ENERGY-LEVELS NEEDED FOR CYCLOPHOTOCOAGULATION - A COMPARISON OF TRANSSCLERAL CONTACT CW-YAG AND KRYPTON LASERS IN THE RABBIT EYE

The energy levels needed for cyclophotocoagulation using either transs cleral contact krypton or cw-YAG lasers were compared in pigmented rab bits. The same transscleral laser probe was used for both lasers. With the krypton laser, 0.25 J of energy caused macroscopically detectable lesions, and 1.5 J led to widespread destruction of the ciliary body. With the cw-YAG laser, the first detectable lesions were produced at 0.5 J. Similarly, at higher energies, twice as much energy was require d using the cw-YAG as compared with using the krypton laser to produce comparable lesions. Histologically, lesions of the same macroscopic s everity made with the two lasers were similar. We conclude that the tr ansscleral contact krypton laser is an efficient instrument for cyclop hotocoagulation. Although these results may not be directly applied to human eyes, it appears that the poorer scleral transmission of the kr ypton beam is offset by its higher level of absorption in the pigmente d epithelium of the ciliary body.