Abstract

A 23-year-old male western lowland gorilla (Gorilla gorilla gorilla) presented with a one-week history of progressive vision impairment. Additional clinical signs at presentation included intermittent profound lethargy and presumed head pain. Initial exam under anesthesia (day 0) revealed bilateral glaucoma (IOP 50–54 mm Hg o.d. and 55–60 mm Hg o.s.). Treatment initially consisted of oral acetazolamide (500 mg PO daily, increased to BID; Heritage Pharm, Eatontown, NJ, USA) and ibuprofen (800 mg PO daily; Major Pharm, Livonia, MI, USA). The animal underwent ciliary body ablation laser surgery on day 14 using a transscleral micropulse cyclophotocoagulation (240 sec/eye, 120 sec ventral, 120 sec dorsal, o.u. at 2000 mW x 31.3% duty cycle) (novel MicroPulse P3 Glaucoma Device, Iridex, Mountain View, CA, USA). Post treatment, the animal’s vision was initially worse, which was attributed to postoperative uveitis, and on day 22 the gorilla developed bilateral hyphema. Neither complication is common in humans treated in the same manner, but both improved with treatment including topical dorzolamide/timolol o.u., TID (Hi-Tech Pharm., Amityville, NY, USA) and neomycin/polymyxin/dexamethasone drops o.u., BID (Bausch & Lomb, Tampa, FL, USA). Vision returned to pre-procedure levels by day 49. Recheck of IOP under anesthesia on day 53 revealed resolution of the glaucoma (IOP 13 mm Hg o.s., 9 mm Hg). On day 58, the animal started displaying intermittent episodes of disorientation. Treatment with memantine (5 mg PO daily initially, increased to BID after 5 days; Actavis Pharm., Parsippany, NJ, USA) was initiated, and the disorientation improved over the subsequent two months. It is unclear if this disorientation was related to the unknown underlying cause of the glaucoma or possibly simply a result of decreased vision subsequent to the glaucoma. Over the following four months, oral and topical medications were weaned with the exception of memantine, which is ongoing. Although significant vision loss resulted from the glaucoma, the vision is stable, no signs of pain are present, and the animal is able to function as the dominant male in the social group.

Acknowledgments

The authors thank the Iridex company for donating time and use of their laser. The authors also thank the veterinary and mammal department staff of the Wildlife Conservation Society for the ongoing care of this animal.