for residents and ophthalmologists

1. Binocular Vision
By Dr.Desta G.(R-1)
Moderator Dr.Addisu (Assistant
Prof. of Ophalmology, AAU,CHS)
June/2018

2. Seminar outline
Introduction
Development of binocular vision
 theories of binocular vision
Clinical investigations of binocular vision

3. Defn.
• “It is vision in which the images from the two
eyes are used together”
• “a series of sensory and motor processes that
culminate in the perception of singleness and
stereoscopic depth”

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

5. 1. Simultaneous perception
• “Power to see 2 dissimilar
objects simultaneously”
• Ceases only when we
suppress the image from
one eye at will.

6. 2. 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.

7. 3. 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

8. Pre-requisites for BSV
Motor mechanism:
• Correct neuromuscular development so that the visual
axes are directed at the object.
• Overlap of visual fields.
Sensory mechanism:
• Approximately equal image clarity and size in the two eyes.
• Corresponding retinal areas so that the eyes are cyclopean
• Normal visual pathway
Mental Process:
• Ability of visual cortex to promote binocular single vision.
Tuesday, January 22, 2019

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

11. MILESTONES
• At birth : no bifoveal fixation.
• 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
• 3-6mts : conjugate movements and disjugate vergence movements.
• 1yr : fusional movements are firmly established.
• 2-3yrs : adult level of visual acuity is reached
• 6 yrs ; adult level of stereoacuity is reached

12. 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.

14. NEUROPHYSIOLOGY OF
DEVELOPMENT cont…
• Fundamental anatomic base for BV is
anatomic partial decussation of at optic
chiasm
• Receptive field at the cortical neuron
• At birth retina and optic pathway not
completely developed but basic receptive field
organization of neurons and cortical
architecture are present

15. NEUROPHYSIOLOGY OF
DEVELOPMENT cont…
• Neurons in the visual cortex are markedly
influenced by visual experience during the
first few post natal months
• Neural properties involve
1) Ocular dominance
2) Orientation specificity
3) Binocularity
4) Disparity specificity

16. NEUROPHYSIOLOGY OF
DEVELOPMENT cont…
• Simultaneous occurrence of patterned visual
input necessary to binocular vision devt.
• Monocular deprivation could affect BV up to
2years.

17. Normal binocular development
• Four main indices of binocularity have been used
1) Accuracy of alignment of the visual axis of the
two eyes
2) Looking preference for binocular desparity
containing simuli over flat stimuli
3) Binocular facilitation of VEP for Binocular
stimulation
4) VEP response in binocular disparity in random
dot stimuli

18. • 50% new borns have
exotropia. It corrects
around 2nd month
• Both preferential
looking studies and VEP
studies suggest earliest
evidence of stereopsis
occurs at 3rd month
• stereo acuity reaches
adult level at 6 years of
age

19. NEUROPHYSIOLOGY OF
DEVELOPMENT cont…
• Binocular VEP = Monocular VEP at birth.
• Binocular summation: Increase in amplitude
of VEP for binocular relative to monocular.
• Full BS means doubling of the monocular
amplitude
• Binocular facilitation when amplitude is more
than full BS. At 3 months
• Adult level is FBS 12 months.

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

21. OCULOCENTRIC
(MONOCULAR)
• 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
• Each point on retina can have
its own visual axis
• Therefore, for a given eye
position , objects having
superimposed retinal images
will be seen in a line but at
different distances

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

23. RETINAL
CORRESPONDENCE
• Binocular retinal
correspondence is defined
by the set of retinal image
locations that produces
perceptions of identical visual
directions when viewing with
one eye, or with the other, or
with both eyes simultaneously
 Normal vs Anomalous
“Correspondence, normal or
anomalous, is necessary for
single binocular vision.”

24. Types
Normal Retinal Correspondence:
• Retinal correspondence is
called normal when both the
fovea have a
• common visual direction and
the retinal elements nasal to
the fovea
• in one eye corresponds to the
retinal elements temporal to
the fovea in the other eye.
.
Abnormal Retinal
Correspondence:
• Retinal correspondence is
abnormal when the fovea of
one eye has a common visual
direction with an extra foveal
area in the other eye.
• This is generally seen if the
angle of squint is small and the
• extrafoveal point is close to
the fovea. It is an attempt to
regain the
• binocular advantage

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

26. VIETH-MÜLLER
CIRCLE
• Theoretical or mathematical
horopter curve
• 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

27. 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

28. 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

29. 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.

30. 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

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

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

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

35. 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
All are absolute contemporarily

36. PHYSIOLOGICAL BASIS
OF FUSION
• PHYSIOLOGICAL BASIS OF FUSION
• 4 classes of neurons identified by HUBEL &
WIESEL
① Binocular Corresponding
② Binocular Disperate
③ Monocular Right
④ Monocular left

38. DICHOPTIC
STIMULATION
l. 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

39. DICHOPTIC
STIMULATION cont…
• Images that are very different at corresponding
retinal locations in the two eyes provide
dichoptic stimulation conditions.
• Possible outcomes are
1) Binocular rivalry
2) Inter-ocular suppression
3) Binocular summation
• NB images of high contrast can give binocular
summation if they are presented for brief period
<150ms

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

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

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

44. • 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.

45. PHYSIOLOGICAL BASIS OF
STEREOPSIS
• Stereopsis a function of spatial disparity
• Local and global stereopsis
• Fine v/s coarse stereopsis
• Stereopsis and fusion

46. 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

47. 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

48. 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

51. INVESTIGATIONS FOR BINOCULAR
VISION
• All the BSV tests are
aimed at assessing the
presence or absence of:
 Normal or abnormal
retinal correspondence
 Suppression
 Simultaneous
perception
 Fusion
 Stereopsis

52. Before any test is undertaken it is essential to
assess the:
• visual acuity
• fixation in the squinting eye
• direction and size of deviation

53. TEST FOR RETINAL CORRESPONDENCE
• Bagolini's striated glasses test
• Worth's 4 dot test
• After image test
• Red filter test

54. TEST FOR SUPPRESSION
• Bagolini’s striated glasses
• Worth's four dot test
• 4 Δ prism base out test
• Red filter test

55. TESTS FOR FUSION:
• Worth’s 4-dot test
• Bagolini’s striated glasses

56. TESTS FOR STEREOPSIS
Qualitative tests for Stereopsis:
• Lang’s 2 pencil test
• Synaptophore
Quantitative tests for Stereopsis:
• Random dot test
• TNO Test
• Lang’s stereo test
• Titmus stereo test

57. 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 .
• Results can only be interpreted if the presence or absence
of a manifest squint is known at time of testing.
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 .

59. • 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.

64. BAGOLINI STRIATED GLASSES
• 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
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 .

65. Results
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 independent 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 .

67. AFTER IMAGE TEST
• This test is performed on Synoptophore
• RE is stimulated with an illuminated vertical
line for 10 - 15 sec.
& the patient is asked to see at its center
• Then the LE is stimulated with an illuminated
horizontal line for 10 - 15 sec.
• The patient is asked to close his eyes & open
the eyes after a few sec. then look at the wall.

68. RESULTS:
• In NRC the patient will see the perfect cross
• In ARC with ET he will see the horizontal line
in front of RE & vertical line in front of LE
• ARC with XT he will see the vertical line in
front of RE & horizontal line in front of LE

69. RED FILTER TEST
• This test is applied to reveal diplopia.
Procedure:
• The red glass is placed in front of patient’s one eye & a
light is projected to the eyes of the patient. He/ she is
asked to see at the light source.
Results:
• In case of orthophoria he will see a single red light.
• In case of Esotropia he will see 1 red & 1yellow light.
Diplopia will be uncrossed.
• In case of Exotropia he will see 1 red & 1 yellow light.
Diplopia will be crossed

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79. Quantitative tests for Stereopsis
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81. Reference
 Gunter K. von Noorden: Binocular Vision and
Ocular Motility, Theory and Management of
strabismus, Sixth ed,2.
 Binocular Vision Anomalies Pickell’s 5th Edition.
 Binocular Vision by Rahul Bhola, MD PDF
 ADLER’S Physiology of the eye
 Duanes clinical ophtalmology 2012
 Online sources
Tuesday, January 22, 2019