB, West J, Longstaff S. A prospective study examining the

   changes in factors that affect visual acuity following trabeculectomy. Eye 1992; 6(Pt


23. Claridge KJ, Galbraith JK, Karmel V, Bates AK. The effect of trabeculectomy on

   refraction, keratometry and corneal topography. Eye 1995; 9(Pt 3):292-8.

24. Liu H, Peng D, Chen J. Corneal astigmatism following trabeculectomy. Zhonghua

   Yan Ke Za Zhi 1996; 32(5):355-8.

25. Diotze PJ, Oram O, Kohnen T, Feldam RM, Koch DD, Gross RL. Visual function

   following trabeculectomy: effect on corneal topography and contrast sensitivity.

   J Glaucoma 1997; 6(2):99-103.

26. Hong YJ, Choe CM, Lee YG, Chung HS, Kim HK. The effect of mitomycin-C on

   post-operative corneal astigmatism in trabeculectomhy and a triple procedure.

   Ophthalmic Surg Lasers 1998; 29(6):484-9.

27. Vernon SA, Zambarakji HJ, Potgieter F, Evans J, Chell PB. Topographic and

   keratometric astigmatism upto 1 year following small flap trabeculectomy

   ( microtrabeculectomy). Br J Ophthalmol 1999; 83(7):779-82.

28. Simmons ST, Litoff D, Nichols DA, Sherwood MB, Spaeth GL. Extracapsular

   cataract extraction and posterior chamber intraocular lens implantation combined

   with trabeculectomy in patients with glaucoma. Am J Ophthalmol 1987; 104:465-70.

29. Mc Cartney DL, Memmen JE, Stark WJ, Quigley HA, Maumeneee AE, Gottsch JD,

   Bernitsky DA, Wong SK. The efficacy and safety of combined trabeculectomy,

   cataract extraction and intraocular lens implantation. Ophthalmol 1988; 95:754-63.

30. Johnson D. Extracapsular cataract extraction, intraocular lens implantation and

   trabeculectomy: the combined procedure. Int Ophthalmol Clin 1990; 20:498-503.

31. Choplin NT, Monroe JF. Surgically- induced astigmatism in combined ECCE with

   filtering procedures compared to ECCE alone. Ophthalmic Surg 1992; 23:81-84.

9.Signature of candidate:

10.Remarks of the guide :        An important study to know if Trabeculectomy
                                 combined with cataract surgery affects the corneal
                                 curvature differently from Cataract surgery alone.

11.0 Name of the Guide:          Dr. NEELAM PUTHRAN.
(in block letters)
11.1 Designation of the Guide:   Professor,
                                 Dept of Ophthalmology,
                                 Yenepoya Medical College,
                                 Deralakatte, Mangalore.
11.2 signature:

11.3 Co-guide(if any):           Nil.

11.4 signature:                  -

11.5 Head of the department:     Dr. A.B.KAKADE.

11.6 signature:

12.0 Principal:                  Dr. R. N. SUJEER.

12.1 Remarks of the principal:

12.2 Signature:


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