Recovery of spatial vision following shunting for hydrocephalus

M. E. Tytla and J. R. Buncic
Department of Ophthalmology, Hospital for Sick Children, Toronto, Ontario, Canada.

Individuals with papilledema due to intracranial hypertension often exhibit a loss of contrast sensitivity confined to low spatial frequency (coarse detail), which can disappear following treatment of the intracranial hypertension. The basis of the initial loss may be revealed by the rate of sensitivity recovery. We monitored the contrast sensitivity of seven patients immediately before and after surgical treatment in which a shunt was placed for intracranial hypertension. Compared with normal controls, the 13 of 14 eyes with papilledema exhibited the characteristic preshunt loss of sensitivity. For the first 3 days after shunt placement, sensitivity remained approximately equal to preshunt levels. By postshunt days 4 through 6, sensitivity rapidly normalized and remained normal for up to 1 year. Based on the rate and pattern of sensitivity normalization, we conclude that the initial loss represents an interaction of axoplasmic stasis with ischemia at the level of the optic nerve.