DIODE-LASER-PUMPED, FREQUENCY-DOUBLED NEODYMIUM-YAG LASER PERIPHERAL IRIDOTOMY

BACKGROUND AND OBJECTIVE: The solid-state, continuous-wave, frequency- doubled neodymium:yttrium-aluminum-garnet (Nd:YAG) laser pumped by a d iode laser has several advantages, including air cooling, higher elect rical to optical efficiency ratios, portability, and the use of standa rd 110-V AC electrical service. The authors wanted to evaluate the use of the frequency-doubled Nd:YAG laser for peripheral iridotomy and to compare the tissue interactions of this laser with those of the argon laser. MATERIALS AND METHODS: The authors developed a diode laser-pum ped, solid-state, and portable frequency-doubled Nd:YAG laser with a w avelength of 532 nm. The effects of peripheral iridotomy with the freq uency-doubled Nd:YAG laser and the argon laser were evaluated in pig e yes in vitro and in rabbit eyes in vivo. Specimens were prepared for l ight microscopy and scanning electron microscopy. RESULTS: The frequen cy-doubled Nd:YAG laser successfully created patent iridotomies in all animal eyes treated. The following parameters were used to create pen etrating burns: duration of 0.1 second, spot size of 100 mu m, and pow er of 500 mW. In rabbit eyes, the mean number of pulses (P =.16) and t he total energy required (P =.21) for iridotomy were not significantly different for the argon laser compared with the frequency-doubled Nd: YAG laser. Gross and histologic evaluation showed similar thermal effe cts in iris tissues for both the frequency-doubled Nd:YAG laser and th e argon laser. The mean zone of thermal damage was 178 +/- 19 mu m for the frequency-doubled Nd:YAG laser and 163 +/- 24 mu m for the argon laser (P =.14). Scanning electron microscopy showed less disruption of the surface of the lesion for the frequency-doubled Nd:YAG laser comp ared with the argon laser. CONCLUSIONS: Successful peripheral iridotom y can be performed with the frequency-doubled Nd:YAG laser. Coagulativ e effects with the frequency-doubled Nd:YAG were similar to those with the argon laser, and the thermal damage zones were comparable in size .