Histological and physiological studies of cyclocryotherapy in primate and human eyes

In human and primate eyes treated with cyclocryotherapy, the epithelial and capillary elements of the ciliary processes were destroyed and replaced by fibroblast-like cells. The trabecular meshwork and Schlemm's canal were histologically affected by cyclocryotherapy. Damage to the angle structures impaired aqueous outflow. This damage may partially counteract the favorable effect of cryotherapy on intraocular pressure. The loss of ciliary epithelium resulted in breakdown of the blood-aqueous barrier and accounted for chronic aqueous flare. Correlation of external cryoprobe temperatures and internal ciliary pars plicata temperatures in live and enucleated monkey eyes demonstrated the uveal blood flow attenuates the effect of cryotherapy on the ciliary body.