Binocular single vision along with grading and abnormalities

2.  Visual development is a highly complex
maturation process. Structural changes
occur in both the eye and the central
nervous system.
Normal vision develops as a result of
genetic coding and experience in a
normal visual environment.

3. Binocular single vision (BSV) development
occurs together with improving monocular
vision.

4. Binocular cells are present from birth on,
but they need the input from both eyes in
order to become binocularly driven.
Refinement of neuroanatomic connections
and the development of normal binocular
vision are dependent on appropriate
binocular visual stimulation.

5.  Binocular Vision is the coordinated use of both
eyes to create one three-dimensional single
visual sensation.
 It is being made possible through the
senso-motoric union of the eye.

6.  Full visual acuity on both eyes with normal
central fixation
 Optical system of the two eyes have to be the
same
 Normal retinal correspondence
 Visual fields have to overlap each other
 Normal functioning of the nerve centres and
the visual pathway
 Binocularly driven cells in the visual cortex
 Normal visual development

7.  Orthophoria or heterophoria
 Full extraocular movements of both eyeballs
 Proper coordination of accommodation and
convergence

9. left
eye
right
eye

10. left
eye
right
eye
thalamus
optic
chiasm
Greek letter
chi : 

11. left
eye
right
eye
visual
cortex
thalamus
optic
chiasm

12. thalamus
optic
chiasm
left visual
cortex;
right
visual
hemi-
field

13. right
visual
cortex;
left visual
hemifield
thalamus
optic
chiasm
left visual
cortex;
right
visual
hemi-
field

14. left side
of
thalamus
showing
visual area
(lateral
geniculate
nucleus)

15. left side
of
thalamus
showing
visual area
(lateral
geniculate
nucleus)
1
2
3
4
5
6

16. left side
of
thalamus
showing
visual area
(lateral
geniculate
nucleus)
inputs from
left eye
inputs from
right eye
1
2
3
4
5
6

17.  Visual direction
 Projection is the term for object location in space
and it depends on the point on the retina
being stimulated
 Each part of the retina has a given angle from
fixation
 This is termed the visual sign or visual
direction
 The fovea is the reference point
 The fovea has the principal visual direction
 All other points have secondary visual
direction

19. The perceived direction of the object is an
intrinsic part of the retinal elements.
 Fovea projects straight ahead
 Nasal retina projects temporally
 Temporal retina projects nasally
 Superior retina projects inferiorly
 Inferior retina projects superiorly

20.  Retinal corrospondence:
If retinal areas in the two eyes share a common
subjective visual direction they are said to be
corresponding.
 Normal Retinal corrospondence:
If corresponding retinal areas in both eyes bear
identical relationships to the fovea in each eye, then
normal retinal correspondence exists.

21.  Images falling on corresponding points are
seen singly
 Nasal retinal points in one eye correspond
to temporal points in the other eye
 Sight originates from a point central to both
eyes representing the cerebral
interpretation of the direction of an object

22.  Normal retinal correspondence is necessary
for BSV
 An object fixated by the two fovea appears
to be located centrally by a cyclopean eye
 Binocular projection can be considered as if
from this imaginary cyclopean single eye
 Cyclopean projection diagrams are always
used to describe BSV

23. T
F
N N
F
T
Right Eye
Left Eye

24.  Horopter:
 All points which are stimulating
corresponding retinal elements are lying on
an imaginary circle in space called horopter.

25.  Panum`s area :
 Tolerance space around the horopter where
objects are falling on slightly disparate retinal
areas but are still physiologically seen single
is called Panum’s area of single binocular
vision

26. Physiology of
Normal Binocular vision
Panum`s Area and
Horopter
TRE F NRE NRE F TRE
Nasal retinal
elements of
one eye are
working
together
with
temporal
retinal
elements of
the other
eye
The visual
direction
of the
fovea is
localized
„straight
ahead“-
An element right of the fovea
has the visual direction left
from straight ahead and vice
versa

29.  Visual information from the right half of both
retinas is transferred to the right half of the
brain and vice versa.
 Thus, visual information from both eyes is
available to the cortical cells which combine the
double information
into one image

30. ‘Simultaneous use of two eyes to
give one mental image.’

31. Simultan Perception
Fusion
Stereopsis

32. Simultan perception
 The ability to perceive two pictures at the same
time in each retina.
 Dissimilarly contoured images are only perceived
simultaneously by the extramacular portions of
the retina.

33. Fusion
Cortical unification of visual objects into one single
percept made possible by the stimulation of
corresponding retinal areas.

34.  Sensory fusion based on the relationship
between retina and visual cortex
 Motor fusion is the ability to maintain sensory
fusion through a range of fusional vergence
movements – „diplopia-avoidance mechanism“

35. Stereopsis
Response to disparate retinal stimulation
Ability to perceive objects three-dimensionally
Binocular sensation of relative depth caused by
horizontal retinal disparity which is not great
enough to provoke diplopia

37. THANK YOU