Optic Nerve Pit

During a routine ophthalmologic examination, a round depression in the temporal region of the optic disc was found in a 35-year-old woman. Her past ocular history was noncontributory.

This is an optic nerve pit, a congenital anomaly that is thought to have a coloboma-like origin and is attributed to incomplete closure of the fetal fissure. This defect is sometimes called an “atypical coloboma.”

The optic pit pictured here is typical; it is temporally located, singular, and unilateral. These defects may appear olive gray, yellow, or white and vary in shape from round to oval. Circumpapillary chorioretinal atrophy and pigmentation also can occur, as seen here.

Dr Leonid Skorin, Jr, of Dixon, Ill, cautions that fluid buildup can cause a nonrhegmatogenous retinal detachment in the macular area in as many as 75% of patients with an optic pit. The origin of this fluid is not known, but it may arise from the vitreous humor, cerebrospinal fluid, choroidal vessels, or disc capillaries. The fluid can resorb spontaneously only to reappear later.

Dr Skorin stresses that patients with an optic pit need to have routine ophthalmologic examinations. Encourage them to monitor their own vision at home using an Amsler's chart.

Metamorphopsia, or distortion of the black-and-white, geometric grid pattern of this chart, will indicate early signs of fluid buildup.