PICOSECOND NEODYMIUM-YTTRIUM LITHIUM-FLUORIDE (ND-YLF) LASER PERIPHERAL IRIDOTOMY

PURPOSE: We evaluated the picosecond neodymium:yttrium lithium fluorid e (Nd:YLF) laser for performing peripheral iridotomies of predetermine d size and shape in various types of irides. METHODS: In the first par t of the study, we determined operating parameters from performing 60 iridotomies in human cadaver eyes. Subsequently, using the parameters obtained in cadaver eyes, iridotomies were created in eyes of patients with primary angle-closure glaucoma. RESULTS: In the cadaver eyes, th e optimal parameters were a rectangular cutting pattern of 0.3 x 0.3 m m, 500-mu m cutting depth, 50-mu m spot separation, 200 to 400 mu J of energy per pulse, 200 to 400 pulses per second, and no focal offset d istance, In 18 eyes of 11 patients, iridotomies with well-defined marg ins and size were created. Minimal hemorrhage occurred intraoperativel y in ten of 18 eyes (55.6%), which did not affect the outcome of the p rocedure. Increases of postoperative intraocular pressure at one hour averaged 3.5 +/- 5.1 mm Hg, with an increase of more than 10 mm Hg in three eyes (16.7%), and a maximum of 12 mm Hg, We observed no corneal or retinal damage. CONCLUSION: The picosecond Nd:YLF laser seems to be an effective instrument for reliably performing peripheral iridotomie s of precise size and shape using low energy per pulse levels. This la ser, unlike the argon laser, is successful independent of iris thickne ss or color and can easily make a larger iridotomy than is often possi ble with the Nd:YAG laser.