College of Medicine and Health Science,

Department of Optometry

Presentation On Clinical Evaluation of Strabismus

Moderator:- Mr. Ayanaw Tsega (BSc, MSc).
By:- Bekalu G.
 Clinical Evaluation
Presentation
 poor VA

 Impaired depth perception

 Reduced sensitivity to contrast

 Reduced sensitivity to motion

 Deviated eyes

 Parental concern

 Family history of strabismus

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History and symptoms
Detailed history of the patient and the family including:-
 Pregnancy Hx

 Birth Hx
 Did its onset coincide with trauma or illness?
 Is the deviation constant or intermittent?

 Is it present for distance or near vision or both?

 Is it unilateral or alternating?
 Is it present only when the patient is inattentive or fatigue?

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  Does the child close 1 eye?
 Is the deviation associated with double vision or eye strain?
 Age of onset of the problem

 General health
 Early treatments taken like medical, optical or surgical
 Family history of strabismus

 Inspection of previous photographs may be useful for the

documentation of strabismus or an AHP.

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Distance and near VA

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 use age appropriate chart.

 pinhole may be used to estimate the best visual acuity

potential.
 Identify the type of test used
 The reliable test that the child can perform should be used.
 Log MAR testing is becoming more popular.
 Avoidance movements can be demonstrated when the good
eye is occluded.
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 Assessment of Ocular Alignment

A. Cover Tests
 cover-uncover test

 Eye movement capability, image formation and perception,

foveal fixation in each eye, attention, and cooperation are all

necessities for cover testing.

 most important test for detecting the presence of manifest
strabismus and for differentiating a heterophoria from a
heterotropia
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 Alternate cover test
 measures the total deviation, regardless of whether it is latent or
manifest

 simultaneous prism and cover test

 helpful in determining the actual heterotropia when both eyes are
uncovered (heterotropia alone).
 performed by covering the fixating eye and at the same time the
prism is placed in front of the deviating eye.
 Has special application in patients with monofixation syndrome
 All can be done both at distance and near
 Note the type, size and quality of recovery movement 8
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 Tests for monofixation syndrome
 Vectograph projections of Snellen letters

– Snellen letters are viewed through polarized analyzers or goggles equipped

with liquid crystal shutters in such a way that some letters are seen with only
the right eye, some with only the left eye, and some with both eyes.
– Patients with monofixation syndrome delete letters that are imaged only in
the non fixating eye.
 Stereo acuity tests

– demonstrate 200- 3000 sec of arc but Fine stereopsis (better than 67 sec
of arc) is present only in patients with bifixation

 Bagolini striated lenses

 4∆ base-out test 10
4∆ base-out test

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 B. Light Reflex Tests

 Hirschberg method
 1 mm decenteration = 7 degree or 15 prism
 Krimsky test
 uses reflections produced on both corneas by a penlight
and is ideally used at near fixation
 The original method involved placing prisms in front of
the deviating eye.
 More common modifications today involve holding
prisms before the fixating eye or split between the 2 eyes
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The Hirschberg and Krimsky methods can be inaccurate
their use is often limited to patients who are uncooperative or
have vision that is too poor

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Bruckner test
 direct ophthalmoscope is used to obtain a red reflex
simultaneously in both eyes.
 the deviated eye will have a lighter and brighter reflex than
the fixating eye.
 the test detects, but does not measure, the deviation.
 It also identifies opacities in the visual axis and moderate
to sever anisometropia.
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Major amblyoscope
 method uses separate target illumination, which can be
moved to center the corneal light reflection.
 The amount of deviation is then read directly from the
scale of the amblyoscope

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 C. Dissimilar Image Tests

Maddox rod
 a series of parallel cylinders that convert a point source of light into a

line image.

 Heterophorias and heterotropias can not be differentiated.

 Can test horizontal, vertical and cyclodeviations

 To measure the amount of deviation, the examiner holds prisms of

different powers until the line superimposes the point source.

 It is not a satisfactory test for quantitating horizontal deviations,

because accommodative convergence cannot be controlled. 17

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Double Maddox rod
 used to determine cyclodeviations.

 The degrees of deviation and the direction (incyclo or excyelo) can be

determined by the angle of rotation that causes the line images to appear

horizontal and parallel.

 Traditionally, a red Maddox rod was placed before the right eye and a

white Maddox rod before the left eye.

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Red glass test
 a red glass is placed in front of the fixating eye.

 can be performed both at distance and at near.

 5 or 10 prism base-up placed in front of the deviated eye can be used

to move the image out of the suppression scotoma, causing the patient
to experience diplopia.

 With NRC, the white image will be localized correctly: the white
image is seen below and to the right of the left image

 With ARC, the white image will be localized incorrectly: it is seen

directly below the image
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 If the measured separation between the 2 images equals the
previously determined deviation, the patient has NRC
 If the patient sees the 2 lights superimposed so that they appear
pinkish despite a measurable esotropia or exotropia, HARC present.
 If the patient sees 2 lights (with uncrossed diplopia in esotropia and
with crossed diplopia in exotropia), but the separation between the 2
images is found to be less than the previously determined deviation,
UHARC present.
 prisms are used to eliminate the horizontal or vertical diplopia and
the amount of deviation is recorded. 21
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 D. Dissimilar Target Tests

Lancaster red-green test

 uses red-green goggles, a red-slit projector, a green-slit projector,

and a screen ruled into squares.

 The patient's head is held steady; by convention, the test is begun

with the red filter in front of the right eye.

 The examiner projects a red slit onto the screen, and the patient is

asked to place the green slit so that it appears to coincide with the

red slit.

 The relative positions of the 2 streaks are then recorded . 23

 The test is repeated for the diagnostic positions of gaze and
the goggles are then reversed so that the deviation with the
fellow eye fixating can be recorded.
Major amblyoscope test

• uses dissimilar targets that the patient is asked to

superimpose.
• If the patient has normal retinal correspondence, the
horizontal, vertical, and torsional deviations can be read
directly from the calibrated scale of the amblyoscope
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 Assessment of Eye Movements
 Ocular rotations at 9 diagnostic positions of gaze

 Asses version movements first then if versions are not full,

duction movements should be tested for each eye separately.

 Limitations of movement into these positions and
asymmetry of excursion of the 2 eyes should be noted.

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 A simple numeric system may be employed using 0 to
denote full movement, and −1 to −4 to denote increasing
degrees of underaction
 And from +1 to +4for overacting muscle.
 Head must keep straight

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Look for:  corneal reflex

 both eyes move smoothly and  fatigue on testing

follow target  pain/tension in face
 there is a corresponding lid  Px should report:
movement accompanying the
 Diplopia/pain on movement
vertical eye movements
 Monocular vs. Binocular
 there is no underaction or
motility
overaction of the movement of
one eye in any direction of gaze
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 changes in lid position
 Red and Green goggles

 Red filter in front of one eye, green in front of the other

 Px views pen torch, if sees diplopia, one light is red, the other green
 Eye which sees outermost of a diplopic image in cardinal position =
eye with paretic muscle

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 Special tests
Motor Tests
 Forced ductions
 Active force generation
 Differential intraocular pressure test
 Saccadic velocity

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3- step test
 To identify the paretic cyclovertically acting muscle

 It is not always diagnostic and can be misleading, especially in patients in whom

more than 1 muscle is paralyzed, in patients who undergone strabismus surgery, and

in the presence of restrictions or DVD

Step 1
 determine which eye is hypertropic by using the cover uncover test

 narrows the number of possible underacting muscles from 8 to 4. in Figure 6-9, the

right eye has been found to be hypertropic. This means that the paralysis will be

found in either the depressors of the right eye (RIR, RSO) or the elevators of the left

eye (LIO, LSR). Draw an oval around these 2 muscle groups. 31

Step2
 Determine whether the vertical deviation is greater in right gaze or in

left gaze. In the example, the deviation is larger in left gaze.

 Draw an oval around the 4 vertically acting muscles that are used in

left gaze. At the end of step 2, the 2 remaining possible muscles (1 in

each eye) are both intortors or extortors and both superior or inferior

muscles (l rectus and 1 oblique).

 Note that, the increased left gaze deviation eliminates 2 inferior

muscles and implicates 2 superior muscles.

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Step 3
 Known as the Bielschowsky head tilt test, involves tilting the head to

the right and then to the left during distance fixation

 Head tilt to the right stimulates intorsion of the right eye (RSR, RSO) and
extorsion of the left eye (LIR, LIO). Head tilt to the left stimulates extorsion
of the right eye (RIR, RIO) and intorsion of the left eye (LSR, LSO).

 when the head is tilted to the right, in order to maintain fixation, the right
eye must intort and the left eye must extort. Because the right superior
oblique is weak, the vertical action of the right superior rectus is unopposed.

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 Contraction of this muscle in an attempt to incycloduct the eye results
in an upward movement of the right eye, thus increasing the vertical
deviation.

 Because the oblique muscles are minor elevators and depressors, the
difference in vertical alignment of the eyes will be smaller during
head-tilt testing when there is a paresis of the vertical rectus muscles

as compared to the oblique muscles.

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Accommodative convergence/accommodation ratio
 It is defined as the amount of convergence measured in
prism diopters per unit (diopter) change in accommodation.
 Used to change the spherical prescription
 Clinically measured using either
 Gradient method

 Heterophoria/calculated method

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Tests for sensory adaptation and binocularity
 Worth 4 dot test
 Bagolini striated lenses
 Stereo acuity testing

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Worth 4-Dot Testing

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Bagolini striated glasses
 This is a test for detecting BSV, ARC or suppression.
 Each lens has fine striations which convert a point source of light into
a line image
 The glasses are usually placed at 135 degree in front of the right eye
and at 45 degree in front of the left eye.
 The advantages of the Bagolini glasses are that they afford the most
lifelike testing conditions and permit the examiner to perform cover
testing during the examination.

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Stereo acuity Testing
 assesses the use of the 2 eyes for depth perception.
 Stereopsis occurs when the 2 retinal images slightly disparate because
of the normally different views provided by the horizontal separation
of the 2 eyes, are cortically integrated.

 Can be Random dot tests or Contour -based tests

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 Stereopsis can also be measured at distance using the AO Project-O-
Chart with Vectograph slide or the Smart System II
 TNO and frisby are highly important for those child's who reject
wearing spectacles

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Cycloplegic Refraction
 Important test in the evaluation of any patient with complaints
pertinent to binocular vision and ocular motility.
 Prescription depends on the amount and type of refractive error,
type of cycloplegic drug used and age of the patient

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 References
BCSC
Duane's

Kanski 7th edition

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THANK U!

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