Cyclodestructive operations differ according to (a) the destructive energy source and (b) the route by which the energy reaches the ciliary processes. In the 1930s and 1940s, several energy sources were evaluated, including diathermy, β-irradiation, and electrolysis, although only cyclodiathermy achieved clinical acceptance. Cryotherapy was introduced in the 1950s and became the most commonly used cyclodestructive procedure. However, subsequent experience with laser cyclophotocoagulation showed clear advantages over other techniques, and it has become the preferred cyclodestructive operation. Other cyclodestructive techniques include therapeutic ultrasound and microwave cyclodestruction. Each of these energy sources may be delivered by the transscleral route, in which the destructive element passes through conjunctiva, sclera, and ciliary muscle before reaching the ciliary processes. Transscleral cyclodestructive operations have the advantages of being nonincisional and relatively quick and easy. However, significant disadvantages include the inability to visualize the processes being treated and damage to adjacent tissue, leading to unpredictable results and frequent complications. With the advent of laser energy as the cyclodestructive element, alternative delivery routes are possible, including transpupillary and intraocular.
