This document provides information about strabismus and binocular single vision. It begins by defining key terms like strabismus, extraocular muscles, eye positions and movements. It then discusses tests and evaluations for strabismus, including visual acuity, ocular motility, versions, vergences and more. It also covers topics like abnormal retinal correspondence, horopter, Panum's fusional area, binocular convergence and monocular cues for depth perception. The document provides an overview of important concepts regarding strabismus and binocular vision.

1. Strabismus and
the Binocular Single Vision

2. The information provided within this lecture is for educational and
scientific purposes only and it should not be construed as
commercial advice.
Author thanks all of our teachers, fellow ophthalmologists,
publishers, sponsors, and all manufacturers for their works those
all being cited in this handout.
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2

3. Strabismus
•
•
•
•
•
•
Squint
Misalignment of extra ocular muscle
Misalignment of eye position
Misalignment of eye movement
Disorder in fusion
Disorder visual function  Binocular single
vision (BSV)

4. Position of gaze
• Primary position
– Straight ahead
• Secondary position
– Straight up, straight down
– Right gaze, left gaze
• Tertiary position  Four oblique position
– Up and right, up and left
– Down and right, down and left
• Cardinal position
4

5. Extra ocular muscle (EOM)
• Agonist
– Primary muscle moving the eye in a GIVEN direction
• Synergist
–
–
–
–
–
Muscle in the same eye
As the agonist
That can act with agonist
Produce a GIVEN movement
E.g : Superior rectus with Inferior oblique  elevate the eye
• Antagonist
– Muscle in the same eye as the agonist
– That can act with in the direction opposite
– E.g : Medial rectus and lateral rectus
5

6. Cardinal position and Yoke muscles
RSR
LIO
Right Gaze
LSR
RIO
RLR
LMR
LLR
RMR
RIR
LSO
LIR
RSO
Left Gaze
6

7. Basic
• Yoke muscle
– Two muscle (one in each eye)
– Are Prime mover of their respective eyes
– In GIVEN position gaze
– E.g : right gaze  RLR and LMR simultaneously innervated
and contracted  to be “yoked” together
7

8. Basic
• Sherrington’s law for reciprocal innervation
– Increased innervation and contraction of GIVEN EOM 
– Accompanied by reciprocal decrease of innervation and
contraction of its antagonist EOM
8

9. Basic
• Hering’s law of motor correspondence
– The state  equal and simultaneous innervation
flow to Yoke muscle
– Concerned with the desired direction of the gaze
9

10. Monocular eye movements
A- elevation
D- adduction
B- depression
E–extortion
C- abduction
F- intortion

11. EOM : Functions
Muscle
Primary
Secondary
Lateral rectus
Abduction
None
Medial rectus
Adduction
None
Superior rectus
Elevation
Adduction
Intorsion
Inferior rectus
Depression
Adduction
Extorsion
Superior oblique
Intorsion
Depression
Abduction
Inferior oblique
Extorsion
Elevation
Abduction
11

12. Eye movement
• Versions
– Eyes move in the same direction
• Vergences  Disconjugate binocular eye movement
–
–
–
–
–
Convergence
Divergence
Incyclovergence
Excyclovergence
Vertical vergence
12

13. Classification of strabismus
A. Pseudostrabismus (false or
apparent squint).
B. True strabismus:
1. Latent squint (heterophoria)
2. Manifest squint (heterotropia)
- non-paralytic (concomitant)
- paralytic (non-concomitant)

14. Variation of deviation
With gaze position or fixating eye
• Comitant (Concomitant)
– Deviation doesn’t vary in size with direction of gaze or
fixating eye
• Incomitant (Noncomitant)
– Deviation varies in size with direction of gaze or fixating
eye
– Most  paralytic or restrictive
– In acquired condition  may indicate neurologic or orbital
problems or diseases
14

15. Pseudo-strabismus
• In young infants,
strabismus must be
differentiated from the
more common pseudostrabismus
• Pseudo-esotropia as a
result of a broad bridge of
the nose. This is not a
real eye crossing

16. Pseudo-deviations
Pseudo-esotropia
Epicanthic folds
• Short interpupillary distance
• Negative angle
kappa
•
Pseudo-exotropia
Wide interpupillary
distance
• Positive angle kappa
•

17. In high myopia the, the fovea lies nasal to the optical axis. So, the
corneal reflex lies temporal to the center of the cornea  Negative
angle kappa .
Large negative angle kappa (myopia) leads to pseudo-esotropia.
Large positive angle kappa (hypermetropia) leads to pseudoexotropia.

18. (Brief) Classification of squint
• Latent (Heterophoria)
– Esophoria
– Exophoria
– Vertical ‘phoria
– Fully compensated
– Poorly compensated

19. (Brief) Classification of squint
• Manifest (Heterotropia)
– Esotropia (convergent)
– Exotropia (divergent)
– Vertical
– Unilateral or alternating
– Constant or intermittent (in Primary position, or in
certain positions of gaze)
– Accommodative

20. Assessment of squint
•
•
•
•
•
•
Visual Acuity
Cover Test
Ocular Movements
Convergence
Fusion/Stereopsis?
Measurement of angle (prisms)

21. Visual aquity
• Recognition acuity : Lea symbols, HOTV, Snellen Chart
• Detection acuity : Stycar Ball test
• Resolution acuity : Lea Paddles

22. Sensory evaluation
• Simultaneous macular perception
• Worth four dot test
• Stereopsis

23. Tests for sensory anomalies
Worth four-dot test
a - Prior to use of glasses
b - Normal
c - Left suppression/amblyopia
d - Right suppression/amblyopia
e - Diplopia
Bagolini striated glasses
a - Normal or ARC
b- Diplopia
c - Suppression
d - Small suppression scotoma

24. • Qualitative tests
for Stereopsis:
– Lang’s 2 pencil
test
– Synoptophore
• Quantitative tests
for Stereopsis:
– Random dot test
– TNO Test
– Lang’s stereo test

25. Tests for stereopsis
Titmus
•
•
Polaroid spectacles
Figures seen in 3-D
TNO random dot test
•
•
Lang
Frisby
•
•
No spectacles
‘Hidden’ circle seen
Red-green spectacles
‘Hidden’ shapes seen
•
•
No spectacles
Shapes seen

26. Motor evaluation
• Extra ocular muscles
• Cover test
• Corneal reflex test – Hirschberg
Krimsky
Bruckner
• Dissimilar image test – Maddox rod

27. Evaluation of motility
• Two principle methods of evaluating ocular
motility are:
1. Observation of ocular ductions, which are the
actual monocular movements of the eye.
2. Observation of binocular ocular alignment,
using cover/uncover and alternate cover testing.

28. Cover test: Exotropia

29. Cover test: Esotropia

30. Cover uncover test: Exophoria

31. Cover uncover test: Esophoria

32. Cover test detects heterotropia
Uncover test detects heterophoria
Alternate cover test detects total deviation

33. Prism cover test measures total deviation

34. Motility tests
Tests versions and ductions
Grades under/overaction
Left inferior oblique overaction
Left lateral rectus underaction

35. Hirschberg test

36. Krimsky test

37. Modified Krimsky test
• Asymmetric positions of the corneal
reflex in the pupils of each eye are
indicative of strabismus, which may
be measured by placing a prism
before the fixating eye until the
reflection is similarly positioned in
both eyes
• Base out prism for esotropia
• Base in prism for exotropia
• This is the direct reading of the squint
angle.

38. Bruckner test
• Is performed by using direct
ophthalmoscope to obtain a
red reflex simultaneously in
both eyes.
• If there is strabismus , the
deviated eye will have a
lighter and brighter reflex
than the fixing eye.
• Media opacities, Refractive
errors, Strabismus

39. Dissimilar image tests
Maddox wing
Dissociates eyes for near
fixation (1/3 m)
• Measures heterophoria
•
Maddox rod
White spot converted into red streak
• Cannot differentiate tropia from phoria
•

40. Measurements of ocular
misalignment
• Synoptophore - picture
test
• Measure misalignments, sensory
and motor fusion and
stereopsis
• Predict BV post-surgery
• Measure misalignments
9 positions of gaze

41. Key notes
• Early intermittent neonatal misalignment
common between birth and 2-4 months
• BSV well established from 6 months
• Sensitive period for development of vision and
binocular reflexes
• Suspected squint after 4 months (corrected)
age should be referred for orthoptic
assessment

42. Aniseikonia
• Translated from Greek aniseikonia means
"unequal images".
• It is a binocular condition, so the image in one
eye is perceived as different in size compared
to the image in the other eye.
• Two different types of aniseikonia can be
differentiated: static and dynamic aniseikonia
42

43. Aniseikonia
• Static aniseikonia or aniseikonia in
short means that in a static situation
where the eyes are gazing in a
certain direction
• The perceived (peripheral) images
are different in size
43

44. Aniseikonia : Static
44

45. Aniseikonia
• Dynamic aniseikonia or (optically
induced) anisophoria means that the
eyes have to rotate a different amount
to gaze (i.e. look with the sharpest
vision) at the same point in space
• This is especially difficult for eye
rotations in the vertical direction
45

46. Aniseikonia : Dynamic
46

47. Prismatic effect of decentred lens
• Convex lens  two
prisms cemented
together at their
BASEs
• Concave lens  two
prisms cemented
together at their
APEXs
• Decentred lens 
Prism effect  Base in
or Base out
Decrease convergence
Increase convergence

48. Anisophoria
• Is a condition in which the balance of the
vertical muscles of one eye differs from that
of the other eye  the visual lines do not lie
in the same horizontal plane
• Eye muscle imbalance  the horizontal visual
plane of one eye is different from that of the
other
48

49. Amblyopia
Type :
• Strabismic amblyopia
– Frequently  in esotropia patients
• Anisometropic (Refractive) amblyopia
– Difference in refraction greater than 2.50 D
• Isoametropic amblyopia
– Bilateral refractive error grater than + 5.00 or – 10.00 D
• Deprivation amblyopia
– Caused by such as media opacities
Deborah Pavan-Langston, 2008
49

50. Management of squint
•
•
•
•
•
Orthoptic assessment
Cycloplegic refraction & fundoscopy
Correct significant refractive error
Allow for refractive adaptation (up to 6/18)
Occlusion treatment for amblyopia (patches,
atropine)
• Orthoptic exercises (intermittent deviations)
• Surgery

51. Binocular Single Vision

52. Early history
Leonardo Da Vinci had realized that two images
would be needed for stereo viewing, but never
created a 3D painting

53. • 1838 Wheatstone Stereoscopes
– 1848 Brewseter
– 1881 Popularized by Oliver Wendell Holmes
• 1853 Earliest Anaglyph photographs
Viewmaster
1939-Today Equivalent

54. 20 Century
th
• 1908 Lippmann, Integral Imaging, Lenticular Printing
• 1934 Polarizing Glasses (two synchronized projectors)
• 1950s Anaglyph and polarizing glasses popular to counter
rise of television
• Next 3D picture and 3D motion picture

55. Journal of Medical Science and Clinical Research
Volume1||Issue3||Pages149-154||2013
New Approach In Binocular Single Vision Assessment For
Candidate Of Phacoemulsification Micro Surgeons
Gede Pardianto1, Diyah Purworini2
Department of Ophthalmology, Komang Makes Hospital Belawan, Medan, North
Sumatra, Indonesia
2
Putri Hijau Hospital, Medan, North Sumatra, Indonesia
1

56. BSV
• State of simultaneous vision
• Coordinated use of both eyes
• Blending of sight from the two eyes to form a
single percept

57. BSV
• Normal
– it is bifoveal
– there is no manifest deviation.
• Anomalous
– images of the fixated object are projected from
the fovea of one eye and an extrafoveal area of
the other eye

58. BSV: Requires
• Clear Visual Axis in both eyes
• The ability of the retino-cortical to promote
the fusion of two slightly dissimilar images 
Sensory fusion
• The precise co-ordination of the two eyes for
all direction of gazes to deal with two images
 Motor fusion

59. BSV: Advantage
•
•
•
•
Single vision.
The most precise kind of depth perception
Enlargement of the field of vision
Compensation for blind spot and other
differences

60. BSV
3 levels
– Simultaneous perception ( 2 images seen)
– Fusion (Interpreting 2 images as one)
– Stereopsis (3-D appreciation)

61. Development of BSV
Most neonates show coarse re-fixation
1.Conjugate fixation 1st to develop (eyes follow
object together)
2.Disjugate fixation (follow approaching object –
convergence)
3.Fusional reflex (correct for change in image
position)
4.Kinetic reflex (controlled accommodation &
convergence)

62. Stereo fusion
• Objects are “fused” when brain interprets
disparate images in the two eyes as being
the same object and perceives the depth of
the objects
• When disparity gets too large
– Double vision,
– or brain ignores input from one eye

63. Corresponding points
• Pairs of points on each retina share a common
visual direction
• A point on the nasal retina of one eye will
have a corresponding point on the temporal
retina of the other eye

64. Normal retinal correspondence
• Retinal correspondence is called normal when
both the fovea have a common visual
direction
• The retinal elements nasal to the fovea in one
eye corresponds to the retinal elements
temporal to the fovea in the other eye

65. Abnormal retinal correspondence
• The fovea of one eye has a common visual direction
with an extrafoveal area in the other eye
• This results in the eyes seeing binocularly single
inspite of a manifest squint
• When the normal eye is closed the extrafoveal
element loses any advantage over the fovea of that
eye  central fixation is over handled by the fovea
 the anomalous eye moving to primary position 
this is the basis of the cover test

66. Retinal rivalry
• When dissimilar contours are presented to
corresponding retinal areas  fusion
becomes impossible  retinal rivalry  leads
to confusion.
• In order to remove this confusion  image
from one of the eyes is suppressed.

67. Horopter
A horopter is an infinitely thin plane drawn
through all object points that project onto
corresponding retinal points.

69. Panum’s fusional area
• Range of depth’s that can be “fused”
Panum’s
fusional area

72. Binocular Convergence
θ
θ

73. Monocular Cue
• Non-stereo depth cue
• One eye can judge its
• Patients with binocular vision defect  still
can feel the depth perception

74. Monocular Cue
• Occlusion  near objects block the view of distant
objects
• Apparent size  if two objects are actually the same
size, but one appears smaller, then the small one is
farther away than the larger  relative size
• Motion parallax and Relative velocity near objects
appear move faster than distant objects
• Light and Shading  distance and colour
• Overlapping contour*

75. Relative size

76. Motion parallax

77. Motion parallax
• Translocation of the head
• Cause the images of near objects to move
opposite the head
• The images of far objects to move with the
head
• Assuming the fixation point is at an
intermediate distance

78. Light and shade

79. Over-lapping contours

80. Monocular cue
• Perspective  parallel lines converge in the
distance
• Aerial perspective
• Geometric perspective
• Texture  becomes finer with distance
• Colour change  colour becomes more blue
with distance  Atmospheric effect
• Haze  objects become fuzzy in the distance
• Accommodation  our brain knows how hard
our eyes are working to focus

81. Aerial perspective

82. Geometric perspective

83. Refractive age

84. Depth perception
 Monocular cues
 Non stereoscopic binocular clues
 Stereopsis

85. Why fovea/periphery differences
• Range of disparities in natural scenes.
• Fovea - high depth acuity.
• Periphery - provides coarse information about
where to make convergence eye movements.

86. Mistake in BSV
• Motoric
– Squint
• Refractive
– Aniseikonia
• Eye Sensoric
– Amblyopia
• Optical problems
– Visual illusion
• Brain Perception
– Experience
– Monocular cues
– Visual illusion

87. Visual illusion

88. Visual illusion

89. Visual illusion

90. Visual illusion

91. Visual illusion

92. Size illusion

93. Beuchet chair

94. Beuchet chair

95. Ames room

96. Ames room

97. Visual illusion: Shadow effect

98. Visual illusion: Shadow effect

99. Visual illusion: just 2D

100. Visual illusion: Moving texture

101. Visual illusion: Colour

102. Visual illusion: Grid illusion

103. Visual illusion: Bleeped-up

104. Visual illusion: The confuse

105. Visual illusion: Floor painting

106. Visual illusion: Single photo

107. Visual illusion: Single photo

108. Visual illusion: Bistable

109. Visual illusion: Bistable

110. Visual illusion: Bistable

111. Visual illusion: Mirage
A inferior mirage occurs when the air
below the line of sight is hotter and
has lower index bias than the air
above it.
A superior mirage occurs when the
air below the line of sight is colder
than the air above it.

112. Mirage: hot haze
Heat shimmer  refers to the inferior mirage
experienced when viewing objects through a
layer of heated air

113. Visual illusion: Moonbow

114. Visual illusion: Halo
A sun dog (or sundog), mock sunor phantom
sun, scientific name parhelion (plural
parhelia), is an atmospheric phenomenon
that creates bright spots of light in the sky,
often on a luminous ring or halo on either side
of the sun.
Sundogs may appear as a colored patch of
light to the left or right of the sun, 22° distant
and at the same distance above the horizon
as the sun, and in ice halos.
They can be seen anywhere in the world
during any season, but they are not always
obvious or bright.
Sundogs are best seen and are most
conspicuous when the sun is low.

115. Sunset green flash
The optical phenomenon known as the green
flash can occur at sunrise or sunset, and it’s
most often seen over low, unobstructed
horizons such as the ocean.

116. Sun pillar
A Sun pillar is an atmospheric phenomenon
caused when high-altitude ice crystals reflect
the rising or setting Sun’s reddened light.

117. Scintillation or Grid illusion

118. Visual illusion: Optic
1. Thermal Inversion
The Titanic was sailing from
Gulf Stream waters into the
frigid Labrador Current, where
the air column was cooling
from the bottom up, creating a
thermal inversion: layers of
cold air below layers of
warmer air.
Extraordinarily high air
pressure kept the air free of
fog.

119. Visual illusion: Optic
2. Superior Mirage
A thermal inversion
refracts light abnormally
and can create a superior
mirage: Objects appear
higher (and therefore
nearer) than they actually
are, before a false horizon.
The area between the
false horizon and the true
one may appear as haze.

120. Visual illusion: Optic
3. Iceberg Camouflage
The Californian’s radio
operator warned the Titanic of
ice. But the moonless night
provided little contrast, and a
calm sea masked the line
between the true and false
horizons, camouflaging the
iceberg.
A Titanic lookout sounded the
alarm when the berg was
about a mile away—too late.

121. Visual illusion: Optic
4. Mistaken Identity
• Shortly before the collision,
the Titanic sailed into the
Californian’s view—but it
appeared too near and small
to be the great ocean liner.
• Californian captain Stanley
Lord knew the Titanic was the
only other ship in the area
with a radio, and so concluded
this ship did not have one.

122. Visual illusion: Optic
5. Morse Lamp
• Lord said he repeatedly
had someone signal the
ship by Morse lamp “and
she did not take the
slightest notice of it.”
• The Titanic, now in
trouble, signaled the
Californian by Morse lamp,
also to no avail.
• The abnormally stratified
air was distorting and
disrupting the signals.

123. Visual illusion: Optic
6. Distress Rockets Ignored
• The Titanic fired distress
rockets some 600 feet into
the air—but they appeared to
be much lower relative to the
ship.
• Those aboard the Californian,
unsure of what they saw,
ignored the signals.
• When the Titanic sank, at 2:20
a.m. April 15, they thought the
ship might be simply sailing
away.

124. Conflicting Cues: Only binocular
• Random Dot Stereograms

125. Conflicting Cues: Only binocular
• Random Dot Stereograms

126. 3D ability: 3D movie
The archetypal 3D glasses, with modern red
and cyan color filters, similar to the red/green
and red/blue lenses used to view early
anaglyph films.

127. 3D ability: 3D movie
Resembling sunglasses, polarized glasses are
now the standard for theatrical releases and
theme park attractions.

128. 3D ability: 3D movie
A pair of LCD shutter glasses used to view
XpanD 3D films. The thick frames conceal the
electronics and batteries

129. 3D vision ability

130. 3D vision ability

131. 3D vision ability

132. 3D vision ability

133. 3D vision ability

134. 3D vision ability

135. 3D vision ability

136. 3D vision ability

137. 3D vision ability

138. 3D vision ability

139. 3D vision ability

140. 3D vision ability

141. 3D vision ability

142. 3D vision ability

143. 3D Vision: Game

144. The hidden tiger

145. Shape of life: Pareidolia

146. Loch Ness Monster

147. Loch Ness Monster

148. Beyond the lecture
•
•
•
•
•
I have seen with my own eyes!
So now…
What do you think?
Seeing doesn’t mean believing
Think again!