OBSTRUCTION OF AQUEOUS-HUMOR OUTFLOW BY CROSS-LINKED POLYACRYLAMIDE MICROGELS IN BOVINE, MONKEY, AND HUMAN EYES

Purpose: Orcolon, a synthetic viscoelastic, may have contributed to re fractory intraocular pressure (IOP) elevation after intracameral injec tion in some patients. Crosslinked polyacrylamide (microgels), an alte red form of the polymer, was investigated as an etiologic candidate. M ethods: 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 d etermined before and after microgel or vehicle infusion into organ-cul tured individual human (n = 9) and paired calf (n = 6) anterior segmen ts. Representative monkey and human eyes were examined by light and el ectron microscopy. Results: In the microgel-infused monkey eyes, IOP w as consistently higher, by approximately 5 mmHg for approximately I mo nth. In all three species, microgel infusion acutely decreased facilit y by approximately 50% to 80%. In the living monkeys where longer-term observation and retesting were possible, a facility reduction of appr oximately 40% to 50% persisted for at least 1 to 2 months, and rechall enge again produced an acute 80% facility decrease and subsequent 10-m mHg IOP rise. Results of electron microscopic examination in human and monkey eyes showed accumulation of microgels in the cribriform meshwo rk and beneath the inner wall of Schlemm's canal, with no cellular alt erations or inflammatory infiltrate. Conclusions: Cross-linked polyacr ylamide microgels can produce an acute and longstanding obstruction of trabecular drainage experimentally, and might therefore do so clinica lly.