Optic Nerve and Visual Pathway

Optic Disc Abnormalities

Afferent Visual pathway

Structures responsible for perceiving relaying and processing visual informaiton

Retina, optic nerves, chiasm, tracts, lateral geniculate nuclei, optic radiations, occipital striate cortex

Macula: Fovea is the center of the macula

The optic disc: 1.2 million axons coalesce to form the optic nerve

Optic Nerve

Function

COnduct electrical signal from eye to brain to form basis for vision

Assess Function

Visual acuity, color vision, Pupillary responses, confrontation visual fields

Optic Neuropathy

Abnormal optic nerve function

Normal Optic Disc

Color: Orange/pink

Margins: Distinct

Cup to disc ratio: 0.3

Optic Disc Abnormalities

Congenital

Optic nerve hypoplasia, myelinated nerve fibre layer, tilted disc syndrome, optic nerve coloboma

Acquired

Normal (inflammatory, ischemic)

Swollen (blurred margin, decreased cup to disc ratio), True Edema (Papilledima, Primary optic neuropathy), Pseudo-edema (Drusen<

Pale/Atrophy Optic Disc: Ishcemic optic neuropathy/Chronic progressive optic neuropathy

Cupping: Cup appears pale, and rim has mild pallor, large cup to disc ratio

Glaucoma/Compressive Optic Neuropathy presents with cupped optic disc

Deficiencies

One Eye: Optic Nerve

Bitemporal: Optic Chiasm

Homonymous: Posterior to the chiasm

Superior Defects: Relatively inferior

Inferior defects: Relatively superior

Retrochiasmal lesions: Lesion opposite side to the field defect