Intraocular Pressure and Outflow Facility are Unchanged Following Acute and Chronic Intracameral Chondroitinase ABC and Hyaluronidase in Monkeys

We determined the effect of chronic and acute loss of glycosaminoglycans from the aqueous outflow pathway on intraocular pressure (IOP) and outflow facility in the subhuman primate eye. For the study of the chronic effects of the GAGases, cynomolgus monkeys received intracameral injections of hyaluronidase (Streptomyces, 5 or 50 units, n¯2) or chondroitinase ABC (0±05 or 0±25 units, n¯2) biweekly for 8 months (4 months for each dose). IOP was measured at 3, 7, 10 and 14 days after each injection. Outflow facility (2-level constant pressure) was determined at 2, 4, 6, and 8 months. Monkeys were killed 6 days after the last injection. The changes in the distribution of hyaluronic acid and sulfated proteoglycans in the outflow pathway were examined using substrate-specific histochemical techniques. The acute effects of these enzymes on outflow facilities (30 min or 2 hr after enzyme) were determined in another group of animals (n¯4 for each time enzyme−"). IOP and outflow facility were unchanged compared to controls (heat inactivated enzyme) at any time in the chronically or acutely treated monkeys. Hyaluronic acid staining was absent in the outflow pathways of eyes treated chronically with hyaluronidase compared with control eyes, while collagen-associated sulfated proteoglycans were decreased but not completely removed by the chronic chondroitinase ABC treatment. Chronic loss of these glycosaminoglycans from the trabecular meshwor