Binocular single vision refers to the state of simultaneous vision achieved through the coordinated use of both eyes to perceive a single image. It involves three main components: simultaneous perception, fusion, and stereopsis. Simultaneous perception is perceiving images from both eyes at the same time. Fusion is the cortical unification of the two retinal images into one percept. Stereopsis provides the highest level of binocular cooperation by producing a sensation of depth through the fusion of horizontally disparate retinal images. The development of binocular single vision occurs gradually in infancy and early childhood as the visual system matures and learns to coordinate the two eyes. Mechanisms such as retinal correspondence, the horopter, Panum's fusional area,

1. Binocular Single Vision
Presenter : Dr Vishnu Prasad Rao
Supervisor : Prof Dr. Shatriah Ismail

2. 01 Definition
02 Grading
03 Fusion vs Stereopsis
04 Development of BSV
05 Retinal Correspondence
06 Horopter/Pannums Fusional Area
07 Anomalies of BSV
08 Investigations
09 MCQ
Table Of
Contents

3. Definition
State of simultaneous vision which is achieved by coordinated
use of both eyes so that separate and slight dissimilar images
arising in each eye appreciated as single image by process of
vision

4. Grading
1. SIMULTANEOUS PERCEPTION
2. FUSION
3. STEREOPSIS

5. Simultaneous 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.

6. Fusion
• Fusion is the cortical unification of 2 images of an object, 1 from
each eye, into a single percept.
• For retinal images to be fused, they must be similar in size and
shape.
• For fusion of macular images (central fusion) to occur, there can
be very little dissimilarity between the images in each eye
• More image dissimilarity is tolerated in the periphery (peripheral
fusion), where the receptive fields are larger.

7. Sensory Fusion
• based on the innate, orderly topographic relationship between
the retinas and the visual cortex
• images falling on corresponding (or nearly corresponding)
retinal points in the 2 eyes are combined to form a single visual
percept.
Motor Fusion
• Motor fusion is a vergence movement that allows similar retinal
images to be maintained on corresponding retinal areas

9. Stereopsis
• Stereopsis is a binocular sensation of relative depth caused by horizontal
disparity of retinal images.
• It is the highest form of binocular cooperation.
• The ability to fuse images that stimulates horizontally disparate retinal
elements within Panum’s fusional area resulting in binocular appreciation
of visual object in depth i.e. in the third dimension
• Able to perceive width, depth, and height ,when look at an object.

10. How it occurs?
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 Retinal disparity (fixation disparity) is the
basis of 3D perception
 Stereopsis occurs when retinal disparity
is too great to permit simple
superimposition of the two retinal
images, but not great enough to elicit
diplopia

11. Stereopsis and depth perception
• Stereopsis and depth perception are not synonymous.
• Monocular cues— which include object overlap, relative object size,
highlights and shadows, motion parallax, and perspective also contribute
to depth perception.
• Monocular patients can have excellent depth perception using these cues.

12. Monocular cues for depth perception

14. Fusion vs Stereopsis
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15. Advantanges of BSV
● Results in stereopsis
● Optical defects in one eye is compensated by the
normal eye
● Enhanced visual acuity, contrast sensitivity
● Defective vision in any part of one visual field is
masked, e.g. blind spot
● Wider visual field than monocular
• Normal monocular visual field
• 60̊ superior & nasal
• 75̊ inferiorly
• 95 temporally
• With BSV : 160-200̊
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16. Development of BSV
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• Basic visual functions are innate and therefore present at birth
• Their coordination, maturation, & refinement take place during
early postnatal period

17. BSV milestones
AGE2 MILESTONES
Birth no bifoveal fixation. Monocular fixation is present at birth, but
poor
2-3 weeks infant begins to make movements, turning his eyes to fixate an
object
4-5 weeks can sustain monocular fixation of large near objects
6 weeks fixation alternates rapidly between two eyes & child begins to
fixate binocularly with conjugate pursuit movements which
are saccadic initially but become smooth and gliding by 3-
5mts of age.
3-6 months conjugate movements and disconjugate vergence movements
1 year fusional movements are firmly established.
2-3 years adult level of visual acuity is reached.
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18. Maturation of binocular function
• At birth, eyes act as 2 independent
sense organs
• Foveas are not formed until the 3rd
month
• By trial and error the child learns
that, when the image of an object is
brought on to the 2 foveas
simultaneously, the image is most
detailed
• Hence visual axes are oriented in
such a way that each fovea is
directed at the object of regard
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19. Mechanism and terminologies in BSV
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20. Visual Axis
• A visual axis is defined as a line that
connects an object point with its
image on the retina
• Types;
a) Principal
• - Fovea – area of highest VA, carries
principal visual axis
a) Secondary
• - Other retinal elements, secondary
visual axis
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21. Retinal Correspondence
• Retinal correspondence is the term
used when a viewed target
stimulates paired retinal areas in an
individual’s 2 eyes. These retinal
locations are said to be
corresponding.
• When the image of an object in
space falls on corresponding points,
it is perceived as a single object
located in the same subjective or
egocentric direction.

22. Egocentric localisation
• Perception of the location of an object in space with respect to either the eye
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23. Horopter
• The horopter is defined
as the locus of all points
in space that stimulate
corresponding retinal
points
• Double vision would be
expected when the
target does not lie on the
horopter
• Horizon of vision

24. Pannums Fusional Area
• The visual system can combine slightly
disparate points within a limited area
surrounding the horopter, called Panum’s area
of single binocular vision
• Objects within Panum’s area do not result in
diplopia.
• Objects outside Panum’s area stimulate widely
disparate retinal points, resulting in physiologic
diplopia

26. Anomalies of BSV
• When a manifest deviation of the eyes occurs, the corresponding retinal
elements of the eyes are no longer directed at the same object.
• This places the patient at risk for 2 distinct visual phenomena: visual
confusion and diplopia.

27. Sensory Adaptations in Strabismus
• To avoid visual confusion and diplopia, the visual system uses the
mechanisms of suppression and anomalous retinal correspondence.
• Pathologic suppression and anomalous retinal correspondence develop
only in the immature visual system under binocular conditions.

29. Suppression
• Suppression is the alteration of visual sensation that occurs when an eye’s
retinal image is prevented from reaching consciousness during binocular
visual activity
• Can be classified as such
- Central vs peripheral
- Non alternating vs alternating
- Facultative vs constant

30. Anomalous Retinal Correspondence
• Anomalous retinal correspondence (ARC) is a cortical adaptation that
restores some degree of binocular cooperation despite a (usually small)
manifest strabismus.
• In ARC, an object projects to the fovea of the fixating eye and to a
pseudofovea in the deviating eye without diplopia.
• Anomalous binocular vision is a functional state that is superior to total
suppression.
• The period during which ARC may develop probably extends through the
first decade of life.

31. Classification of ARC
Angle of Anomaly =
Objective Angle - Subjective Angle
Harmonious ARC
This indicates that the
• ARC fully corresponds to the
strabismus.
• provides a compensation for the
angle of squint
• Eliminate the awareness of
diplopia and confusion

32. Unharmonious ARC
- angle of anomaly < objective angle of deviation
- subjective angle # 0
Paradoxical
- when the angle of anomaly > objective angle of deviation.
- It occurs mainly after overcorrection of the squint surgery

33. Investigations
Test for fusion
- Bagollini striated glass test
- Worth 4 dots test
Test for stereopsis
- TNO test
- Frisby test
- Lang’s stereo test
- Synaptophore

34. WORTH FOUR-DOT TEST
This is a dissociation test which can be used with both distance and near
fixation, and differentiates between BSV, or ARC and suppression .
Procedure:
- The patient wears a green lens in front of the left eye
- And a red lens in front of the right eye
- The patient then views a box with four lights ; one red , two green and one
white

35.  If BSV is present all four lights are seen.
 If all four lights are seen in the presence of a manifest deviation, harmonious
ARC is present.
 If two red lights are seen , left suppression is present .
 If three green lights are seen , right suppression is present.
 If two red and three green lights are seen , diplopia is present.
 If the green and red lights alternate , alternating suppression is present.
Results

37. This is a test for detecting BSV , ARC or suppression . Each lens have fine
striations which convert a point source of light into a line, as with the
Maddox rod .
Procedure:
- The two lenses are placed at 45°and 135° in front of each eye and the
patient fixates a small light source .
- Each eye perceives an oblique line of light , perpendicular to that
perceived by the fellow eye.
- Dissimilar images are thus presented to each eye under binocular
viewing conditions .
BAGOLINI STRIATED GLASSES

39.  If the two streaks intersect at their centers in the form of an oblique cross ( an
X ), the patient has BSV if the eyes are straight , or harmonious ARC in the
presence of manifest strabismus .
 If the two lines are seen but they do not form a cross , diplopia is present .
 If only one streak is seen , there is no simultaneous perception and
suppression is present .
 If a small gap is seen in one of the streaks , a central suppression
scotoma ( as found in microtropia ) is present .
Results:

41. TNO test
● A booklet consisting of 7 plates
● Viewed with red- green spectacles
● Each plates contain various shape (squares, dots, crosses)
created by computer generated random dot analgyphs
● Analgyphs is a stereogram in which two disparate views are
printed in red and green on white background
● The eye looking through the red filter sees only green picture
as black
● The eye looking through the green filter sees the red picture
as black
● Two views fuse to give a stereoscopic effect
● 480- 15 sec of arc
● No monocular clues
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43. Frisby test
● Assess fine stereopsis
● Degree of disparity ranges from 600 to 15 seconds of
• arc
● Stereogram consists of 3 plates each containing 4 squares of small
random shape
● The three plates are of differing thickness, 6mm, 3mm and
• 1.5mm (55, 170, 340sec of arc , 40cm viewing distance)
● By adjusting the viewing distance, the test can give a disparity
of 600 to 15 sec of arc
● One of the squares contain one hidden circle which is seen disparately.
● Doesn’t require use of polarized glasses
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44. Titmus test
1) WIRT FLYTEST
• Assess gross stereopsis
• Utilizes the principle of vectograph
• Useful in young children
• Made up by 2 plates in the form of booklet
• The plates are reviewed with polaroid glasses
• The right side of booklet – large housefly with threshold 3000 sec of arc
• Stereoscopic ,will reach above the plate (child is encouraged to pick up the
tip of the wings between finger and thumb).
• Performed at a distance of 16 inches (40cm)
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45. 2) Animal test
● Assess fine stereopsis
● 3 rows of 5 animals each
● 1 animal from each row is imaged disparately (appear
forward).
● In each row, one of the animals imaged in two eyes is
printed heavily (misleading clue)
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46. 3) Circles test
● Consist of 9 squares
● Each containing 4 circles arranged in the form of a lozenge
● Only 1 of the circle in each square is
• disparately imaged at random
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48. Lang stereotest
• Targets are made up of fine vertical lines which are seen
alternatively by each eye when focused through built in
cylindrical lens elements
• Lang I: Disparity = Car 550", Star 600", Cat 1200"
• Lang II: Disparity = Moon 200", Car 400", Elephant 600", Star
monocular visible
• Unique feature – No polaroid glasses need to be worn for
viewing the test plate
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49. Synopthore
• Synopthore compensates for the angle of
squint and allows stimuli to be presented to
both eyes simultaneously
• Used to investigate the potential for binocular
functions in the presence of manifest squint
and useful in assessing young children
• It can detect suppression and ARC
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50. Two pencil test
• Gross stereopsis
• Examiner holds the pencil vertically in front of patients eye
• Patient touch the upper tip of pencil
• Having stereopsis – Pass test with BE open
• One eye closed – patient fails the test
• Disparity range : 3000-5000 secs of arc
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51. Conclusion
• BSV is not inborn,but develops in the first decade of life
• Abnormal visual experience results in poor or no BSV
• Reversible only if intervened in the plastic period of
development
• A good understanding of mechanism of BSV is
fundamental in successive treatment of its anamolies

52. References
Reference
• Adler’s physiology of eye: clinical application, 10th Ed. St
Louis: Mosby, 2003.
• Khurana A. K.: Theory and Practise of Squint and Orthoptics;
first ed
• AAO Pediatric Ophthalmology and strabismus 2022- 2023

53. MCQ 1
1. Requirements for Binocular Single Vision include
a. Normal retinal correspondence
b. Good vision in one eye
c. Precise coordination of the eyes at all times
d. Ability of fusional areas of brain to fuse slightly dissimilar images
e. Normal macular function

54. MCQ 1
1. Requirements for Binocular Single Vision include
a. Normal retinal correspondence T
b. Good vision in one eye F
c. Precise coordination of the eyes at all times T
d. Ability of fusional areas of brain to fuse slightly dissimilar images T
e. Normal macular function T

55. MCQ 2
In Binocular vision
a. Only points on the horopter fall on the corresponding retinal points
b. Points in front of the horopter will stimulate binasal retina
c. Points outside the horopter is perceived doubly
d. The Pannum’s fusional area is wider in the centre than periphery
e. Sensory fusion refers to the cortical integration of images perceived
by the two eyes

56. MCQ 2
In Binocular vision
a. Only points on the horopter fall on the corresponding retinal points T
b. Points in front of the horopter will stimulate binasal retina F
c. Points outside the horopter is perceived doubly T
d. The Pannum’s fusional area is wider in the centre than periphery F
e. Sensory fusion refers to the cortical integration of images perceived by
the two eyes T

57. MCQ 3
Advantages of binocular single vision include
a. A larger field of vision
b. Elimination of blind spot
c. Better binocular visual acuity
d. Accurate depth perception
e. Multiple mental impression

58. MCQ 3
Advantages of binocular single vision include
a. A larger field of vision T
b. Elimination of blind spot T
c. Better binocular visual acuity T
d. Accurate depth perception T
e. Multiple mental impression F

59. THANK YOU