Aqueous humor dynamics in monkeys with laser-induced glaucoma

This study determines the effects of laser-induced glaucoma on aqueous humor dynamics of 18 cynomolgus monkeys. Baseline measurements of 12 monkeys included intraocular pressure (IOP) by pneumatonometry, aqueous flow by fluorophotometry and outflow facility by tonography. Beginning 4 to 14 days later, the trabecular meshwork of one eye was treated repeatedly with laser photocoagulation until elevated IOP was induced. Thirty-six to 75 days after the last laser treatment, all measurements were repeated. Between 1.7 and 11.4 years after laser treatment, the same 12 monkeys plus 6 additional monkeys underwent IOP and aqueous flow measurements. In addition, outflow facility was determined with fluorophotometry, and uveoscleral outflow was both calculated (n=18) and measured with an intracameral tracer (n=7). In glaucoma eyes compared to control eyes (n=12), IOP was increased (p<0.04) by at least 8 mmHg at Time 1 (1 to 3 months) or Time 2 (3 to 4 years) after laser treatment; aqueous flow was reduced (p=0.0007) by 46% at Time 1 but returned to baseline levels at Time 2; tonographic outflow facility was reduced (p=0.0008) by 71% at Time 1. In lasered eyes compared to control eyes, fluorophotometric outflow facility was reduced (p=0.0008; n=18) by 63%, and uveoscleral outflow was increased (p<0.05), whether calculated or measured with tracers at least 1 year after laser treatment. The increased IOP in monkeys with laser-induced glaucoma was caused by a sustained reduction in outflow facility. The uveoscleral outflow increase was not enough to prevent the rise in IOP.