Evaluation of Valved and Nonvalved Gonioimplants in 83 eyes of 65 dogs with Glaucoma

Abstract

A consecutive series of 83 acutely glaucomatous eyes from 65 dogs receiving gonioimplant surgery from 1992-1995 was reviewed. Eighteen dogs were implanted bilaterally and forty-seven unilaterally, with seven eyes receiving two gonioimplants. The gonioimplants utilized were either a T-shaped, silicone nonvalved implant, the Ahmed valve with large anterior chamber tubing (VS-2), or the Ahmed valve with a silicone strap added (VS-2 Si). The criteria for success were retention of vision, and/or maintaining intraocular pressure (IOP)<20 mm Hg, with or without topical or systemic antiglaucoma medications. The median time for elevated IOP to occur postoperatively was 4, 15, and 10 months respectively (41 eyes), for the nonvalved, VS-2, and VS-2-Si implant groups. The median time for vision loss to occur postoperatively was 4, 6, and nine months, respectively (32 eyes), for the nonvalved, VS-2, and VS-2-Si implant groups. Fifteen of the 22 eyes that had an IOP<20 mm Hg were visual one year postoperatively. The valved VS-2 and VS-2-Si gonioimplants were the most successful at preserving vision and maintaining an IOP<20 mm Hg. The complications encountered in the overall study are discussed and future alternatives proposed.