Gray crescent in the optic nerve head.

Twenty-nine patients had a slate-gray crescent within the peripheral tissue of the optic nerve head. Twenty-five of the patients were black; an examination of 100 consecutive black patients revealed the gray crescent in 12 cases. The gray crescents were usually bilateral and were most often located along the temporal or inferotemporal disk margin. Failure to recognize the anatomic location of the gray crescent may lead to misdiagnosis of disk cupping.