Binocular single vision allows for the blending of separate images from each eye into a composite image. It requires overlapping visual fields between the eyes, intact neural pathways, and corresponding retinal areas. The advantages of binocular vision include wider field of view, better detection of faint images, stereopsis for depth perception, and improved visual acuity. Abnormal retinal correspondence can allow limited binocular vision by pairing the fovea of one eye with a non-foveal point in the other eye.

1. Binocular Single Vision

2. Binocular Single Vision
 Binocular single vision is the state of
simultaneous vision with the two
seeing eyes and blending of the
separate images seen by each eye
into one composite image.

3. Requirements for BSV
 Overlapping of visual field
 Approximately same image quality
and size in both of the eyes
 Intact retinal neural system
 Accurate neuromuscular development
and coordination so that visual axes
are directed at the same object

4.  Normal visual pathways
 Corresponding retinal areas (so that eyes
are cyclopean.)
 Partial decussation of the optic nerves
at optic chiasma to bring the retinal
information from corresponding areas
of each eye together at the visual
cortex

5. Advantages of Binocular vision:
1. Second eye could be a safety factor against injury or
disease
2. Two eyes may be used to achieve the wider field of
view
3. Where the field of the two eyes overlap ,there is an
advantage
*In detection of faint images
*Rejection of optical distortions.
4. Stereopsis – the most precise kind of depth
perception
5. Summation of visual acuity (improved VA with both
eyes open)

6. Visual Direction
The projection of a given retinal element in a specific direction in
subjective space. It is the line of sight.
Principal visual direction is the direction in external space
interpreted as the line of sight. This is normally the visual direction of
fovea and is associated with a sense of direct viewing.
Secondary visual directions are the projecting directions of
extrafoveal points with respect to the principal direction of the fovea,
associated with indirect viewing.)
Projection
Is the subjective interpretation of the position of an object in
space on the basis of stimulated retinal elements. The
localization of an object in space.

7. Corresponding points;
Corresponding points are areas on retina that share the same
subjective visual direction.
 Fovea of both eyes are corresponding points.
 Points on nasal retina of one eye have a correspondance with
the temporal retina of other eye.
The image of an object in the peripheral visual field falls on the
extrafoveal element.
To establish fixation on that object an eye movement of accurate
amplitude is required.
Each extrafoveal retinal element, therefore has a retinomotor
value proportional to its distance from fovea.

10.  The fovea normally has a retinal motor value of zero.
 A relationship exists between the cells in the retina of each
eye. In order to understand this relationship, we arbitrarily
assign retino-motor values to retinal areas.
 These areas or elements in each eye that share a same
subjective visual direction (eg. +1 nasal RE, +1 temporal LE)
are corresponding retinal points
F
+1
-1
F
+1
-1

11. Abnormal retinal
correspondance;
 It is a condition in which non-
corresponding retinal points acquire a
common visual direction.
 The fovea of fixating eye is paired with
the non foveal element of the deviated
eye.
 ARC allows limited amount of
binocular vision.

12. Horopter
 it is an imaginary plane in space, all points
on which stimulate corresponding retinal
elements and therefore are seen singly.

14. Pannum’s Fusional Area
 It is a zone in front of and behind the
horopter in which subjects not
accurately stimulate corresponding
retinal points. Objects are seen singly
and stereoscopically.
Physiological Diplopia
 Objects outside Pannum’s fusional
area appear double.

15. Simultaneous Perception
Fusion
Stereopsis
Grades of BSV

16. Simultaneous Perception
 Grade I: Simultaneous perception
occurs when the visual cortex
perceives separate stimuli of the two
eyes at the same time.

17. Fusion
 Grade II: It represents true fusion with
some amplitude. It is the ability of
producing a composite picture of two
similar objects.

18. Stereopsis
 Grade III; perception of relative depth of
objects, three dimensional.
It arises when objects are behind and in front of
the point of fixation but within the Pannum’s
fusional area stimulate horizontally disparate
retinal points simultaneously.
It results in sensation of solid objects. It is
measured in seconds of arc.

19. Abnormalities of BSV
 Confusion
Is the simultaneous appreciation of
two superimposed but dissimilar
images caused by stimulation of
corresponding retinal points by images
of different objects.
As the eyes are misaligned dissimilar
image fall on corresponding retinal
points causing visual confusion.

20.  Pathological Diplopia;
Pathological diplopia is the simultaneous
appreciation of two images of the same object. It
results from image of same object falling on non
corresponding points.