Ret by keralaguest


									 Retinoscopy
     o Dynamic retinoscopy: clinician moves retinoscope further away or closer to
        patient to find neutrality
     o Static streak retinoscopy: determines the refractive error of the eye relative to
        the point of fixation
            Patient fixated at optical infinity (viewing a distance target) with
               accommodation relaxed
                    Accommodation relaxed by either:
                   1. Patient with no accommodation (presbyope)
                   2. Cycloplegia
                   3. “Fogging”
     o Retinoscope has 2 modes
            Plano mirror---light beam is divergent
                    Apparent source is behind the retinoscope aperture
            Concave mirror---light beam is convergent
                    Forms a virtual image in front of the retinoscope
                    Motion opposite that found with plano mirror
     o Purpose is to find the far point of the eye
            Moderate to high myopia
                    Far point between clinician and patient
            Low myopia (lower than clinician’s working distance)
                    Far point is behind clinician
            Emmetropia
                    Far point is at infinity
            Hyperopia
                    Far point is behind patient
            Astigmatism has 2 far points (one for each principal meridian)
     o With motion: reflex moves in same direction as you are moving the light bean
            Far point either behind retinoscope (myopia less than your working
               distance) or behind the patient’s retina (hyperopia) or at infinity
            Add PLUS lenses (“down with”)
     o Against motion: reflex moves in opposite direction from the direction you are
        moving the light beam
            Far point is between your retinoscope and the patient’s eye (moderate-
               high myopia)
            Add MINUS lenses (“up against”)
     o Neutrality: when the far point is at the retinoscope aperture (not “with” or
            Range of neutrality ~0.50 D
                    Upper end of neutrality is called “high neutral” (most PLUS
                    Lower end is called “low neutral” (most MINUS endpoint)
          Occurs initially (no lenses added) only with myopia exactly equal to your
           working distance
o   The clinician uses the retinoscope and lenses of a known amount to create a
    myopic eye in which the far point coincides with the retinoscope aperture
o   Retinoscope light should be moderate intensity
        Too bright will constrict pupil, cause glare, and too much infrared may
           damage the eye
        Too dim and you cannot see reflex well
o   The reflex is an image of illuminated section of fundus focused in the far point
    plane, and the retinoscopist’s visual system projects the image onto the pupil of
    the patient
o   Reflex characteristics
        Direction
                With: myopia less than your working distance, hyperopia,
                Against: moderate to high myopia
        Brightness
                At neutrality, most of the light that exits the patient’s pupil will be
                   focused at the retinoscope aperture= bright reflex
                If the far point is some distance away from the retinoscope
                   aperture, only a small amount of light enters the retinoscope= dim
                Note: for highly ametropic eyes, little light enters the aperture
                   making the reflex very dim
                Dim reflex may also be the result of small pupils (hyperopes,
                   elderly), highly pigmented RPE and media opacification
                       o To increase brightness: increases the intensity of
                          retinoscope, decrease working distance, dilate pupil, or
                          move to concave to concentrate light on a smaller area of
                          the fundus
                Reflex is brightest at neutrality
        Speed
                Speed is related to working distance, vertex distance, and residual
                       o If working and vertex distances are constant, speed is
                          determined by the eye’s residual ametropia
                More than 3.00 D away, it is only half as fast as the speed of light
                   on the iris
                Reflex speed is about the same as the light on the iris at 1.50 D
                   from neutrality (at 0.50 D 3X speed, 0.25 D 6X speed, 0.12
                   D 12X speed of the incident beam)
                At neutrality, the speed is infinite
                Note: close to neutrality small changes in working distance can
                   make a big difference in motion seen (worse for shorter WD)
                Closer to neutrality, faster reflex
        Width
               Reflex is about the width of the pupil at + 3.00 D from neutrality
               Coming from with:
                      o Plus lenses are added to move neutrality reflex gets
                      o Reflex is skinniest at hyperopic point where the far point
                        coincides with the apparent light source of the retinoscope
                        and the blur circle is smallest
                      o After skinniest point, more plus is added and reflex gets
                      o At neutrality, reflex gets so wide it fills the pupil
               Coming from against:
                      o Minus lenses are added to reach neutrality  streak stays
                        wider than pupil
                      o Fills the pupil at neutrality
               Further from neutrality, wider reflex
       Definition
               Coming from with:
                      o Reflex will be most sharp when the far point of the patient’s
                        eye coincides with the apparent source
                             Same place reflex is thinnest
                      o Sharpness decreases as more plus is added and neutrality
                        is reached
               Coming from against:
                      o Definition of the reflex becomes sharper until neutrality is
                      o A very sharp reflex is not seen because the far point never
                        coincides with the apparent source before neutrality is
               Closer to neutrality, sharper reflex
       Alignment
               Retinoscope beam aligned with axis of cylinder straight line
               Retinoscope beam rotated away from axis skewed line
                      o If you are not lined up, the motion will not be directly with or
o Minus cylinder phoropter
       Find neutrality for the principal meridian with the least minus or most plus
         first (least myopia or most hyperopia)
               Both against motion- scope against closest to neutrality
               Both with motion- scope with farthest from neutrality
               One with and one against- scope the with
         (Axis of cylinder is perpendicular to the principal power meridian)
o Scissors motion
       Refractive status of the eye is different in one part of the pupil than
        Causes of scissors:
              Large pupils with spherical aberration and coma (myopes, light
                irides, young dilated all have big pupils)
                    o SA and coma make the eye’s refractive power greater in
                        the periphery of the pupil (more myopic at the edge)
              Keratoconus
              Irregular astigmatism
       Neutralize the central reflex (ignore the peripheral)
       May need to make room brighter to constrict pupils
o False neutrality
       Due to the sleeve pushed into concave somewhat and light is focused on
         the entrance pupil
              Retroillumination—the light source at the pupil illuminates the
                whole fundus
              No reflex motion
o Control of accommodation
       Use a lighted, distance, target bi-ocularly (20/400 E with red/green)
              Red/green filter reduces the brightness of the target so there are
                fewer reflections from the lenses in front of the patient’s eyes
       Sudden changes in reflex and pupil constriction, patient accommodating
       If accommodation fluctuates a lot, suspect latent hyperopia,
         psuedomyopia, or other accommodative problem
       Fogging
              Add plus lenses to fixating eye until it shows against motion
                    o Will be overplused by at least your working distance
              Patient will not accommodate because it will not make the target
                any clearer
              After you neutralize the right eye, move directly over to examine
                left **Right will be fogged with your working distance**
              If fogging does not work, do a wet retinoscopy (cycloplegic)
                    o Cycloplegia may eliminate the normal tonic accommodation
                        and the wet ret may be +0.50D or +0.75D more
              Fogging may not work for latent hyperopia, psuedomyopia, or
                other accommodative problems
                    o Latent hyperopes initially fogged have accommodative
                        spasm, but will continue to relax during retinoscopy
o Clinical technique
       Prepare distance target
       Seat patient and adjust the patient’s chair
       Adjust PD and level the phoropter
       Reduce room illumination
       Explain to the patient where to look
              If patient cannot view the target with the fixating eye b/c the eye
                being examined is strongly dominant, move farther temporally or
                rotate phoropter slightly or shift target off onto the wall
                If patient has a large-angle strabismus or large phoria and the
                 non-fixating eye drifts in/out from primary position, 1) change
                 position of gaze of the fixating eye to bring the examined eye
                 closer to the midline, 2) move to a position that will line you up
                 with the pupil of the deviated eye being examined or 3) some
       Sit temporal to the patient’s eye you are neutralizing
       Holding retinoscope with right hand, look through the aperture with your
         right eye and change lens power with left hand (vice versa)
       Fog patient
              If significant against motion is present in the two principal
                 meridians of the left eye, the eye is already fogged greater than
                 you working distance
              If one (or both meridians) is at neutrality or has with motion, add
                 plus lenses until significant against motion is seen for both
       Note: if specular reflections from the cornea or on the lenses are
         interfering with your ability to see the reflex, either 1) tilt lenses in front of
         patient or 2) move a little less or a little more temporal
       Find the endpoints and correct for your working distance
              Remove from both meridians is using a lens cross with spherical
                 trial lenses or lens bars
              If you use phoropter or trial frame with cylindrical lenses, only take
                 working distance out of sphere *DO NOT CHANGE THE
       Check monocular VAs
o Potential errors
       Variable working distance
       Irregular astigmatism
       Scissors
       False neutrality
       Obliquity of observation
              More temporal the aperture is to the patient’s line of sigh, the more
                 against the rule minus cylinder is induced
                     o With 5° of obliquity 0.12 DC x 090 is induced
                     o With 10° of obliquity 0.37 DC x 090 is induced
                     o With 15° of obliquity 0.75 DC x 090 is induced
              If your head blocks the view of the examined eye but the fixating
                 eye can see the target, the obliquity is less than 3°
o Retinoscopy has the tendency to be more hyperopic than refraction by +0.25D
  to +0.50D in young eyes but the tendency becomes more minus with age

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