Treatment of glaucoma by use of transscleral neodymium:yttrium aluminum garnet laser cyclocoagulation in dogs

Abstract

Summary Neodymium:yttrium aluminum garnet (Nd:yag) laser energy was transsclerally applied to the ciliary body of 56 eyes of 37 dogs for treatment of glaucoma. Forty-four eyes were glaucomatous at the time of treatment, and 12 normotensive eyes with ciliary cleft closure were treated prophylactically. Glaucoma was primary in 35 dogs and secondary in 2 dogs (1 eye in each dog). Energy was delivered by a general surgical Nd:yag laser via a hand-held, 600-µc-diameter flexible quartz fiber. The mean (±sd) number of spots treated per eye was 35 (±9.7), with mean energy per burst of 7.1 (±2.6) J; mean total energy delivered to the eyes was 228 (±81) J. Follow-up evaluation was available for 42 eyes from 2 to 4 weeks after treatment, and for 32 eyes from 12 to 24 weeks after treatment. Treatment success, defined as maintenance of intraocular pressure <25 mm of Hg, was achieved in 83% (20/24) of glaucomatous eyes evaluated between 12 and 24 weeks of treatment. Of 4 treatment failures, 3 were eyes devoid of uveal pigment. The consistent acute effects of treatment were conjunctival vascular congestion and blood-aqueous barrier disruption, recognized clinically by the presence of aqueous flare. Hyphema developed in 16% (9/56) of eyes; hyphema resolved without complication in all but 2 eyes. A common long-term complication of treatment was cataract formation, recognized in 37% (12/32) of eyes evaluated at 12 to 24 weeks. Cataracts were sufficiently dense to obstruct vision in 4 eyes. Phthisis bulbi was observed in 1 eye. Results of this study indicate that Nd:yag laser cyclocoagulation is an effective means of controlling intraocular pressure in dogs with glaucoma. Cataract formation is a potential complication of treatment.