Effect of Raised Intraocular Pressure on the Retinal and Choroidal Circulation

Abstract

The effect of acutely elevated intraocular pressure upon the retinal and choroidal circulationteas studied in young farm pigs. Still and cine fluorescence angiograms were used to document the circulatory status. Increased ocular pressure slowed filling in both retinal and choroidal vessels. The choriocapillaris fills as small patches which eventually coalesce, the initial filled areas resembling patchy choroiditis or the pattern of drusen. Increased intraocular pressure slows the forward velocity of fluorescein in retinal vessels, but the no-flow point depends on the combination of intraocular and systemic arterial pressure. There was no evidence of selective perfusion of "preferential channels" even at high intraocular pressure. The radial peripapillary capillaries were seen to derive primarily from intraretinal arterioles. Embarrassment of flow in the radial capillaries at high intraocular pressure was seen in some studies, but this was not a constant feature. It was also noted that the blood supply of the optic disc in the pig appears distinct from that of the surrounding retina, and in several experiments the disc was noted to fluoresce before any retinal vessels filled.