Ciliary body temperatures during cyclocryotherapy in the clinically normal dog

Three cryosurgical units were compared on the basis of the ability of each unit to freeze the ciliary body of enucleated normal canine eyes. The coldest average temperatures reached were -13.4 C, -4.3 C, and -17.6 C. One of the units was then used to freeze the ciliary body in the left eye of 25 dogs for 5 minutes. Ciliary body temperatures were monitored every 15 s during cyclocryosurgery. In 18 eyes in situ, the coldest average temperature reached was -13.4 C. In 7 proptosed globes, the coldest average temperature reached was -13.8 C. The results were not significantly different (P less than 0.05). The effects of the cryosurgery and centesis procedure were monitored daily by direct observation and Schiotz's tonometry. Histologic changes from the procedure were evaluated at 5 minutes, 1 week, 1 month, and 6 months after surgery. Intraocular pressure returned to the normal range within 1 to 2 weeks, the anterior uveitis subsided in 7 to 10 days, and ciliary body epithelium was histologically normal within 6 months after surgery.