Pupillary pathway & Field Defects

Dr. K. Srikanth MS;D.O;DNB;

Monocular blindness• Lesion of the left optic nerve results in complete blindness of the left eye.

• Causes :• optic atrophy, • optic neuritis,

• traumatic avulsion of optic nerve.

Bitemporal hemianopsia• Lesions affecting the optic chiasm – pituitary adenoma, craniopharyngioma meningioma

Homonymous Hemianopia• lesions of the optic tract, the lateral geniculate nucleus, the optic radiations, and the cerebral visual (occipital) cortex.

• In adults the common causes are brain

tumors, trauma, surgical interventions.

• In children the common causes are neoplasm, cerebrovascular disease, trauma.

Superior/Inferior quadrantanopia• Lesion of optic radiation.

• Lesion of the meyer’s loop ( temporal pathway) – Superior quadrantanopia (pie in the sky).

• Lesions of the parietal pathway – inferior quadrantanopia (pie on the floor)

• Causes – neoplasm, inflammatory process, ischemia, infection (eg: encephalitis)

Traquair’s hill of vision• Traquair defined visual field as island of vision in a sea of darkness.

• Hill of vision is a 3D representation of the retinal light sensitivity.

• Sea represents the area of darkness.

• The outer aspect extends 50o superiorly, 60o nasally, 70oinferiorly, 90o temporally.

Perimetry• Perimetry is the measurement of visual functions of the eye

at topographically defined loci in the visual field.

• Usually each eye is tested separately, however when both eyes are tested together it is binocular field of vision.

• Types of perimetry – kinetic, static, suprathreshold, threshold

Kinetic perimetry• It is a 2D assessment of boundary of hill of vision

• Moving stimulus of known intensity ( luminance ) is presented from non seeing area to a seeing area until it is perceived.

• Stimulus is moved at a steady speed

• Point of perception is recorded on a chart

• Goldmann perimeter most commonly used.

Static perimetry• Location of stimulus remains fixed.

• The intensity of stimulus is increased until it is seen by the subject or decreased until it is no longer seen.

• Most commonly used automated perimeter is the Humphrey Field Analyzer (HFA)

• Others – Henson, Dicon & Octopus

Important questions• Draw dig. of pupillary light reflex?• Enumerate any 4 field defects of the visual pathway?• What are the causes of monocular blindness?• What are the causes of homonymous hemianopia?• What are the causes of bitemporal hemianopsia?• What are the causes of quadrantanopia?• What are the field defects seen in case of a lesion in the visual

cortex and their causes?