Neodymium:yttrium, aluminum, and garnet laser energy delivered transsclerally to the ciliary body of dogs.

Using a hand-held optical fiber, a surgical neodymium:yttrium, aluminum, and garnet laser was used transsclerally on the left ciliary body of 25 dogs. Dogs were assigned to groups and were given low (100 J) and high (238 J) energy levels. In 12 dogs given 100-J energy, the intraocular pressure decreased a mean value of 6 mm of Hg below that in the untreated right eye. However, intraocular pressure returned to the pretreatment value 1 week after treatment. Intraocular lesions were not found by histologic examination 28 days later. In the second group of 13 dogs treated with 238-J energy, 6 were euthanatized 7 days after treatment and 7 were euthanatized 28 days after treatment. A mean decrease in intraocular pressure of 10 mm of Hg in the treated left eye, relative to the untreated right eye, persisted throughout the evaluation period. In eyes examined histologically 7 days after treatment, ciliary hemorrhage and necrosis were prominent. Other histologic changes were minimal and consisted principally of iris stromal hemorrhage. Of 7 dogs examined for 28 days after treatment, 6 remained sighted; in 1 dog, extensive intraocular hemorrhage occurred, eventually resulting in phthisis bulbi. Ciliary atrophy and fibrosis were the important histologic lesions observed 28 days after treatment. Laser energy delivered transsclerally by this optical system effectively induced ciliary necrosis and may be an effective treatment for canine glaucoma.