2. ā«Strabismus is misalignment of eyes.
ā«GOALS OF STRABISMUS EVALUATION
ā¢ To find the etiology of strabismus
ā¢ To assess the binocular status
ā¢ To measure the amount of deviation
ā¢ To diagnose amblyopia,
ā¢ To define a plan of management.
ā«
3. ā«A strabismus patient may be examined in the
following order:
ā¢ Eliciting a detailed history
ā¢ Visual acuity assessment
ā¢ Cycloplegic refraction
ā¢ Fundus examination
ā¢ Sensory tests
ā¢ Measurement of deviation
ā¢ Ocular motility examination
ā¢ Special tests for specific diagnosis
5. HISTORY
ā«Presenting complaintsshould be recorded in the
patientāswords.
ā«The age of onset and duration of squint is very
important for the prognosis regarding attainmentand
maintenanceof binocularsinglevision.
ā«Whether thedeviation is intermittentorconstant,
unilateral or alternating has to beasked
ā«History of treatment taken in the past like spectacles,
patching, previous surgery (for strabismus ,glaucoma
implant, retinal detachment, etc) should be noted.
6. ā«Family historyshould be taken forpresence of
hereditary formsof strabismus.
ā«historyof significant head posture, confirmed byold
photographs, may indicate good binocularpotential.
ā«Antenatal and perinatal history is important forany
squintappearing since birth.
ā« A patientwith recentonsetof squint may presentwith
diplopia, past-pointing, abnormal eye movementsand
headache.
7. EXAMINATION
ā«General Inspection of the Patient
Observationof thedegree and direction of squint.
āPresence of wide nasal bridge with increased
interpupillarydistanceand epicanthal foldswhich may
be thecauseof pseudoesotropia, needs to be noted.
ā Observationof facial asymmetry.
ā Presence of an abnormal head posture is noted
8. ā« Upward ordownward slanting of palpebral fissures.
ā Ptosis.
ā Any lid/conjunctival scarring.
āPupillary reactions are abnormal in patients with
sensory deviation due to diseases of retina and the
optic nerve
ā« Assessment of Visual Acuity : In children above 5 years
various Snellenās charts can be used
Media and fundus examination:
ā« It is important to evaluate the eye for any organic
abnormality that could be causing visual loss and
secondaryor sensory strabismus.
9. ā«It is the starting point forevaluation forstrabismus.
ā«A refractiveerrorcould be the primary ora
contributing causeof the strabismus.
ā« Correction of the refractive error is paramount to the
managementof strabismus.
ā« It is performed at the end of strabismusexamination
and preferably under full cycloplegia forchildren.
10.
11.
12.
13. ā«Assessment of Vision in Nystagmus
near acuity targets visible with binocular
viewing must be ascertained Before assessing
monocular vision in nystagmus patients
ā«When assessing monocular vision, an occluder
placed in front of one eye worsens the nystagmus
and leads to a decline in visual acuity.
ā« This decline can be avoided by high plus lenses by
fogging or neutral density filters
14. ā«Examination of squintcan beconsidered in two
aspects:
a. Examination of sensory status
b. Examination of motorstatus
15. ā« Sensory testing is an essential part of strabismus
evaluation. Itcomprises theassessmentof the binocular
status of theeyes
ā« different sensory adaptations that can take place in
response toclinical situations thatdisrupt binocularvision
are
ā« 1. Visually mature (occurring after thevisual system is
mature)
2. Visually immature (occurring during visual development
)
ā«
16. ā«Visually Mature:sensoryadaptationsoccurafter the
development of bifoveal fusion, when the visual
system is mature.
ā«Theseareassociated with normal retinal
correspondence.
ā« Visual neural development is said to mature by
around 9 to 10 years of age.
ā«at this point there is not enough cortical plasticity
foradaptations such as cortical suppressionand ARC
17. ā«Diplopia: The patientswith diplopia fixatewith one
fovea, and suppress the foveaof thedeviated eye.
ā«Thediplopic imagescome from the perifoveal retinaof
thedeviated eye.
ā«The foveal image from the fixing eye is perceived as
being located directly in frontof the patient.
ā«while the perifoveal retinal image from thedeviated
eye projects to itscorresponding visual field.
ā«
18. ā«Exotropia causes the image to fall temporal to the
fovea, which projects to the nasal field producing
ācrossed diplopiaā
ā«Esotropiacauses the image to fall on the nasal retina,
which projects temporallyand causes āuncrossed
diplopia ā
ā«
19. ā«Confusion: Instead of diplopia, strabismicpatients
with confusion perceive two different images
superimposed on topof each other.
ā«Confusion iscaused by the simultaneous perceptionof
twodifferent images from the two foveae thatare
pointing todifferentobjects
ā«It is rarely seen clinically.
20. ā«Rivalry: is a condition where a patient with normal
binocularvision is presented with different images to
corresponding retinal pointsof each eye.
ā«Instead of seeing twodifferent images superimposed
on each other (confusion)
ā«the subject perceives patchydropoutof each image
where the images binocularlyoverlap
21.
22. ā«The following sensoryadaptationsoccurwhen the
binocularity is disrupted during the first fewyears of
life, usually before 8 to 10 yearsof age.
ā«Monofixation and suppression: Small angle
strabismus (<10 PD), or mild to moderateunilateral
retinal image blur, in young children and infants
causes
-a central suppressionscotomaof thedeviated or
blurred eye,
- central fixation of the preferred eye,
- but peripheral fusion is maintained
23. ā«It refers to the ability of the sensory system to
appreciate the perceived direction of the foveaand
otherretinal elements in each eye relative to theother.
ā«The twoeyes havecorresponding retinal elements that
haveacommonvisual direction
ā«The two foveae represent the highestdegree of
correspondence
ā«Abnormal retinal correspondence (ARC) is a
sensory adaptationof the immaturesensoryvisual
system toan abnormal motorposition of theeye.
24. ā«Worthās Four Dot Test: The patientwearsa red glass
in front of right eye and a green glass in front of left
eye.
ā« He then viewsa boxwith four lights; one red, two
green and onewhite
25. ā«If all four lightsare seen, normal fusion is present.
ā¢If all four lightsare seen in the presenceof a manifest
deviation, ARC is present.
ā¢ If twored lightsare seen, leftsuppression is present.
ā¢If threegreen lightsare seen, right suppression is
present.
ā¢ If twored and threegreen lightsare seen, diplopia is
present.
ā¢If the red and green lightsalternate, alternating
suppression
is present.
26.
27. ā«Bagoliniās Striated Glasses: Each lens is covered
with fine striations which convert a point source of
light intoa line, similar to the Maddox rod.
ā« The two lenses are placed at 45 degrees and 135
degrees in frontof each eyeand the patient fixatesa
punctate light sourceplaced at 6 meteraway.
ā«
28.
29. ā«This is the leastdissociativeof all diplopia tests.
Itpermitsdeterminationof whetherthe patient is:
ā¢ Fusing
ā¢ Suppressing oneeye
ā¢ Suppressing centrallyonly
ā¢ The typeof retinal correspondence present.
30. ā«After Image Test: This testdemonstrates thevisual
direction of the fovea.
ā«One fovea is stimulated byavertical bright flash
of light and the felloweye is stimulated bya horizontal
flash of light.
ā«Thevertical flash of light is harder tosuppressand
should beapplied to thedeviating eye.
ā« The patient then draws the relativepositionsof the
after images.
31. ā«Synoptophore: This is an instrument for
- assessing strabismus,
-Quantifying binocularsinglevision (BSV)
-DetectsARC and suppression
32. ā«Grades of binocular vision: Binocularvision isgraded
on the basisof Synoptophore.
ā«Firstgradeā(simultaneous macularperception) is
tested by introducing twodissimilar but not mutually
antagonistic pictures.
ā«one picture is smaller than the other so that the
smallerpicture is seen by the foveaof oneeyeand the
larger picture is seen by the parafoveal area of the
othereye.
33. ā«Second gradeā(fusion) is the ability of the two eyes to
produceacompositepicture from twosimilarpictures
each of which is incomplete in one small different
detail.
ā«Third gradeā(stereopsis) is the ability to obtain an
impression of depth by the superimposition of two
picturesof the sameobjectwhich has been taken from
slightlydifferentangles ā¦
34.
35. ā«These tests useone fixation target that is seen by both
eyes. Here wedisrupt fusion byobscuring or
eliminating peripheral fusion clues, or providing
different images toeach eye .
.Diplopiacharting test
ā¢ Maddox rod (Mostdissociating)
ā¢ Worth fourdot test
ā¢ Red filtertest
ā¢ Bagoliniās lenses (leastdissociating)
36. ā« Diplopia test: Plotting of diplopia fields is indicated in patients
complaining of confusion ordoublevision.
ā« The patient is asked to wear red-green charting goggles; red in
frontof the righteyeand green in frontof the lefteye.
ā« The patient is made to sit with his head straight in a semi dark
room and is shown a fine linear light fromadistanceof 4 feet.
ā« The light is moved from primaryposition intoall of othereight
directions of gaze.
ā« For each direction, the patient is asked to comment on the
position, brightness, separation between the red and green
imagesand the relativeangleof one imageto theother.
37.
38.
39. ā« The Maddox rod consists of a series of parallel glass
cylinders of higher power (usually red color) set
together in a metallicdisk.
ā« The Maddox rod produces a linear imageof a point light,
when viewed through the rod the line image is formed
perpendicularto theaxis of thecylinders.
ā« The rod is placed in front of the righteye. Thisdissociates
the two eyes because the red streak seen by the right eye
cannot be fused with the unaltered white light seen with
the left eye.
ā« does not differentiate between tropiaand phoria.
ā«
40.
41. ā«Maddox Wing Test: Maddox wing is an instrument by
which the amount of heterophoria for near (1/3rd m)
can be measured subjectively.
ā« The instrument is constructed in such away that the
right eye sees only a white vertical arrow and a red
horizontal arrow,
ā« whereas the lefteye sees the horizontal and vertical
rowsof numbersonly
42.
43. ā«The horizontal deviation is measured by asking the
patient towardswhich numberthewhitearrow points.
ā«Thevertical deviation is measured byasking the
patients regarding the number the red arrow
intersects.
ā«The amount of cyclophoria is measured by asking the
patient to movethe red arrow so that it is parallel with
the horizontal rowof numbers.
44. ā«Itutilizes the principleof Heringās lawof equal
innervation.
ā«The test is performed with each eye fixating in turn.
The patient wears the red and green dissociating
glasseswith the red glass overright eye.
ā« sits at 50 cm from an illuminated screen on which
each red targetcan be lit up in turn and its position
indicated by the patientusing a lineargreen light.
ā«In orthophoria, the two lights are more or less
superimposed in all nine positions of gaze. The
relativepositionsareconnected with straight lines.
ā«
45.
46. ā«Leeās Screen: The apparatus consists of two opalescent
glass screens at right angles to each other, bisected by a
twosided plane mirrorwhich dissociates the twoeyes.
ā«
47. ā«Interpretation of Hess/Lee's Screen Test
ā¢ The twochartsare compared.
ā¢The smallerchart indicates theeyewith the paretic
muscle.
ā¢The largerchart indicates theeyewith theoveracting
muscle.
ā¢The smallerchartshows itsgreatest restriction in the
main direction of action of the paretic muscle.
ā¢The largerchartwill shows its expansion in the main
directionof action of theyoke muscle.
50. ā«Head posture has threecomponents:
a. Chin elevationordepression (vertical)
b. Face turn to the right or leftside (horizontal)
c. Head tilt to the right or leftshoulder (torsional).
ā«These three components at three different joints
between the head and the neck correct for the motility
disturbances in the threedimensions
ā«The patientchooses the head posture
where theoculardeviation is least, theocular
alignment is maximumand where the imagescan be
fused.
51.
52. ā« Light Reflex Tests
Hirschberg test:A pen torch is shone into the eyes from
armās length and the patient is asked to fixate upon the
light.
ā«If theeyes are deviated, the light reflex fallson
different locations instead of thecenter.
ā«1 mm deviation = 7 degrees deviation =14 pd deviation
ā«
53.
54. ā«Krimsky test: It is a modification of the Hirschberg
test.
ā«A prism is placed in front of one eye with the apex
towards thedeviation, a pen light is then thrown into
both eyes and the patient is asked to fixate on the
accommodativetarget.
ā«The prism is then increased or decreased until
the reflex becomes symmetricallycentered in the
pupil.
ā«
55. ā«Bruckner test: This test is performed by using the
directophthalmoscope toobtaina red ref lex from
botheyes simultaneously.
ā«In patientswith strabismus, the testshowsasymmetric
reflexes with the brighter reflex coming from the
deviated eye.
ā«
56. ā«based on the patientāsability to fixate,
ā«both eyes should havecentral fixation.
ā«They allow the examiner to differentiate tropia from
phoria,
ā«Assess the degree of control of deviation, and note
fixation preference and strength of fixation of each
eye.
57. ā«Gold standard objective method
ā«Use: todifferentiate
-between phoriaand trophia
-detectpseudostrabismus
-differentiate concomitant from incomitant squint
ļ done for both near (33cm) and distance (6 meter)
ā«Consistof 3 parts
1)covertest -confirms tropia
2)uncovertest ā todiagnose phoria
3)alternatecovertest āmeasure total deviation
58. Ask pt tofixate on targetand look forany deviation
Deviationvisible ,eg:LE exo
Do COVER TEST,By
covering fixing eye,i.e RE
withoccluder
Deviated LE
moves inward
to take
fixation,so RE
under occluder
also moves due
to herrings law.
CONFIRMS
EXOTROPHIA
No movement,
Indicate
pseudosquint
Deviation notvisible
Do COVER TEST
If no movement of
uncovered eyeļ no tropia
But fusion is broken ,socovered eye moves
to position of least resistance.now do
UNCOVER TEST
61. ā«This test is done todissociate binocular fusion
in order todetermine the full deviation, including any
latentphoria.
ā«Alternately each eye is occluded and refixation
movementof uncovered eye to midline isobserved.
ā«Noshift in thealternatecovertest indicates
orthophoria.
ā«A refixation shift to indicates thatstrabismus is
present, eithera tropia, phoria.
62. ā«This testdetermines theamountof prism necessary to
neutralize the full deviation including any latent
phoria, by quantitating the shift associated with
alternatecovertesting.
ā«A prism is placed in frontof thedeviating eye
with theapex towards thedeviation.
ā«Alternate cover testing is then performed with the
prism in place, the prism is changed (either increased
ordecreased) depending on the refixation shift.
63. ā«Simultaneous prism cover test: It is used to measure
the tropiacomponentof the monofixation syndrome
withoutdissociating the phoria.
ā«therefore it is used in patientswith small angle
strabismus.
ā«A prism and occluder is presented
simultaneously in frontof eithereye
and this process is repeated until
there is no shift of the deviated eye
when the fixing eye is covered
64. ā« When measuring patients with restrictiveor paralytic
deviations the primary and secondarydeviation should be
considered.
ā« In accordance with Heringās law, thedeviation is larger
when theeyewith limited duction is fixing (secondary
deviation) than when the āgood eyeā fixes (primary
deviation).
ā« While measuring adeviation with prisms, theeyewithout
the prism is considered the fixing eyeand theeyewith the
prism is the non-fixing eye, irrespective of presence of
amblyopia.
ā« This is because theeyewithout the prism mustcome to the
primary position to take up fixation.
65. ā« Ductions : Monoocular movementsand are examined
with oneeyeoccluded,
-abduction
-elevation
-intortion
-adduction
-depression
-extortion
ā«Versions : are binocular ,simultatneous eye
movements In the samedirection ,i.econjugate
movements
-Dextroversion
-Dextroelevation
-Dextrodepression
-Sursumduction
-Levoversion
-Levoelevation
-Levodepression
-Deorsumduction
66. ā« Both horizontal and vertical ductions arequantified with
agraded 0 to minus 4 scale,
ā« with minusone limitation meaning slight limitationand
minus four limitation meaning severe limitation
ā« Evaluation of versions include eye movements through
all 9 cardinal gaze positions. Abnormal versions can be
noted on a scale of + 4 through 0 to ā 4, with 0 indicating
normal movement,
ā« + 4 indicating maximumoveraction, while ā 4 indicates
severe underaction.
ā« The rest of thegrades fall in between.
67.
68. - Binocular , simultaneous movements in opp direction
- i.e disgugate movements
-Vergenceamplitudesare tested in three planes:
1. Horizontal: Convergenceand divergence
2. Vertical: Sursumvergenceand deosumvergence
3. Torsional:Incyclovergenceand excyclovergence.
- Measurementcan either be donewith prismsor the
synoptophore
69. ā«Near point of convergence: The simplest way to
measure convergence is to bring a point drawn on
papercloserto theeyes, till the point becomesdouble.
ā«This in the nearpointof convergence. The pointat
which it becomes blurred is the near point of
accommodation
ā«Normally, the nearpointof convergence is 8 to 10 cm.
70. ā«Convergenceand divergence for near (33 cm) and
distance (6 m) can be measured with the helpof a
prism barorrotary prisms.
ā«Using base-outprisms, theconvergence
amplitudescan be measured
ā«using base-in prisms, thedivergenceamplitudesare
measured.
