Instability of eye position in the dark in cerebellar degeneration

Fourteen cases of spinocerebellar degeneration were examined. While the patients attempted to keep their eyes in the primary position, horizontal eye movements were recorded for 1 min in total darkness by infrared reflection oculography. Instability of eye position in the dark was observed in 10 patients. The range of the eye position error was 3-6 degrees in 6 patients, 6-10 degrees in 3 patients and over 10 degrees in 1 patient. These results indicate that the cerebellum plays an important role in extraretinal (nonvisual) eye position control.