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Normal Optic Disc

Normal optic Disc

The optic disc is shaped like a doughnut with a pink neuroretinal rim and a central white depression called the physiologic cup.

Check out the color of the neuroretinal rim, which carries the axons of the retinal ganglion cells. It should be orange-pink. If its axons die, the rim will turn white. Inflammation, infarction, and compression are common causes.

Inspect the external margins of the neuroretinal rim. Are they distinct? Some fuzziness of the nasal margin is acceptable. Otherwise, the optic nerve may be pathologically swollen, particularly if the rim rises well above the retinal surface. Common causes of disc edema are increased intracranial pressure and optic nerve inflammation and infarction.

Inspect the physiologic cup. Its horizontal diameter should not exceed 1/2 the horizontal diameter of the entire disc (the "cup-to-disc ratio"). Otherwise, suspect pathologic optic disc cupping. Glaucoma is the commonest cause.

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