Oram O, Gross R L, Severin T D, Orengo-Nania S, Feldman R M
Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030, USA.
Am J Ophthalmol. 1995 Apr;119(4):408-14. doi: 10.1016/s0002-9394(14)71225-5.
We evaluated the picosecond neodymium:yttrium lithium fluoride (Nd:YLF) laser for performing peripheral iridotomies of predetermined size and shape in various types of irides.
In the first part 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.
In the cadaver eyes, the optimal parameters were a rectangular cutting pattern of 0.3 x 0.3 mm, 500-microns cutting depth, 50-microns spot separation, 200 to 400 microJ of energy per pulse, 200 to 400 pulses per second, and no focal offset distance. In 18 eyes of 11 patients, iridotomies with well-defined margins and size were created. Minimal hemorrhage occurred intraoperatively in ten of 18 eyes (55.6%), which did not affect the outcome of the procedure. 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.
The picosecond Nd:YLF laser seems to be an effective instrument for reliably performing peripheral iridotomies of precise size and shape using low energy per pulse levels. This laser, unlike the argon laser, is successful independent of iris thickness or color and can easily make a larger iridotomy than is often possible with the Nd:YAG laser.
