Neodymium-YAG laser sclerostomy in primates.

A one-stage sclerostomy procedure was performed "noninvasively" in four cynomolgus monkeys solely with the neodymium-YAG laser. The neodymium (Nd)-YAG laser was focused, for the most part, a few diopters behind the focus of the helium-neon aiming beam. This enabled optical breakdown to occur entirely within the sclera to produce a perforating micropuncture of the scleral tissue. Two monkeys were treated with higher energy (23 and 24 joules) and two were treated at lower energy levels (12 and 14 joules). An immediate reduction of intraocular pressure in the treated eye was associated with a significant increase in outflow facility. The sclerostomy remained patent for more than 180 days, as determined by tonography and histologic examination. Scanning electron microscopic examination of the cornea revealed no significant damage to the central cornea or to tissue adjacent to the visual axis in any of the treated eyes. However, there was some endothelial cell loss at the site of the laser treatment at the peripheral cornea and in the area immediately posterior to the incision; there was also a focal break in Descemet's membrane.