Periodic alternating nystagmus clearing after vitrectomy.

Periodic alternating nystagmus 1) may be related to vestibulocerebellar system disease, 2) may occur with loss of vision, and 3) may be congenital in origin. We report the case of a patient with acquired periodic alternating nystagmus in whom the nystagmus followed bilateral vitreous hemorrhages. Upbeating nystagmus was interposed between the right beating and left beating phases. Bilateral vitrectomy resulted in the prompt disappearance of the nystagmus. The importance of visual function in relation to periodic alternating nystagmus and associated motility disturbances is emphasized.