binocular single vision

1. S
BINOCULAR SINGLE
VISION
Presented by: Dr. Shrey Maheshwari

2. DEFINITION
 Acc. to ROMANO & ROMANO
 State of simultaneous vision with two seeing eyes
that occurs when an individual fixes his visual
attention on an object of regard.

3. GRADES OF BINOCULAR
VISION
1. Simultaneous perception
2. Fusion
3. Stereopsis

4. SIMULTANEOUS
PERCEPTION
S Does not imply that both eyes see same object.
S 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.

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

8. STEREOPSIS
S 3rd Grade of Binocular Vision
S Visual appreciation of three dimensions
S Ability to obtain impression of depth by superimposition of
two images of the same object, seen from 2 slightly
different angle.
Not similar to depth perception.

9. 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.

10. PHYLOGENETIC
BACKGROUND AND
EVOLUTION
Present only in higher animals.
 Frontally placed eyes
 Binocular co-ordination of eye movements
 Semidecussation of optic tract

11. PSYCHOPHYSICS AND
SENSORY ASPECTS
1. Visual direction and horopter
2. Binocular fusion
3. Dichoptic stimulation
4. Stereopsis
5. Depth perception
6. Integration of motor and sensory systems

12. VISUAL DIRECTION AND
HOROPTER
S Location of an object is its Physical space.
The (objective) lines of direction determine which retinal area will be
stimulated
S Localisation of an object is its Visual/ Subjective
space.
The (subjective) counterpart, the visual directions, determine the
direction in
which the object will be seen in visual space.

13. Discrepancies of Objective
and Subjective Metrics
S Hering’s experiment.
S Kundt and Münsterberg experiment.

14. HERING’S EXPT.
 Demonstrated that objects that may be widely separated
in physical space may have a common direction in
subjective space.
 Anatomic distribution of retinal elements and
physiological distributuion of spatial values do not
coincide
 Demonstrated that spatial values of retinal receptors
defer above and below horizontal midline

15. HERING’S EXPT.

16. KUNDT AND
MÜNSTERBERG
EXPERIMENT
S If one attempts to bisect a monocularly fixated line in an
arrangement that excludes other visual clues from the field, a
constant error is detected.
S If placed horizontally, the line segment imaged on the nasal
side of the retina, that is, the one appearing in the temporal half
of the field, is larger than the temporally imaged retinonasal line
segment.
S In general, the discrepancies in the two eyes are symmetrical.
They compensate each other, and the partition of a line into two
equal segments is more nearly correct in binocular fixation.

17. VISUAL DIRECTIONS
S OCULOCENTRIC (MONOCULAR)
S EGOCENTRIC (BINOCULAR)

18. OCULOCENTRIC
(MONOCULAR)
S When an object is viewed, its image falls on the foveola. The
visual direction is represented by a line joining the two points,
known as the principle visual line or axis
S Each point on retina can have its own visual axis
S Therefore, for a given eye position , objects having superimposed
retinal images will be seen in a line but at different distances

19. EGOCENTRIC
(BINOCULAR)
S Frame of reference is head (egocentric) not eyes.
S Visual space is seen with imaginary single eye(cyclopean
eye)
S Herring’s law of identical visual direction – foveae have a
common subjective visual direction.

20. CYCLOPEAN EYE

21. RETINAL
CORRESPONDENCE
S Fovea determines the principle visual direction.
S Both fovea has same space value i.e. ‘ZERO’
S Each receptor under monocular condition dictates visual
direction in relation to fovea.
S Images falling on corresponding locations in each eye creates
single mental impression.
S Acc. To BAGOLINI it’s area to area relationship not point to point
relationship

22. 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

23. 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

24. EMPIRICAL HOROPTER
CURVE
• Hering and his pupil 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

25. HOROPTER CURVE

26. PHYSIOLOGIC
DIPLOPIA
 All points on the horopter curve are seen singly
 Diplopia elicited by object points off the horopter is called
physiologic diplopia.

27. PHYSIOLOGIC
DIPLOPIA
S When fixating a distant object, a nearer object is seen in
crossed (heteronymous) diplopia.
S When fixating a near object, a distant object is seen
in uncrossed (homonymous) diplopia.

28. PHYSIOLOGIC
DIPLOPIA
CROSSED DIPLOPIA UNCROSSED DIPLOPIA

29. CLINICAL SIGNIFICANCE
 In diagnosing binocular cooperation
 In orthoptic treatment of comitant strabismus

30. BINOCULAR
FUSION
SENSORY FUSION
MOTOR FUSION
When images of an object fall on corresponding retinal
points, they seem fused into a single mental impression
• The ability to align the eyes in such a fashion that sensory fusion
can be maintained is Motor fusion.
• The stimulus for these fusional eye movements is retinal
disparity.
• It is the exclusive function of the extra foveal retinal periphery

31. 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

32. PANUM’S 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)
• If the fixation distance is 20m, objects behind the
horopter always appear single since the
disparity of their images is always smaller than
panum’s area.

33. PANUM’S AREA

34. FIXATION DISPARITY
 Ogle and coworkers coined this term.
 A physiologic variant of normal binocular vision exists when a
minute image displacement, rarely exceeding several minutes
of arc of angle, occurs within Panum’s area while fusion is
maintained.
 May arise from small foveal scotoma or oculomotor imbalance
used to measure the accommodative convergence–
accommodation (AC/A) ratio

35. FIXATION DISPARITY

36. THEORIES OF BINOCULAR
FUSION
4 Different Theories
1. Synergy hypothesis of panum
2. Local sign hypothesis of hering
3. Eye movement hypothesis of helmholtz
4. Suppression hypothesis of du tour and verhoff
O
B
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O
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E
T
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37. PHYSIOLOGICAL BASIS
OF FUSION
 4 classes of neurons identified by HUBEL & WIESEL
① Binocular Corresponding
② Binocular Desperate
③ Monocular Right
④ Monocular left

38. PHYSIOLOGICAL BASIS OF
FUSION

39. DICHOPTIC
STIMULATION
 Different stimulation in two eyes when binocular stimuli fall on non-
corresponding points of the two retinae. 5 classes of percepts are obtained :-
a) Depth with fusion
b) Depth with diplopia
c) Diplopia without depth
d) Binocular rivalry and suppression
e) Binocular lustre

40. DIPLOPIA WITHOUT DEPTH
S Diplopia can be crossed or uncrossed
S Sensory adaptation to reduce diplopia :-
a. Supression
b. Amblyopia
c. Abnormal Retinal Correspondence
 Motor adaptation to reduce diplopia :-
a. Abnormal head posture
b. EOM changes

41. RETINAL RIVALRY AND
SUPPRESSION
S 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
S Response – Suppression (innate involuntary process) whereby the signals
coming from certain retinal elements are ignored in favor of those
coming from another part
S 1st line of defense in against pathological interruption; e.g. Marked
refractive error in one eye, strabismus.

42. RETINAL RIVALRY AND
SUPPRESSION

43. STEREOPSIS
S Wheatstone invented stereoscope in 1838
S Visual appreciation of three dimensions during binocular
vision, occurring through fusion of signals from disparate
retinal elements.
S Vertical displacement produces no stereoscopic effect.

44. STEREOPSIS
S A solid object placed in the median plane of the head
produces unequal images in the two eyes.
S The sensory fusion of the two unequal retinal images
results in a three-dimensional percept.
S A stereoscopic effect can also be produced by two-
dimensional pictures

45. STEREOPSIS

46. STEREOPSIS
o An object placed in front of fixation, but within panum’s
fusional space will stimulate disparate retinal elements.
o Each image will be temporal to the point corresponding
to location of image in the other eye.
o Although both images are fused, the perception has the
added quality of nearness relative to the fixation point.
o Conversely an object behind the fixation point will cause
nasal disparity and give the perception of farness.

47. STEREOPSIS
 Stereopsis is a unique cognition, a distinct perceptional
quality.
 If one does not have it, one cannot learn it even in the
presence of all requirements such as bifoveal fixation,
fusion, and good visual acuity.
 It is all or none phenomenon
 Beyond 600mts there is no true stereopsis. At this
distance monocular clues take over for the perception of
depth.

48. PHYSIOLOGICAL BASIS OF
STEREOPSIS
o Stereopsis a fucntion of spatial disparity
o Local and global stereopsis
o Fine v/s coarse stereopsis
o Stereopsis and fusion

49. DEPTH PERCEPTION
• 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

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

51. 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

52. LINEAR PERSPECTIVE OVERLAY OF CONTOURS

53. DISTANCE FROM HORIZON DISTRIBUTION of HIGHLIGHTS AND SHADOWS

54. DEVELOPMENT OF
BINOCULAR VISION
S Basic visual functions are innate and therefore
present at birth.
S Their coordination, maturation and refinement
take place during early postnatal period.

55. MILESTONES
 At birth : no bifoveal fixation.
 Monocular fixation is present at birth, but poor.
 2-3wks : infant begins to make movements of regard, turning his eyes to fixate an
object
 4-5wks : can sustain monocular fixation of large near objects
 6wks : fixation alternates rapidly b/w 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.
 3-6mts : conjugate movements and disjugate vergence movements.
 1yr : fusional movements are firmly established.
 2-3yrs : adult level of visual acuity is reached.

56. 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 foveae
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.

57. NEUROPHYSIOLOGY OF
DEVELOPMENT
 2 different visual pathways from different population of retinal
ganglion cells.
 Parvo and Magno cells- in lateral geniculate body.
 P cells- colour, fine 2 point discrimination (what) and project to the
areas of fovea
 M cells- direction, motion, speed, flicker, gross binocular
disparities(where). 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.

58. BINOCULAR VISION TESTS
1. Simultaneous perception
2. Fusion
3. Stereopsis
Most useful instrument for the testing is the
Synaptophore.

59. SIMULTANEOUS PERCEPTIO

60. FUSION

61. TEST FOR
STEREOPSIS
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

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

63. 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

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

65. ANIMAL TEST
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 .

66. ANIMAL & FLY TEST

67. CIRCLE TEST
 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.

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

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

71. LANG TEST

72. TNO RANDOM DOT
TEST
 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

74. MOTOR TESTS

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

76. TWO PENCIL TEST

77. THANK YOU