Optic nerve circulation and ocular pressure: contribution of central retinal artery and short posterior ciliary arteries and the effect on oxygen tension.

Blood-flow rate in the optic nerve of the rhesus monkey 4 mm. behind the globe monitored by the heated thermocouple and tissue p02 measurement is found to be influenced by ocular pressure level. Ligation of central retinal artery reduced flow rate to 79 per cent of normal but did not influence the effect of IOP on blood-flow rate. Ligation of short posterior ciliary arteries reduced blood-flow rate to 21 per cent of normal and virtually eliminated the IOP effect. Raising IOP to above systolic arterial pressure level reduced blood-flow rate to 17 per cent of normal. At IOP levels greater than 50 mm. Hg, the reduction in blood-flow rate and in Po becomes marked and may be sufficient to produce primary lesions at this site.