Time dependent effects of sympathetic denervation on aqueous humor dynamics and choroidal blood flow in rabbits

Purpose. This study investigates the time-dependent effects of superior cervical ganglionectomy (SCGx) on aqueous humor dynamics and ocular blood flow in rabbits. Methods. Measurements were made at various times between 24 hours and 12 months after SCGx. Intraocular pressure (IOP) was measured by pneumatonometry, aqueous flow by fluorophotometry and outflow facility by tonography. Uveoscleral outflow was determined by an intracameral tracer infusion technique and blood flow to the choroid was evaluated with fluorescent microspheres. Values in denervated eyes were compared with the contralateral, normally-innervated eyes using a paired Student's two-tailed t-test. Results. At 24 hours after SCGx, IOP in denervated eyes was less than in normally-innervated eyes (14.6 ± 0.8 vs 20.1 ± 1.5 mmHg, 27%, p < 0.002). At one month, IOPs were not different between eyes. Compared with normally-innervated eyes at 10-12 months, IOP in denervated eyes was greater (20.4 ± 0.7 vs 17.2 ± 0.9 mmHg, 19%, p < 0.001), outflow facility was less (0.15 ± 0.02 vs 0.21 ± 0.01 μl/min/mmHg, 29%, p < 0.01) and blood flow to the choroid was less (12.1 ± 5.0 vs 16.2 ± 6.0 ml/min/gm tissue, 25%, p < 0.05). Aqueous humor flow was not significantly altered by SCGx at any time. Conclusions. The reduction in IOP at 24 hours after SCGx was not due to any change in aqueous flow or uveoscleral outflow (current study) but rather to an increase in outflow facility (previous studies). At 10-12 months, IOP was elevated because outflow facility was significantly reduced. The reduction in choroidal blood flow at 10-12 months may have occurred because of the increased IOP.