Photorefractive keratectomy in 472 eyes

Between July 1990 and July 1992, 472 eyes were treated with photorefractive keratectomy (PRK) using the ExciMed UV200 193-nanometer excimer laser (Summit Technology, Inc, Waltham, Mass). The sphere equivalent refractions ranged between -1.25 and -9.60 D, with less than 1.25 D of astigmatism. Eyes with refractive error up to -6.00 D were treated with a spherical ablation, as determined by the surgeon's decision and the algorithm built into the laser software. In this group, 92% had a refraction within 1.00 D of intended correction. Eyes with more than -6.00 D of myopia were treated with a dual-zone procedure, using a nomogram developed by the author. After 6 months, 45% of eyes had a refraction within +/- 1.00 D, and 84% were within +/- 2.00 D of emmetropia. Excimer PRK up to -6.00 D is safe and predictable; above -6.00 D it is less predictable.