Obstruction of aqueous humor outflow by cross-linked polyacrylamide microgels in bovine, monkey, and human eyes.

Abstract

Orcolon, a synthetic viscoelastic, may have contributed to refractory intraocular pressure (IOP) elevation after intracameral injection in some patients. Cross-linked polyacrylamide (microgels), an altered form of the polymer, was investigated as an etiologic candidate. Four adult rhesus monkeys underwent anterior chamber exchange with mock aqueous humor containing microgels in one eye and a vehicle in the other. Outflow facility (perfusion) and IOP (applanation) were determined before and at various times thereafter. Facility also was determined before and after microgel or vehicle infusion into organ-cultured individual human (n = 9) and paired calf (n = 6) anterior segments. Representative monkey and human eyes were examined by light and electron microscopy. In the microgel-infused monkey eyes, IOP was consistently higher, by approximately 5 mmHg for approximately 1 month. In all three species, microgel infusion acutely decreased facility by approximately 50% to 80%. In the living monkeys where longer-term observation and retesting were possible, a facility reduction of approximately 40% to 50% persisted for at least 1 to 2 months, and rechallenge again produced an acute 80% facility decrease and subsequent 10-mmHg IOP rise. Results of electron microscopic examination in human and monkey eyes showed accumulation of microgels in the cribriform meshwork and beneath the inner wall of Schlemm's canal, with no cellular alterations or inflammatory infiltrate. Cross-linked polyacrylamide microgels can produce an acute and longstanding obstruction of trabecular drainage experimentally, and might therefore do so clinically.