It details about the sensory development, theories and the neural aspects of binocular vision development along with various tests involved to assess stereopsis.

1. BINOCULAR SINGLE VISION
By
Lavanya Kalikivayi, M.Opt., FLVPEI., FIACLE., (Pursuing PhD)
Associate Professor
Ahalia School of Optometry & Research Centre

2. State of simultaneous vision
with two seeing eyes that
occurs when an individual fixes
his visual attention on an object
of regard.
It is the co-ordinated use of
both eyes to produce a single
mental impression.
DEFINITION

3. 1. Optical defects in one eye are made less obvious by the
normal image in the other eye
2. Defective vision in one part of the visual field is masked
because the same image falls on the functioning area of the
other retina.
3. Field of vision is definitely larger.
4. Allow the individual to converge the line of sight and obtain
a reading as to the absolute distance of objects.
5. Presence of stereopsis.
ADVANTAGES

9. OCULOCENTRIC (MONOCULAR)
EGOCENTRIC (BINOCULAR)
VISUAL DIRECTIONS

10. When an object is viewed, its image falls on the
foveola. visual direction -represented by principle
visual line or axis
Each point on retina can have its own visual axis
For a given eye position , objects having
superimposed retinal images will be seen in as
being in alignment in visual field (law of OC visual
direction)
OCULOCENTRIC
(MONOCULAR)

11. Frame of reference(single system of VD) is head
(egocentric) rather than 2 eyes.
Visual space is seen with imaginary single
eye(cyclopean eye)
Herring’s law of identical visual direction – fovea
have a common subjective visual direction.
EGOCENTRIC (BINOCULAR)

12. PRE-REQUISITES FOR DEVELOPMENT
OF BSV
Motor Mechanism:
•Correct neuromuscular development so that the visual axes
are directed at the object (FIXATION)
•Overlap of visual fields
Sensory Mechanism:
•Approximately equal image clarity and size in the two eyes
•Corresponding retinal areas (cyclopean eye)
•Normal visual pathways
Mental Process:
•Ability of visual cortex to promote binocular single vision

13. Depends on:
1. Visual acuity value of retinal receptors of
each eye.
2. Normal Correspondence of retinal receptors
of the two eyes.
3. At hemidecussation of the optic nerve fibre at
Optic Chaisma and integrity of apparent
visual pathway.
4. Proprioceptive impulses from the extrinsic
ocular muscles.
SENSORY
MECHANISM

14. 1. It depends on adequate degree of central
vision (Fovea and Macula) and of the
refracting media of the eye ( Cornea, Aqueous
, Lens , Vitreous).
2. A certain degree of comparability of the two
eyes with regard to their refraction ( i.e. the
size difference of two retinal images is not too
great to prevent their fusion, Anisekonia)
FACTOR OF VISUAL ACUITY VALUE OF
RETINAL RECEPTORS OF EACH EYE

15. Extreme temporal part of the
peripheral visual field is
UNIOCULAR but the whole of
rest of total visual field is binocular
due to almost complete overlap of
separate visual fields.
Stimulation of Corres. Retinal
Points results in formation of
SINGLE MENTAL
IMPRESSION despite the
existence of two separate patterns
of stimulation one from each eye.
FACTOR OF NORMAL CORRESPONDENCE
OF RETINAL RECEPTORS OF THE EYES

16. Corresponding retinal elements are those
elements of the two retinae, the stimulation of
which in binocular vision, gives rise to
localization in one and same visual direction .
The retinal receptors in both eyes that dictate a
common visual direction under binocular
conditions are called corresponding points or
elements.
RETINAL CORRESPONDENCE

17. CORRESPONDING RETINAL
POINTS
Retinal elements of two eyes that
share a common subjective
visual direction
– Example
• Fovea of two eyes
• Temporal retinal points of a
eye – Nasal retinal points of
the fellow
eye & vice versa

18. CONTD.....
Rest other retinal points
– Non corresponding /disparate
Significance:
– Corresponding retinal elements are principal
elements of the two retinas that give rise in
binocular vision
–Single vision is the hallmark of retinal
correspondence

20. HOROPTER
Horopter is defined as
the locus of all object
points that are imaged on
corresponding retinal
elements at a given fixed
distance.
Horizon of vision

21. CONTD....
Object points lying on the
horopter
- seen single
- Object points off the horopter
- Seen double
- Feature
2 Dimensional plane
Shape
Fronto-parallel plane :
Longitudinal curve

22. THEORETICAL HOROPTER
CURVE
Veith-Muller Circle
If corresponding retinal
points have a regular
horizontal distance from
the fovea of each eye
Shape of Horopter
-Circle passing through
the centre of rotation
of two eyes and the
fixation point

23. EMPIRICAL HOROPTER CURVE
Hering and Hillebrand - showed
Vieth-Mu¨ller circle does not describe
the longitudinal horopter.
Empirical horpter :
- Flatter than thoeritical horopter
- Distribution of the corresponding
retinal elements are not the same in
the nasal & temporal parts of retinas
- Shape varies from person to
person

24. HERING-HILLEBRAND
HOROPTER DEVIATION
The discrepancy (difference) between theoretical horopter
and the empirical horopter .
- Can be attributed to disturbing optical properties of the
ocular media.

25. HOROPTER CURVE

26. PANUM’S FUSIONAL AREA &
SPACE
In reality a retinal point of an eye is not only
corresponding to a point but to a retinal area of other
eye
Panums area- the retinal area surrounding the corresponding
retinal points within which BSV can be maintained.
Panums space: A narrow band around the horopter within
which objects gives rise to BSV
So objects located slightly off the horopter can remain single
• Object stimulates slightly non-corresponding points

27. SIZE OF PANUM’S FUSIONAL AREA
Increases with Retinal
Eccentricity-
– At fovea
• 6-10’ of arc
– 120 eccentricity
• 30-40’ of arc

28. PANNUMS FUSIONAL AREA

29. PHYSIOLOGICAL DIPLOPIA
The Diplopia elicited by an object
point off the Pannum’s fusional
area
Types
A.Crossed (Heteronymous)
Diplopia
Temporal (crossed)
disparity
B.Uncrossed (homonymous)
Diplopia
Nasal (uncrossed) Disparity

33. It is dependent on hemidecussation because this
enables nerve fibers from corresponding retinal
areas of the two eyes to become associated with
one another ultimately in the visual area of the
occipital cortex.
FACTORS AT HEMIDECUSSATION OF THE OPTIC
NERVE FIBER AT OPTIC CHIASM AND
INTEGRITY OF APPARENT VISUAL PATHWAY

35. Extrinsic ocular muscles provide the brain with
sensory information of a proprioceptive nature.
THE FACTOR OF PROPRIOCEPTIVE IMPULSES
FROM THE EXTRINSIC OCULAR MUSCLES

36. Maintenance of correct positional relationship at
rest and in motion.
MOTOR MECHANISMS

37. Postural Reflex:
Maintenance of the two eyes in their correct
relative positions within the orbits so that the
visual axes are aligned correctly to one another
despite changes in the movement of head relative
to the body or of the body relative to space in
the absence of any visual stimulus .
They are entirely unconditioned reflexes.
PHYSIOLOGICAL FACTOR

38. a) Static postural reflex: Changes in the position of head
relative to body. Controlled by part of labyrinth: utricle
and saccule and proprioceptive impulses from neck
muscles. e.g. proprioceptive head turning reflex or “the
dolls head phenomenon”
b) Stato-kinetic reflex: Changes in the position of head
relative to space, in response to movements of
acceleration and deceleration. Controlled by semi-
circular canals.”Puppenhof’s phenomenon”
TWO TYPES:

39. • Maintenance of two eyes in their correct
positions within the orbits so that visual axes
are aligned correctly with one another despite
changes in movement of the head relative to
the body or of the body relative to space as a
result of visual stimuli which reach the visual
cortex by afferent visual pathway.
• They are conditioned reflexes.
FIXATION REFLEX (PSYCHO-
OPTICAL):

40. 1. Fixation reflex:
Ability of each eye to fix a definite object.
Dependent on presence of adequate field of
vision and functioning fovea.
This reflex is present at birth but only to a feeble
extent.
It is initiated with afferent visual stimuli.
TYPES

41. 2. RE-FIXATION REFLEX:

42. Application of fixation reflexes to both eyes at same time so
that they retain fixation during the conduct of conjugate
movements.
Well established at age of 6 months.
4. Disjunctive or Vergence fixation reflex:
Application of fixation reflex to both eyes at the same time so
that the eyes retain fixation movements during the conduct of a
disjunctive movement.
Reflex is later in development than the conjugate fixation
reflex but it is well established by the age of 6 months.
3. CONJUGATE-FIXATION
REFLEX:

43. Elaboration of the conjugate and disjunctive
fixation reflexes which permits the eyes to
function binocularly even under condition of
stress.
It functions to some extent in the first year but is
fully developed after the age of about 5 years.
5. CORRECTIVE-FUSION
REFLEX:

44. Maintenance of two eyes in their correct relative
position within the orbits as a result of controlled
accommodation-convergence relationship.
KINETIC REFLEX:

46. The function of visual cortex to perceive a single
mental impression of an object despite the fact
that the object is viewed separately by the two
eyes.
The image of an object is build up on two
separate halves with the object divided vertically.
A. FACTOR OF FUSION:

48. B. FACTOR OF CORTICAL
MOTOR CONTROL:
Centres in frontal and occipital parts of cerebral
hemispheres control the intermediate centres and
cranial nuclei concerned in final efferent impulses
to extrinsic ocular muscles.

49. Vestbular Eye Movements Mature 34 weeks of gestation
Optokinetic Nystagmus At birth
Conjugate Horizontal Gaze At birth
Turning Head To Fixate An Object 2 to 3 weeks
Sustain Monocular Fixation Of Large Near Objects 4 to 5 weeks
Conjugate Vertical Gaze 2 months
Binocular Fusion 3 months
Accommodation Mature 4 months
Stereopsis 6 months
Fusional Movements Firmly Established 1 YR
Adult Level Visual Acuity Reached 2-3 yr
DEVELOPMENT OF BINOCULAR
VISION

50. VISUAL AXIS

51. FIXATION DISPARITY
It is the minute image displacement, rarely exceeding
several minutes of arc of angle, occurs within Panum’s
space while fusion is maintained.
• Due to presence of pannum’s fusional area
– A physiological variation in placement of retinal image
displacement from corresponding retinal points
• Even Allow fusion
• Displacement of retinal images in two eyes
– Retinal disparity

52. FIXATION DISPARITY
It is the minute image
displacement, rarely exceeding
several minutes of arc of angle,
occurs within Panum’s space while
fusion is maintained.
• Due to presence of pannum’s fusional area
– A physiological variation in placement of retinal image
displacement from corresponding retinal points
• Even Allow fusion
• Displacement of retinal images in two eyes
– Retinal disparity

53. Grades of Binocular Vision

54. GRADES OF BINOCULAR VISION
There are three grades of binocular vision as given
by Worth's classification:
Grade I : Simultaneous Macular perception (SMP)
Grade II : Fusion
Grade III : Stereopsis

55. 1.SIMULTANEOUS MACULAR
PERCEPTION
 Simultaneous perception exists when signals
transmitted from the two eyes to the visual cortex
are perceived at the same time.
 It consists of the ability to see two dissimilar
objects simultaneously.

56. 2. FUSION
Defined as the cortical unification of visual objects into
a single percept that is made possible by the
simultaneous
stimulation of corresponding retinal areas.
In simple words,
It is the ability of the two eyes to produce a composite
picture
from two similar pictures each of which is incomplete
in one small detail

57. COMPONENTS OF FUSION
Sensory Fusion
-the unification of visual excitations from corresponding retinal images into a single
visual percept, a single visual image
-The ability to unify images falling on corresponding retinal areas.
Motor Fusion
- It is a vergence movement that causes similar retinal images to fall and be maintained
on corresponding retinal areas.
• Ability to align the eyes in such a manner that sensory fusion can be
maintained
• Diplopia preventing mechanism

58. The normal fusional range is 35/40 PD base
out and 16 PD base in on near reading.
16PD base out and 8PD base in on distance
testing.
Source: Rowe Fiona. Clinical Orthoptics 2nd Ed, Blackwell Publishing,2004 2: 23

59. 3. STEREOPSIS
It is the ability to fuse images that stimulate horizontally
disparate retinal elements within Panum’s fusional area resulting
in binocular appreciation of visual object in depth i.e. in 3D
– Retinal disparity (Fixation disparity) is the basis of
3 D perception
– Stereopsis occurs when
• Retinal disparity is large enough to simple fusion
but small enough to cause diplopia

60. Stereopsis & depth perception are not
synonymous.
Not a form of simple fusion.
Normal stereoacuity is considered to be 40
sec of arc
CONTD....

61. First degree
simultaneous perception
2nd degree
flat fusion
3rd degree
Stereopsis
From Rosenbaum & Santiago Clinical Strabismus Management

62. Fusion
Corresponding retinal
elements are stimulated
Motor system is required
Fusion can occur without
streopsis
Fusion occurs horizontal or
vertical corresponding retinal
points
THE DIFFERENCE
Stereopsis
 Non corresponding retinal
elements are stimulated
 Motor system is not
required
Without fusion it can not
occur
Stereopsis occurs only with
horizontal disparity

63. Perception of distance of objects from each
other or from the observer.
Several clues contribute-
A] BINOCULAR CLUE: Stereopsis.
B] MONO OCULAR CLUES:
PERCEPTION OF DEPTH

64. oStereopsis a fucntion of spatial
disparity
oLocal and global stereopsis
oFine v/s coarse stereopsis
oStereopsis and fusion
PHYSIOLOGICAL BASIS OF
STEREOPSIS

65. •Perception of distances from object from each
other or from observer.
•It is independent of the appreciation of 3-D and
depends on various factors:
Stereopsis
Non Stereoscopic Clue – Retinal Disparity
Monocular./Non Stereoscopic Clues
Accomodation And Convergence
DEPTH PERCEPTION

66. 1. Theory of correspondence and disparity
(most widely accepted theory)
2. Neurophysiological basis
3. Alternation theory of Binocular Vision
4. Projection theory of Binocular Vision
5. Motor theory
6. Theory of isomorphism
Theories of BSV
Older theories

67. THEORY OF CORRESPONDENCE
AND DISPARITY
-Simultaneous stimulation of the corresponding points by
one object transmits single visual impression with no depth
quality.
-Simultaneous stimulation by two object points that differ in
character results in binocular rivalry.
-Diplopia occurs when disparate elements are stimulated by
one object.
- Binocular single vision with stereopsis results when the
horizontal disparity remains within the limits of Panum’s
area.

68. 2 different visual pathways from different population of
retinal ganglion cells.
Parvo and Magno cellular pathway- lateral geniculate body.
P cells- colour, fine 2 point discrimination and project to the
areas of fovea
M cells- direction, motion, speed, flicker, gross binocular
disparities. Project to the areas of Parafoveal and peripheral
retina
In striate cortex- p & m-recipient lamellae are segregated. M
cells go predominantly to parieto-occipital areas, P cells to
temporo-occipital areas. But there are inter-connecting
pathways, so information overlaps.
NEUROPHYSIOLOGY OF DEVELOPMENT

69. RETINAL
GANGLION
CELL
LGB
LAMINA V1 V2
CORTEX
OTHER
Alpha Magno-
cellular
4 beta Thick stripes V2 motion
Beta Parvo-
cellular
4 alpha Inter-stripes V4, Static
stereopsis
Beta Parvo-
cellular
4 alpha Thin stripes V 4, colour
PARALLEL VISUAL PATHWAYS

70. MAGNOCELLULAR PARVOCELLULAR
I. Perception Thick stripes
• Motion
• Flicker
• Transient luminance
a. Interblob-interstripe
• High spatial frequency
acuity
• Some colour
b. Blob thin stripe
• Colour
• Low spatial frequency
acuity
II. Stereopsis • 40” – 80”
• Local
• Non cyclopean
• Coarse
• Motion
a. Interblob-interstripe
• 6” – 1000”
• Global
• Cyclopean
• Fine
• Static
b. Blob-thin stripes
• Depth tilt
III. Ocular motor • Pursuit
• Vergence initiation
• Vergence maintenance
COMPARISON OF VISUAL PROCESSING SYST

72. Monocular clues for depth
perception

73. Relative size
Interposition
Linear perspective
Aerial perspective
Distribution of lights & shadows.
Motion parallax

74. RELATIVE SIZE

75. INTERPOSITION

76. LINEAR PERSPECTIVE

77. AERIAL PERSPECTIVE

78. DISTRIBUTION OF LIGHTS &
SHADOWS.

79. MOTION PARALLAX

80. Advantage and disadvatages of BSV

81. ADVANTAGE OF HAVING BSV
• Stereopsis
• Binocular summation.
– vision shaper, clearer &
more sensitive
• Larger field of view.
• Spare eye
visual field

82. Confusion
Diplopia
Suppresion
Eccentric fixation
Abnormal retinal correspondence(ARC)
Amblyopia
ABNORMAL BINOCULAR VISION

83. When dissimilar contours presented to corresponding retinal
areas, does not fuse it’s k/a Retinal Rivalry; eg. Uniform
surfaces of different colour, unequal luminances of two
targets
Response – Suppression (innate involuntary process)
whereby the signals coming from certain retinal elements are
ignored in favor of those coming from another part
1st line of defense in against pathological interruption; e.g.
Marked refractive error in one eye, strabismus.
RETINAL
RIVALRY AND
SUPPRESSION

84. RETINAL RIVALRY

85. Normal retinal correspondence
Abnormal retinal correspondence(ARC)
ARC is an active cortical adjustment in the
directional values of the two eyes which occur in a
child with early onset of squint.
The fovea of one eye and a peripheral retinal
element of the other eye acquire a common visual
direction.
ARC is more common in esotropia than in
exotropia
It is less common in vertical deviations & intrue
RETINAL CORRESPONDENCE

86. SUPPRESSION CLASSIFICATION
Central versus peripheral.
Central suppression is the term used to describe the mechanism that keeps
the foveal image of the deviating eye from reaching
consciousness, thereby preventing confusion
Peripheral suppression is the mechanism that eliminates diplopia by
preventing awareness of the image that falls on the peripheral
retina in the deviating eye, the image that resembles the image
falling on the fovea of the fixating eye.
This form of suppression is clearly pathologic, developing as a
cortical adaptation only within an immature visual system,
Adults may be unable to develop peripheral suppression and
therefore may be unable to eliminate the peripheral second image
of the object viewed by the fixating eye (the object of regard)
without closing or occluding the deviating eye,

87. SUPPRESSION CLASSIFICATION
Nonalternating versus alternating. If suppression is
unidirectional or always causes the image from the
dominant eye to predominate over the image from
the deviating eye, the suppression is non alternating.
This type of mechanism may lead to the
establishment of strabismic amblyopia.
If the process is bidirectional or switches overtime
between the images of the 2 eyes, the suppression is
described as alternating .

88. SUPPRESSION CLASSIFICATION
Facultative versus obligatory.
Suppression may be considered facultative if Present only when the eyes
are in the deviated state and absent in all other states.
Patients with intermittent exotropia, for instance, often
experience suppression when the eyes are divergent but may
enjoy high-grade stereopsis when the eyes are straight.
In contrast, obligatory suppression is present at all times, whether the eyes
are deviated or aligned.
The suppression scotoma in the deviating eye may be either
relative (in the sense of permitting some visual sensation) or
absolute (permitting no perception oflight).

89. ANOMALOUS RETINAL
CORRESPONDENCE
Anomalous retinal correspondence (ARC) can be described as a condition
wherein the fovea of the fixating eye has acquired an anomalous common
visual direction with a peripheral retinal element in the deviated eye.
The 2 foveas have different visual directions.
ARC is an adaptation that restores some sense of binocular cooperation.
Anomalous binocular vision is a functional state superior to that prevailing in
the presence of total suppression.
In the development of ARC, the normal sensory development is replaced only
gradually and not always completely.
The more long standing the deviation, the more deeply rooted the ARC may
become.
The period during which ARC may develop probably extends through the first
decade of life.

90. ANOMALOUS RETINAL
CORRESPONDENCE
Paradoxical diplopia can occur when ARC persists after
surgery.
When esotropic patients whose eyes have been set straight or
nearly straight report, postoperatively, a crossed diplopic
localization of foveal or parafoveal stimuli, they are
experiencing paradoxical diplopia.
Clinically, paradoxical diplopia is a fleeting postoperative
phenomenon, seldom lasting longer than a few days to
weeks.
However, in rare cases, this condition has persisted for
much longer.

91. Harmonius arc
Un harmonius arc
Paradoxical
HARMONIUS angle of anamoly= angle of strabismus
UNHARMONIUS angle of anamoly< angle of strabismus
PARADOXICAL angle of anomaly is in the opposite direction
ABNORMAL RETINAL
CORRESPONDENCE

92. ADVANTAGES OF ARC DISADVANTAGES OF ARC
•Form of BSV is present Once developed, extremely difficult to
establish normal correspondence.
•Stabilises the angle of deviation pre-
operatively
Post-operatively, the angle of deviation
may increase sometimes.
•Has a better visual judgement since
some binocular appreciation of depth is
present

93. Confusion
Diplopia
Supression central vs peripheral
monocular vs alternate
facultative vs obligatory
ABNORMALITIES IN BSV

94. ANAMOLIES OF BINOCULARITY
Confusion
When squinting occurs the two foveas view two different
objects that are physically separated in objective space,
and send two different images to a single cortical
perceptual area. This leads to confusion.
Diplopia
When squinting occurs an object in space is perceived by
the fovea of one eye and some other extra-foveal point of
the other eye, which has a different projection or
localization value in space. Thus an object would be
localized twice in space causing diplopia.

96. BEGINS AT 2-3 MONTHS MATURE AT BIRTH
IF DEPRIVED NEVER DEVELOPS WILL NOT DEPRIVE
POOR VN AND NYSTAGMUS --
SEVERES FIXATION ---
ONCE DEVELOPED
REINFORCEMENT REQUIRE TILL 9
YRS AGE
---
OTHERWISE AMBLYOPIA
DEVELOPS
---
CONES AND PARVOCELLULAR
GANGLION CELLS
RODS AND MAGNOCELLULAR
ANGLION CELLS
14’ OF ARC OF STEREOPSIS 200’ ARC OF STEREOPSIS
MACULAR EXTRAMACULAR

97. BV MACULAR EXTRAMACULAR
SIMULTANEOUS
PERCEPTION
NONE EXCELLENT
FUSION EXCELLENT LIMITED
STEREOPSIS EXCELLENT LIMITED
SO THERE ARE NO ADAPTATIONS IF MACULAR
BINOCULAR VISION IS IMPAIRED AND
THERE WILL BE LIMITED FUSION AND
STEREOPSIS
IF EXTRAMACULAR BV IS IMPAIRED
SUPPRESSION AND ARC TAKES PLACE

98. a) SYNAPTOPHORE/STEREOSCOPE TEST
b) VECTOGRAPH TEST - TITMUS STEREO TEST
 Fly test
 Animal test
 Circles test
c) RANDOM DOT STEREOGRAM TEST
 RD ‘E’ test
 TNO RDT
 Lang test
d) MOTOR TASK
TEST FOR
STEREOPSI
S

99. EYES MUST BE DISSOCIATED
MUST BE PRESENTED WITH SEPERATE FIELD OF VIEW
EACH FIELD MUST CONTAIN ELEMENTS IMAGED ON
CORRESPONDING RETINAL AREAS
FEATURES FOR STEREOPSIS
TEST

100. DOT GRADED
STEREO SLIDES FOR
THE QUANTITATIVE
MEASUREMENT OF
STEREOPSIS.(760-90
SEC OF AN ARC)

101.  It consists of Polaroid material on which the two
targets are imprinted
 Each target is polarized at 90 degree with respect to the
other.
 Use of polaroid spectacles.
 It is a 3D Polaroid vectograph which is made up of
two plates in a form of
booklet.
Advantages : simple and easy to perform.
Disadvantages : unreliability in differentiating patients
with amblyopia and heterotropia
VECTOGRAPH TEST - TITMUS STEREO TEST

102. FLY TEST
• USEFUL IN YOUNG CHILDREN
• TEST GROSS STEREOPSIS
• THRESHOLD 3000 SEC OF ARC

103. ANIMAL &
FLY TEST

104. It is performed if the gross stereopsis is present
 3 rows of 5 animals
 One animal from each row is imaged disparately(threshold of
10, 200 and 400 sec of arc respectively).
 In each row one of the animals correspondingly imaged in two
eyes is printed heavily black which serves as a misleading clue.
 The subject is asked which one of the animals stands out.
 A subject without stereopsis will name the animal printed
heavily while in the presence of stereopsis he will name the
disparately imaged animal .
ANIMAL
TEST

105.  Only one of the circles in each square is imaged disparately at
random with threshold from 800 to 40 sec of arc.
 If the subject has passed other two tests, he is asked to push
down the circle that stands out, beginning with the first set.
 Circle no. 5 (100sec of arc) is considered lowest limit of fine
central stereoacuity & designated as the lowest limit of good
stereoacuity.
CIRCLE
TEST

106. RDT ‘E’ Test
All three cards should be viewed with Polaroid
glasses.
Card A : bas relief model of the stereo test figure
and is used to show the patient for what he
should look.
Card B : it contains the ‘E’ stereo figure with a
random dot background.
Card C : it is stereo blank with an identical random
dot background.
Card b and c are held at distance of 50cm and pt is
asked to indicate which card contains the letter
‘E’.
The stereo acuity when present can be quantitated
RANDOM
DOT TESTS

108.  It is to provide retinal disparities ranging from 15 to 480
sec of arc.
 Advantage of testing quantitative responses without
changing the testing distance.
 It consists of seven plates.
 Each plate consists of stereogram in which various shapes
have been created by random dots in complementary
colours.
 First 3 stereograms of the test booklet are used to
establish the presence of gross stereopsis while remaining
four to test fine stereopsis
TNO
RANDOM
DOT TEST

110. DISTANCE RANDOT STEREOTEST

111. This stereopsis test (10ft/3m) is for patients as young as 4 years of age.
Test includes:
8 tests (4 pages) in 1 booklet (400 to 60 sec of arc)
1 pair of standard polarized glasses and 1 pair of pediatric polarized glasses
Answer key on back cover
Demonstration card
DISTANCE RANDOT STEREOTEST

112. Random dot stereogram with panographic presentation.
Seen through cylindrical lenses not polaroid glasses.
Test card held at a distance of 40cms
Disparity of car and star 600secs and cat 1200secs
LANG TEST

113. LANG TEST

114. Three transparent plastic sheets of varying thickness
On the surface of the sheet, it is printed with four squares of randomly
distributed shapes
One of the square has a hidden circle
The test does not require a special spectacle as the thickness of the sheet
creates the disparity
The disparity measured is 6000 to 15 sec of arc.
FRISBY TEST

115. FRISBY TEST

116. FRISBY TEST

117. MOTOR TESTS

118. Popularised by Lang in 1975
Effective to test gross stereopsis
Threshold value 3000-5000 sec of arc
TWO
PENCIL
TEST

119. TWO
PENCIL
TEST

120. TYPE OF TEST STEREOACUITY ACCESSORY GLASSES
USED
Braddick random dot stereo
slide
760 to 90 sec of arc Synaptophore
Fly test Gross 3000 sec of arc Polarized glasses
Animal test 10, 200 & 400 sec of arc Polarized glasses
Circle test 800 to 40 sec of arc Polarized glasses
TNO E test Gross stereoacuity,
PASS/FAIL
Polarized glasses
TNO random dot test 15 to 480 sec of arc Red & green goggles
Lang test 600 to 1200 sec of arc No filters for dissociation
Distance randot stereotest 400 to 60 sec of arc Polarized glasses
Motor test 3000 to 5000 sec of arc Hand co-ordination
TABLE FOR SEREOPSIS TEST

121. Without the basic concepts of BSV it is almost impossible to understand
strabismus and treat it.
The advantage of BSV outweights the disadvantage.
CONCLUSION