Cyclodestructive surgery for glaucoma: past, present, and future.

When surgical attempts to control glaucoma by improving aqueous outflow are not successful, the alternative approach is usually to reduce aqueous inflow by a cyclodestructive procedure. Cyclodestructive elements that have been tried in the past include diathermy, electrolysis, and beta irradiation. Cyclocryotherapy is presently the most commonly used cyclodestructive procedure, although this operation has significant limitations, and newer techniques are being evaluated utilizing laser energy or ultrasonic radiation. Each of these procedures uses a transcleral approach, which has the disadvantages of (1) the inability to precisely quantitate the destruction of the ciliary processes, and (2) damage to adjacent tissue. Transpupillary cyclophotocoagulation minimizes these problems, but is limited to the small number of eyes in which adequate gonioscopic visualization of the ciliary processes can be achieved. An alternative approach for aphakic eyes is intraocular cyclophotocoagulation, utilizing an endophotocoagulator through a pars plana incision. Depending on the status of the eye, visualization for this technique can be accomplished either by the transpupillary route or with an endoscope.