Dorzolamide Increases Retinal Oxygen Tension After Branch Retinal Vein Occlusion

Abstract

Purpose:: Dorzolamide increases retinal oxygen tension and optic nerve oxygen tension in pigs. Experimental Branch Retinal Vein Occlusion (BRVO) decreases retinal oxygen tension in cats and minipigs. We wanted to study the effect of dorzolamide after experimental induction of BRVO in pigs to see whether dorzolamide increases oxygen tension in retinal areas affected by BRVO.

Methods:: Experimental BRVO was induced with a diathermy needle on a branch retinal vein close to the optic disc. Preretinal oxygen tension was measured 0.5 mm above the retina with a polarographic electrode. In one group of five pigs, preretinal oxygen tension was measured before BRVO, one and three hours after BRVO, and finally after 500 mg dorzolamide intravenously. Oxygen measurements were made above the BRVO-affected area and compared to measurements from two retinal areas not affected by BRVO. In a second group BRVO was induced in five pigs and one week later, retinal oxygen tension was measured above similar retinal areas as in the first group, both before and after intravenous administration of 500 mg dorzolamide.

Results:: Retinal oxygen tension was significantly decreased in the BRVO-affected areas both one hour (-0.55 kPa ± 0.29 (-21% ± 11)) and three hours (-0.91 kPa ± 0.15 (-36% ± 6)) after BRVO-induction, while oxygen tension was significantly increased in nonBRVO areas one hour after BRVO (+0.51 kPa ± 0.14 (+19% ± 6)), but not three hours after BRVO. One week after BRVO-induction, retinal oxygen tension was 30% ±14 (0.67kPa ± 0.31) lower in BRVO-affected areas compared to nonBRVO areas. Dorzolamide increased oxygen tension significantly in BRVO-affected areas both three hours (+0.47 kPa ± 0.11 (+28% ± 6)) and one week (+1.09 kPa (+46% ± 12) after BRVO-induction.

Conclusions:: Hypoxia induced by experimental BRVO remains significant the first week after BRVO. Dorzolamide increases retinal oxygen tension in hypoxic BRVO-affected areas both three hours and one week after experimental BRVO-induction in pigs. Dorzolamide may offer therapeutic opportunities after branch retinal vein occlusion and other ischemic diseases of the retina and optic nerve, like diabetic retinopathy and glaucoma.

Keywords: drug toxicity/drug effects • vascular occlusion/vascular occlusive disease • hypoxia