basics of binocular vision

1. 1
BINOCULAR VISION
Presenter- Dr Saransh Jain

2. DEFINITION
NORMAL BINOCULAR VISION
DEVELOPMENT OF BINOCULAR VISION
THEORIES OF BINOCULAR VISION
MECHANISM OF BINOCULAR VISION
GRADES OF BINOCULAR VISION
ABNORMALITIES OF BSV
CLINICAL TESTS FOR BSV
TO THE SEMINAR

3. DEFINITION
• 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.

4. 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

5. Why to study binocular vision?
• The basic laws of binocular vision forms the very
foundation on which our current understanding of
strabismus and its symptoms and sensory
consequences is based.
• Knowledge on BSV forms basis to orthoptic
treatments & many physiological processes in the eye.

6. DEVELOPMENT OF BINOCULAR
VISION
2 to 3 weeks turning head to fixate an object
4 to 5 weeks sustain monocular fixation of large near objects
3 months binocular fusion
3 to 6 months stereopsis
1 YR Fusional movements firmly established
2-3 yr Adult level visual acuity reached

7. 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

8. 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.

9. NEUROPHYSIOLOGY OF
DEVELOPMENT
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.

10. MECHANISM OF BINOCULAR
VISION
• Visual axis
• Retinal correspondence
• Egocentric localisation
• Horopter
• Pannums fusional area

11. VISUAL AXIS

12. VISUAL DIRECTIONS
• OCULOCENTRIC (MONOCULAR)
• EGOCENTRIC (BINOCULAR)

13. OCULOCENTRIC
(MONOCULAR)
• 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)

14. EGOCENTRIC (BINOCULAR)
• 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.

15. RETINAL CORRESPONDENCE
• Correspondence- relative localisation of objects in space to each
other under binocular conditions.
• Fovea determines the principle visual direction
• Both fovea has same space value i.e. ‘ZERO’ (principal VD)
• Each receptor under monocular condition dictates visual
direction in relation to fovea
• Images falling on corresponding locations in each eye creates
single mental impression.
• Acc. To BAGOLINI it’s area to area relationship not point to point
relationship

16. HOROPTER
• Introduced in 1613 by Aguilonius
• Approached mathematically by Helmholt
• Means ‘Horizon of vision’
• Locus of all object points that are imaged on corresponding
retinal elements at a given fixation distance.
• Different horopter for each fixation distance

17. VIETH-MÜLLER CIRCLE
o Theoretical or mathematical horopter curve
o If corresponding points have a geometrically
regular horizontal distance from the two retinas,
the longitudinal horopter curve would be a circle
passing through the center of rotation of the two
eyes and the fixation point

18. EMPIRICAL HOROPTER CURVE
• Hering and Hillebrand could show that the Vieth-
Müller circle does not describe the longitudinal
horopter.
• Empirical horopter curve is flatter than the Vieth-
MÜller circle
• Distribution of the elements that correspond to each
other is not the same in the nasal and temporal parts
of the two retinas

19. HOROPTER CURVE

20. PANUM’S AREA
• Panum, the Danish physiologist, first reported this
phenomenon.
• Region in front and back of the horopter in which
single vision is present is known as Panum’s area of
single binocular vision or Panum’s fusional area
• Horizontal extent of these areas is small at the
center (6 to 10 minutes near the fovea)
• Increases toward the periphery (around 30 to 40
minutes at 12° from the fovea)

21. PANNUMS FUSIONAL AREA

22. 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

23. 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

24. GRADES OF BINOCULAR VISION
• SIMULTANEOUS PERCEPTION
• FUSION
• STEREOPSIS

25. 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.
• Does not imply that both eyes see same object.
• Does not imply superimposition of both objects.
“Power to see 2 dissimilar objects simultaneously”
 Ceases only when we suppress the image from one
eye at will.

26. FUSION
• 2nd Grade of Binocular Vision
• Ability of the eyes to produce a composite picture
from two similar pictures, each of which is
incomplete in a small detail.
• It is not superimposition of dissimilar pictures

27. 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
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.

28. STEREOPSIS
• 3rd Grade of Binocular Vision
• Visual appreciation of three dimensions
• Ability to obtain impression of depth by superimposition of
two images of the same object, seen from 2 slightly different
angle.
• Retinal disparity (Fixation disparity) is the basis of 3 D
perception
• Stereopsis occurs when Retinal disparity is not large enough
for simple fusion but small enough to cause diplopia
Not similar to depth perception.

29. ADVANTAGES
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.

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

31. Monocular./Non Stereoscopic
Clues
a) Parallactic movements
b) Linear perspective
c) Overlay of contours
d) Size
e) Distance from horizon
f) Distribution of highlights & shadows
g) Aerial perspective

32. PARALLACTIC
MOVEMENTS
 Most important in depth perception next to stereopsis
 Slight shift of head while fixation is maintained results
in change of relative position of objects in gaze
 Objects beyond fixation point – move in same direction
 Objects closer – move in opposite direction

33. LINEAR PERSPECTIVE OVERLAY OF CONTOURS

34. DISTANCE FROM HORIZON DISTRIBUTION of HIGHLIGHTS AND SHADOWS

35. Advantage of having BSV
• Stereopsis
• Binocular summation.
– vision shaper, clearer &
more sensitive
• Larger field of view.
• Spare eye
visual field

36. Abnormal binocular vision
Confusion
Diplopia
Suppresion
Eccentric fixation
Abnormal retinal correspondence(ARC)
Amblyopia

37. 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.

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

39. CLINICAL TESTS
• For retinal correspondence
• For supression
1.Red filter test
2.Worth FDT
3.Bagolinis striate glass test
4.After image testing

40. • Tests for stereopsis
Qualitative
Random dot stereograms
Synaptophore
Quantitative
Titmus fly test
TNO test
Lang test

41. WFDT
MONOFIXATION SYNDROME

42. BAGOLINIS GLASS TEST

43. AFTER IMAGE TESTING

44. Stereopsis testing
• Stereo acuity is a quantitative measure of stereopsis, it
represents the smallest horizontal retinal image
disparity that give rise to a sensation of depth.
• Stereopsis is measured in seconds of arc.
• 1degree=60minutes of arc, 1minute=60seconds of arc.
• Normal stereoacuity= <60seconds of arc.

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

46. VECTOGRAPH TEST - TITMUS
STEREO TEST
 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

47. ANIMAL & FLY TEST

49. TNO RANDOM DOT
TEST