Binocular vision develops gradually in infants, from following light monocularly at 2-3 weeks to binocularly at 6 weeks to 6 months. By 6 months, accommodation has developed but lags behind convergence. Sensory fusion blends monocular images into a single image, while motor fusion maintains eye alignment. Binocular vision provides advantages like single vision, stereopsis, and an enlarged visual field. Normal binocular vision requires clear visual axes, sensory fusion, and motor fusion.

1. Binocular Vision, Fusion, and
Accommodation

2. Fusion Development in the Infant
 Birth – fixation reflex poor with random eye
movements
 2-3 weeks – follows light monocularly
 6 weeks to 6 months – follows light
binocularly
 4 weeks to 6 months – convergence
developing
 By 6 months – accommodation developing –
lags behind convergence

3. Fusion
 Sensory fusion – the cortical process of
blending the images from each eye into a
single binocular stereoscopic image
 Motor fusion – the mechanism that allows
fine-tuning of eye position to maintain eye
alignment – this is known as fusional
vergence

5.  Approximately 70% of the cells in the striate
cortex are binocular cells
 Retinal areas from each eye that project to
the same binocular cortical cells are called
corresponding retinal points.

7. Worth’s Three Degrees of Fusion
 Simultaneous perception
 Flat fusion
 Stereopsis

8. Simultaneous perception

9. Flat Fusion
 Worth Four Dot Test

10. Stereopsis
 Titmus Stereo Test

11. Binocular Single Vision
Separate and slightly dissimilar
images arising in each eye are
fused together as a single image.

12. Advantages of Binocular Vision
 Single Vision
 Stereopsis
 Enlargement of visual field
 Compensation for blind spot and other
differences in the field of vision

13. Normal Binocular Single Vision
Requirements
 Clear visual axis
 Sensory fusion
 Motor fusion

14. Sensory Obstacles
 Dioptric obstacles – refractive errors,
anisometropia
 Prolonged monocular activity – severe
ptosis, media opacities
 Retinoneural – lesions of retina, optic nerve
 Proprioceptive

15. Motor Obstacles
 Congenital craniofacial malformations
 Conditions affecting extraocular muscles
 CNS lesions – involving upper motor
neurons

16. The Perception of Depth
 Stereopsis
 Monocular clues to depth

17. Monocular Clues to Depth
 Relative size
 Interposition
 Linear perspective
 Aerial perspective
 Light and shade
 Motion parallax

23. Visual Direction
 Local sign – positional information
transferred from the retina to the motor
system – the fovea has a retinomotor value
of zero
 Retinal correspondence = single vision
 Retinal disparity = diplopia

24. Oculocentric Visual Direction

25. Egocentric Visual Direction

26. Cyclopean Eye

27. The Perception of Space
 Retinal corresponding points
 Horopter
 Retinal disparity
 Panum’s fusional area
 Physiological diplopia

28. The Horopter
 Vieth-Muller Circle
 Empirical Horopter

29. The Horopter

31.  Normal binocular single vision – the images
of the fixated object are bifoveal with no
manifest deviation of the eyes
 Anomalous binocular single vision – the
images of the fixated object are projected
from the fovea of one eye and an
extrafoveal position in the other eye – there
is a small manifest deviation of the eyes

32.  Misalignment of the two eyes can lead to
diplopia and confusion
 Diplopia – occurs when one object is seen in
two places
 Confusion – occurs when two dissimilar
objects are seen in the same place

33. Suppression and Retinal Rivalry
 Suppression
 Normal – physiological diplopia – also
known as suspension
 Anomalous – pathological diplopia and
confusion – cortical inhibition of suppressed
eye
 Retinal or binocular rivalry – rapid
alternation of dissimilar images

34. Testing Retinal Correspondence
 Bagolini lenses
 Red filter test
 Worth four dot test
 Hering-Bielschowsky afterimage test
 Foveo-foveal test of Cuppers

37. Worth Four Dot Test

38. Testing Suppression
 Worth four dot test
 Polaroid vis-à-vis test
 Amsler grid
 4 prism diopter base out test
 Red filter test
 Bagolini lenses

39. Polaroid Tests

40. Amsler Grid

41.  Versions – conjunctive eye movements –
the two eyes move in the same direction
 Pursuits
 Saccades

42.  Vergences – disconjunctive eye movements
– the eyes move in opposite directions
 Convergence
 Divergence
 Vertical vergence

43. Vergence
 Tonic
 Proximal
 Fusional
 Accommodative

44. Accommodation
 Tonic – in the absence of a visual stimulus, the
accommodation adopts an intermediate position of
0.5-1.0 D
 Proximal – resulting from apparent nearness of an
object
 Convergence – accommodation linked to
convergence
 Reflex – involuntary response to blur to maintain a
clear image
 Voluntary – not dependent on a stimulus