Binocular Vision

Horopter

Empirical Horopter

Panum’s Area

Panum’s Area

Physiological Basis

Requirements for Stereopsis

❚ Binocular Overlap

❚ Partial Decussation

❚ Coordinated Eye Movements

Overlapping Fields: Panoramic

Overlapping Fields: Binocular

Overlapping Fields: Binocular

Partial Decussation

Coordinated Eye Movements

❚ Gaze Holding

❚ Gaze Shifting

Retinal Function

Visual Function

Summary

❚ Object on horopter will stimulate corresponding points

❚ Objects within Panum’s region create retinal disparity and signal depth

❚ Objects beyond Panum’s region produce diplopia

Reflexes

❚ Unconditioned or innate

❚ Conditioned

Oculomotor Reflexes

❚ Postural

❚ Psycho-optical

Postural reflexes

❚ Oldest reflexes found in vertebrates

❚ Stabilise eyes with respect to gravity

❚ Stabilise eyes with respect to head and body movement

Vestibular System

Vestibular System

❚ Static reflexMaintains orientation relative to gravity

❚ Kinetic reflexStabilise with respect to head movement

VOR

Gaze-Holding

Gaze-Holding: Visual Perception

Gaze-Holding

Gaze-Holding: Visual Perception

Gaze-Holding: Visual Perception

Gaze-Shifting

Psycho-Optical Reflexes

❚ Fixation reflexRefixation

Pursuit

Steady fixation

❚ Fusion reflex

Development of Visual Function

Fixation Eye Movements

Refixation Movements

Development of Saccades

Pursuits: Infant

Pursuit: Naïve Adult

Optokinetic Nystagmus (OKN)

OKN

OKN

❚ Can be used to estimate acuity❚ Used to evaluate binocular development❚ Normal OKN at 4 months❚ Slow phase velocity 25 degree/sec in

newborns❚ Slow phase velocity 40 degrees/sec in

adults

OKN with BV anomalies

❚ OKN is asymmetric❚ Slow phase has higher velocity to

nasalward motion than temporal motion❚ Response seen in affected eye and normal

eye❚ OKN remains asymmetrical in adults who

have had congenital cataract or strabismus in early life

Development of Accommodation

Development of Accommodation

Development of Vergence

Accommodation and Vergence

❚ AC/A

❚ CA/C

Summary

❚ Stereopsis requires binocular overlap, partial decussation and coordinated eye movements

❚ Eye movements have various components❚ Development of eye movements rapid❚ Vergence high order control