This document summarizes key concepts related to strabismus and eye movement examination. It defines terms like strabismus, visual axis, anatomical axis, orthophoria and describes tests to evaluate eye alignment and movement including: - Hirschberg test to measure strabismus angle - Cover-uncover test and alternate cover test to detect heterotropia and heterophoria - Prism bar cover test for measuring strabismus angle - Synoptophore for grading binocular vision - Maddox rod test for detecting horizontal and vertical phorias - Extraocular muscle actions and innervations are also summarized.

1. Anuraag Singh

2.  Strabismus- misalignment of the visual axis.
 Visual axis - line of vision extending from the
point of fixation to the fovea
 Anatomical axis - is a line passing from the
posterior pole through the centre of the cornea .
 Orthophoria -perfect alignment of the visual axes

3.  It is the angle formed between visual axis and the
anatomical axis
 As the fovea lies just temporal to the anatomical
axis, a light shown into the cornea will cause reflex
(on the visual axis) just nasal to the center of the
cornea in both eyes (+ve angle kappa = 5°).

4.  In high myopia the, the fovea lies nasal to the
optical axis. So, the corneal reflex lies temporal to
the center of the cornea simulating esotropia.
 Negative angle kappa (myopia) leads to pseudo-
esotropia.
 Large positive angle kappa (hypermetropia) leads
to pseudo-exotropia.

5.  Heterophoria - (latent squint) tendency of the eyes to
deviate. Ocular alignment maintained with effort.
 Heterotropia - (manifest squint) which is present at
all times
 Esophoria- latent squint inwards turning of the eyes
 Esotropia- manifest squint inwards turning of the
eyes
 Exophoria- latent squint outwards turning of the
eyes
 Exotropia- manifest squint outwards turning of the
eyes
 Hyperphoria/hypertropia- latent/manifest squint
upwards turning of eyes
 Hypophoria/hypertropia- latent/manifest squint
downwards turning of eyes

7.  Horizontal muscles :-
 Medial rectus- Its sole action in the primary
position is adduction.
- occulomotor nerve supply
 Lateral rectus- Its sole action in the primary
position is abduction
-abducens nerve supply

8.  Vertical muscles
 Superior rectus- Primary action elevation
(secondary actions are adduction and intorsion.
- Oculomotor nerve supply
 Inferior rectus - The primary action is depression ;
secondary actions are adduction and extortion.
- Oculomotor nerve supply

9.  Superior oblique - The primary action is intorsion
- secondary actions are depression and
abduction.
- oculomotor nerve supply
 Inferior oblique - The primary action is extorsion
- secondary action are elevation and abduction .
- oculomotor nerve supply

10.  Listing plane is an imaginary coronal plane
passing through the centre of rotation of the
globe. The globe rotates on the X,Y and Z axes of
Fick which intersect in Listing plane .
 The globe rotates left and right on the vertical Z
axis.
 The globe moves up and down on the horizontal X
axis.
 Torsional movements (wheel rotations) occur on
the Y (sagittal ) axis which traverses the globe form
front to back (similar to the anatomical axis of the
eye )
 Intorsion occurs when the superior limbus rotates
nasally and extorsion on temporal rotation .

12.  Ductions
 Monocular movements around the axes of Fick.
 They consist of adduction, abduction elevation,
depression, intorsion and extorsion .
 They are tested by occluding the fellow eye and
asking the patient to follow a target in each
direction of gaze.

13.  Versions
 Binocular, simultaneous, conjugate movements
( in the same directon ) .

14.  VERGENCES
 Vergences are binocular, simultaneous
disconjugate or disjunctive movements.
 Convergence is simultaneous adduction.
 Divergence is outwards movement from a
convergent position.

15.  Positions of gaze:-
 Six Cardinal positions of gaze are those in which
one muscle in each eye has to move the eye into
that position as follows:
 Dextroversion
 Levoversion
 Dextroelevation
 Levoelevation
 Dextrodepression
 Levodepression
 Nine Diagnostic position of gaze are those in which
deviations are measured. They consists of the six
cardinal postions ,the primary position, elevation
and depression .

17.  Antagonist - muscles of the same eye moving the
eye in opposite direction (medial and lateral rectus)
 Synergists- muscles of the same eye moving it in
the same direction (superior rectus and inferior
oblique causing elevation)
 Yoke muscles- muscles of both eyes moving the
eyes in same direction; medial rectus of both eyes
 Sherrington’s law- increase in innervation to one
muscle causes decreased innervation to its
antagonist (medial and lateral rectus)
 Hering’s law- equal innervation flows to yoke
muscles in eye movement ( medial rectus of both
eyes)

19.  Age of onset of deviation
 Is the deviation constant or intermittent?
 Is the deviation present for distance, near or both?
 Is it unilateral or alternating?
 Is it present only when the patient is inattentive or
fatigued?
 Is it associated with trauma or physical stress?
 Old photographs
 Birth history
 Is there a family history of strabismus?.
 Are there any other medical problems?
 Is there a history of toxin or medication exposure?

20. 1.Objective methods
2.Subjective methods
1.Objective methods:-
 Hirschberg corneal reflex test
 Krimsky’s test
 Bruckner test
 Cover uncover test
 Alternate cover test
 Prism bar cover test
 Synoptophore

21. 2.Subjective methods:-
 Maddox rod test
 Maddox wing test
 Maddox tangent
 Double maddox rod
 Maddox double prism
 Hess screen
 Red green glass test
 Diplopia field

22.  Used as initial screening test for strabismus.
 Amount of deviation: note location of corneal light
reflex 1 mm = 7° or 15Δ
Corneal reflex at border Corneal reflex at limbus
of pupil = 15° = 45°

24.  This test is used to centralize the corneal reflection
in squinting eye as compared to the reflex in fixing
eye.
 Results are expressed in prism diopter (PD).
 Convenient test for quick evaluation of the angle
of strabismus, especially in the abnormal fixation
of the squint eye.

25.  Performed by using direct ophthalmoscope to
obtain a red reflex simultaneously in both eyes.
 Deviated eye will have a lighter and brighter reflex
than the fixing eye.
 Bruckner test positive for left eye esotropia

26. 1.Cover test:-
 To detect a heterotropia
Procedure:-
1.The patient fixates a straight ahead target
2.If a right deviation is suspected , the examiner
covers the fixing left eye
Note any movement of the right eye to take up
fixation

27.  No movement indicates orthotropia
 Adduction of right eye indicates right exotropria
 Abduction of right eye indicates right esotropia
 Down movement indicate right hypertropia
 Upward movement indicate right hypotropia
 Test is repeated on opposite eye

29.  Detects heterophoria
Procedure:-
Patient fixates a straight ahead distant target
Examiner covers the right eye and after 2-3 seconds
removes the cover
No movement indicates orthophoria
 If the right eye had deviated while under cover ,a
re-fixation movement is observed on being
unconvered.

30.  Aduction ( nasal recovery) of right eye indicates
exophoria and abduction ( temporal recovery )
indicates esophoria.
 Upward or downward movement indicates a
vertical phoria.
 The test is repeated for the opposite eye

31.  Dissociation test
 Reveals total deviation when fusion is suspended
Procedure:-
Right eye is covered for several seconds
Occluder is quickly shifted to opposite eye for 2
seconds ,then back and forth several times
Note the recovery as the eyes return to their pre-
dissociated state

32.  A patient with well compensated heterophoria
will have straight eyes before and after the
test.
 A patient with poor control may
decompensate to a manifest deviation

33.  The prism cover test measures the angle of
deviation
 It combines alternate cover test with prisms
Procedure:-
The alternate cover test is performed first
Prism of increasing strength placed in front of one
eye with base opposite the direction of deviation
Alternate cover test is performed continously as
stronger prisms are used

34. Amplitude of refixation gradually decreases
End point reached when no movement is seen
To ensure maximum angle is found , prism strength
is increased until movement is observed in opposite
direction
Then reduced again to find neutral value
Angle of deviation equals the strength of the prism

36.  A translucent occluder is used.
 Covering both eyes with translucent occluders
permits a quick preliminary determination of
whether an esotropia is of refractive –
accommodative or non-accommodative origin.

37.  Consists of
 Chinrest
 Forehead rest
 Two cylindrical tubes with mirrored right
angled bend and +6.50 D lens in each
eyepiece.
 This optically sets the testing distance as
equivalent to 6 m.

39.  Tubes are placed horizontally and supported by
a column
 Distance between the tubes can be adjusted -
correspond accurately to the pt’s IPD.
 The axis of tube is in line with the center of
rotation of the eyes.
 Adjustments for vertical separation of targets
and cyclorotational adjustments
 Illumination system
 Increase or decrease stimulus luminance

40.  Deviation is measured by moving the arms of the
synaptophore into the position that images of the
target fall on the respective foveal areas.
 Horizontal deviations are compensated for by
moving the synaptophore arms, vertical deviations
by elevating or depressing the synaptophore
pictures.
 It can measure horizontal,vertical and torsional
misalignments simultaneously.
 It can be used for grading the binocular vision

41. 1.First grade ( Simultaneous perception )
 Tested by introducing two dissimilar but not
mutually anatagonistic pictures , such as lion and a
cage.

42. 2.Second grade ( fusion )
 Ability of two eyes to produce a composite picture
from two similar images, each of which is
incomplete in one small different detail

43. 3.Third Grade ( stereopsis )
 Ability to obtain an impression of depth
 Superimposition of two pictures of same object
taken from slightly different angles

44.  It is based on the principle of dissociation
 Maddox Rod consists of a series of plano
cylinder lenses about 3 mm in diameter,
mounted in a trial frame lens.
 A spot of light viewed through the
Maddox Rod appears as an elongated
streak.
 The Maddox Rod is often colored usually
red.

45.  Used to find out presence of heterophoria or
heterotropia
 Easy for patient to understand
 Easy to administer
 Very useful for vertical deviations.

46.  Reduce room illumination.
 Maddox Rod is placed in front of one eye
 Measuring horizontal deviations maddox Rod axes
are placed horizontal which produces vertical
streak
 Measuring vertical deviations maddox Rod axes are
placed vertical which produces horizontal streak
 Patient initially views with both eyes open

49.  Maddox Rod is placed horizontally (vertical streak)
in front of right eye
 With strabismics, the Maddox Rod is best placed
over the fixating eye
 Ensure that patient can see white light and streak
simultaneously
 Ask if the streak is to the right or to the left of the
light

51.  Same procedure is followed except maddox rod is
placed with its axes vertically producing horizontal
streak of light
 If the horizontal streak of light is above the
fixation light it indicates presence of hypo
deviation
 If the horizontal streak of light is below the
fixation light it indicates presence of hyper
deviation

52.  It is based on the principle of dissociation
 Instead of maddox rod a red glass is used
 Tangent scale is used

53.  Procedue
1.Patient is asked to fix the white light
2.Through the red glass light looks like a red spot
3.In orthophorics red spot overlaps white light
4.In deviation red spot can be either on left or right
of white light.

54.  For amount of heterophoria in near
fixation
 A vertical arrow is presented to one eye
and a horizontal tangent scale to the
other to give the measurement of the
horizontal phoria .
 A horizontal arrow and vertical scale are
used to measure the vertical imbalance.
 Scales are mounted at the fixed viewing
distance of 1/3m.

56.  Quantitative determination of cyclodeviation
 Red and white maddox rods are placed in the trial
frame. Red before RE and white before LE.
 Direction of glass rods is aligned with the 90° mark
of trial frame

58.  Screen contains a tangent pattern ( 2D projection
of a spherical surface ) printed on dark grey
background.
 Red lights ( can be individually illuminated )
indicate the cardinal positions of gaze
 Each square represents 50 of ocular rotation.
Procedure :-
1.Patient seated 50cm from screen wearing red-
green goggles ( red in front of right ) and holds a
green pointer.
2.Examiner illuminates each point in turn which is
used as point of fixation.seen only with right eye (
becomes fixating eye )

59. 3.Patient asked to superimpose their green light on
red light , so plotting the relative position of left
eye.all points are plotted.
4.The goggles are then reversed and procedure
repeated.
5.The relative positions are marked by the examiner
on a Hess chart and connected with straight lines.
 In orthophoria two lights more or less superimpose
in all nine positions of gaze.

61.  Suppression is an acquired cerebral function used
by the patient to avoid confusion and diplopia.
 Patient may not be aware of suppression
 Suppression scotoma is present in tropias. It
prevents diplopia.
 Tests for suppression :-
1.Worth four dot test
2.Prism 4 PD base out test
3.Red glass test
4.Synoptophore

62.  It consists:-
 Self illuminating panel of
1.Two green
2.One red
3.One white
 Generally done at 6m
 Patient wears a red green glass :; red in front of
right eye.
 When the patient looks through green glass the
patient can see only green spots and white spot
looks light green.
 While looking through red glass he can only see
the red spot and white spot looks pink.

63.  When a normal patient looks with both eyes open,
he sees two green, one red and one mixture of red
and green.
 In case of left supression ,the patient will see two
red lights.
 In case of right supression ;sees three green lights.
 If the patient sees five lights in presence of ocular
deviation, patient has diplopia and normal retinal
correspondence.

64.  A patient with deviation and normal vision should
experience diplopia unless he is ignorig or
suppressing it.
 Procedure:-
Patient fixes a white light
A red glass put in front of deviated eye
Patient become aware of second image as a red light
 If there is deep suppression only white light will be
visible

66.  Special slides used to detect suppression
 Depth of suppression can be measured by
altering the illumination of the slides.

67.  Normal retinal correspondence :- when
anatomically corresponding areas of two eyes
correspond to each other.

68.  In abnormal retinal correspondence :- an
extra foveal area of squinting eye and fovea
of fixing eye have a common visual direction.
 It’s a crude method of retaining binocular
vision in squint.
 More developed in microtropia

69. 1.Bagolini striated glasses
2.Worth four dot test
3.After image test
4.Synoptophore
Bagolini striated glasses:-
 Bagolini glasses – plane
- on one surface multiple parallel
lines etched
Procedure:-
 Glasses mounted o trialframe
 Done at 33cm or 6m

70.  Spot of white light seen
 Both eyes are kept open
 Lens in right eye set at 45o
axis
 Lens in left eye set at 135o axis

71.  Patient sees only one slanting line – other is
suppressed
 Lines cross each other (perfect cross), eyes are
straight and have central fixation - NRC
 Deviation + perfect X - ARC

72.  Shining vertical light thrown on fovea of right eye
 Similar (intensity and size ) horizontal light thrown
on fovea of left eye
 Light thrown for 20 seconds
 Patient looks at fixation point
Interpretation:-
1.Perfect cross with central gap – central fixation
with NRC

73. 2.Vertical after image shifted to right – ARC with
right exotropia with central fixation
3.Vertical after image shifted to left – ARC with right
esotropia with central fixation

74. 1.Uniocular or binocular
 Uniocular diplopia disappear on closing affected
eye
 Binocular diplopia disappear on closing either eye
2.False and true images
 False image – formed in deviated eye at a point
other than the macula.
- blurred as compared to true image
- may be separated from true image
- distance may vary at different
positions of gaze and head
- may be tilted
-

75.  Crossed diplopia – false image projected across the
midline
 False image formed in direction opposite to
displacement.
 Seen in Paralysis of adductors- MR,SR,IR
 Uncrossed diplopia – false image do not cross
midline
 Seen in paralysis of abductors- LR,SO,IO

76.  Qualitative tests for Stereopsis:
 Lang’s 2 pencil test
 Synoptophore
 Quantitative tests for Stereopsis:
 Random Dot test
 Titmus Fly Test
 TNO Test
 Lang’s Stereo Test

77.  TNO random dot test consist of seven plates of
randomly paired red and green dots which are
viewed with red-green spectacles.
 Within each plate the dots of one colour forming
the target shape are displaced horizontally in
relation to their paired dots of other colour.

78.  Frisby stereotest consist of three transparent
plastic plates of varying thickness.
 On the surface of ach plate are printed four
squares of small randomly distributed shapes
 One of the squares contains a hidden circle,in
which the shapes are printed on the reverse of the
plate.

79.  Lang stereo test doesn’t require special spectacles
 Targets are seen alternately by each eye through
the built in cylindrical lens
 Displacement of the dots creates disparity
 Can often be used in very young children who may
reach out to touch the pictures.

80.  Titmus test consist of 3D polaroid vectograph
 Two plates in form of booklet viewed through
Polaroid spectacles
 On the right is a Large fly
 On the left is a series of circles an animals

81. 1.Fly is a test of gross stereopsis, useful for
young children
 Fly should appear stand out from the page
,child is encouraged to pick up the tip of one
of its wings between finger and thumb.
 In absence of gross stereopsis fly will appear
as ordinary flat photograph.
 In book is inverted the targets will appear to
be behind the plane of the page

82. 2.Circles comprise a graded series which tests fine
depth perception.
 Each of the nine squares contains four circles
 One of the circle in each square has a degree of
diparity and will appear forward of the plane in
presence of normal stereopsis
3.The Animals consist of three rows of animals , one
of which appear forward of the plane of refrence.