To the Editor.–The excellent report of Smith et al in the Archives (95:284-288, 1977) is one of three recent experimental studies of cyclocryotherapy in primates.1,2 There are some possible conclusions to be drawn from the comparison of these three reports that may be of significant importance to the clinical application of cyclocryotherapy.
One of the major variables in cyclocryotherapy is the duration of freezing. In their rhesus monkeys, Smith et al treated one half of the eye at −70 C for 30 seconds, with an identical refreeze. The early effects were loss of some nonpigmented ciliary epithelium and disorganization of pigmented ciliary epithelium. Two months or longer after this treatment, the ciliary processes were predominantly normal. The intraocular pressures were not measured. In owl monkeys,2 one half of the eye was treated once at −65 C for 60 seconds. The early destruction of both ciliary epithelial layers was
Quigley HA. Clinical Application of Cyclocryotherapy. Arch Ophthalmol. 1977;95(4):714. doi:10.1001/archopht.1977.04450040180031