Effect of transpupillary argon laser cyclophotocoagulation on anterior chamber oxygen tension in rabbit eyes

We measured anterior chamber O2 tension and intraocular pressure (IOP) in normal, untreated controls and in rabbits treated with transpupillary argon laser cyclophotocoagulation. Normal anterior chamber O2 tension was 35 +/- 6 mmHg in room air and increased slowly when the rabbits breathed 100% O2. Between 3 days and 6 weeks after cyclophotocoagulation, O2 tension dropped 54%. Between 12 and 19 weeks after cyclophotocoagulation, changes in O2 tension were not statistically significant compared with the control. Normal IOP was 12 +/- 1 mmHg. Between 3 days and 6 weeks after cyclophotocoagulation, changes in the IOP were not statistically significant compared with the control. Light microscopy showed laser damage to the capillaries in the ciliary body as well as to the ciliary epithelium, particularly between 3 days and 6 weeks after treatment. We conclude that anterior chamber O2 tension under normal conditions reflects at least uveal vascular delivery of O2 and that cyclophotocoagulation, by destroying the ciliary epithelium-capillary complex, causes a decrease of oxygenation of the aqueous humor in the anterior chamber.