OPTIC NEUROPATHY FOLLOWING SIMULATION OF ORBITAL HEMORRHAGE IN THE NONHUMAN PRIMATE

The goal of the study was to determine, using a nonhuman primate (NHP) model, the minimum duration of elevated intraocular pressure (IOP) (i nduced by an inflated catheter) necessary to produce significant visua l system deficits. in Old World monkeys (Macaca mulatta), a catheter n as placed retrobulbarly in one orbit and inflated with saline ibr eith er 180 min (10 monkeys) or 240 min (six monkeys subjects). Baseline co lor fundus photographs, monochromatic photography, fluorescein angiogr aphy, and IOP measurements were performed preoperatively and at either 2, 4, or 6 weeks postoperatively on both eyes of each monkey prior to killing and histological analysis. Optic neuropathy was demonstrated in eight of these NHPs. In the two most severe cases (240 min inflatio n condition), complete nerve fiber atrophy with central retinal artery occlusion was observed. Sector nerve fiber atrophy, extending from th e temporal disc to beyond the macula, was noted in the other six monke ys, five of which were in the 180 min inflation condition. Thus, optic neuropathy, sufficient to produce visual loss, was noted following in creased IOP (greater than or equal to 50 mm Hg) for 180 min or 240 min . These data emphasize the need for timely intervention to mitigate th e potential detrimental effects of retrobulbar hemorrhage when it occu rs in humans.