Optic nerve blood flow and its regulation.

Intracranial optic nerve blood flow was measured by the radiolabeled microsphere technique in 30 adult sheep under light barbiturate anesthesia. Regional blood-flow rates were determined under basal conditions. The responses of regional blood flow to alterations in PaCO2 and to changes in arterial blood pressure were also measured. Under basal conditions blood flow was comparable to that found in other cerebral white matter (14 +/- 1 ml/100 gm/min). Responses to hypercarbia and hypocarbia were also similar to reported measurements for other cerebral white matter. With alteration of arterial blood pressure, intracranial optic nerve blood flow remained constant within the limits of cerebral autoregulation.