Use of the neodymium:YAG laser to create iridotomies in monkeys and humans.

In a prospective study the Nd:YAG laser was used to create iridotomies in cynomolgus monkeys, using various levels of energy and pulse-trains of 1 to 9. Although no change occurred in the endothelial cell count of the cornea, opacities of the corneal endothelium and lens did occur. In addition, one eye showed rupture of the anterior lens capsule immediately behind the iridotomy. Most of the iridotomies in these animals closed within 3 to 4 weeks. Attenuated pigment epithelium bridged the gap within 9 days and in many sections it appeared that the iridotomies closed by fibrous contraction or early stromal regeneration. A prospective short-term clinical study evaluated argon and Q-Nd:YAG laser iridotomies in 42 eyes of 21 patients with primary chronic angle-closure glaucoma. In each patient one eye was randomly treated with an argon laser iridotomy and the fellow eye with a Nd:YAG laser iridotomy. In every case a patent iridotomy was created in one session. A mean of 12 +/- 11 and 0.033 +/- 0.025 Joules was required to complete an iridotomy with the argon and Nd:YAG lasers, respectively. Thirty percent of the argon iridotomies became sufficiently closed with pigment to require retreatment; whereas none of the Nd:YAG iridotomies closed. A postoperative rise in IOP greater than 10 mm Hg was seen in 38% argon- and 29% Nd:YAG-treated eyes. Although bleeding around the iridotomy occurred in 48% of eyes, in no case was this of significant consequence. No acute lens damage was observed in the Nd:YAG-treated human eyes, while 43% of lenses in the argon group had focal opacities. Thirty-three percent of Nd:YAG- and 24% of argon-treated eyes had focal, nonprogressive corneal opacities above the iridotomy. Specular microscopy showed a significant central corneal epithelial cell loss in argon laser eyes only. The potential of creating a laser iridotomy with a single burst of energy is extremely attractive and worthy of further investigation.