Effect of changes in intraocular pressure on the retinal microcirculation

Abstract

The relationship between retinal blood flow and intraocular pressure was studied in 9 healthy young pigs. Despite a progressive decrease in the blood flow velocity as the intraocular pressure was raised, the volume flow through the retinal circulation was maintained at near normal levels until the perfusion pressure was reduced by an average of 63%. This preservation of volume flow was produced by dilatation of the retinal arteries. Further increases in the intraocular pressure led to a rapid decrease in flow and the theoretical noflow point in the retinal arteries was calculated to be 8 mm.Hg. After sudden reduction of intraocular pressure after a period of elevation, volume flow was increased by an average of 86% through reactive hyperemia. Reduction of normal intraocular pressure by paracentesis did not increase blood flow by more than 20%. These comparisons suggest that compression/decompression of the globe is likely to be substantially more effective in improving volume flow than aqueous puncture. Reversible cupping of the optic disc was observed at high intraocular pressures.