Clinical experience of two-step photorefractive keratectomy in 19 eyes with high myopia

The maximum myopic correction with one-step ablation in excimer laser photorefractive keratectomy (PRK) using the ExciMed UV200 LA 193-nanometer excimer laser (Summit Technology, Inc, Waltham, Mass,) is only up to 6.00 D because of a fixed computer program. We performed a simultaneous two-step PRK procedure for nearly full correction on 19 eyes of 19 patients with myopia ranging from -8.00 to -13.50 D. We clinically evaluated the results of this modified technique at 6 months, or more, after surgery. In the two-step PRK procedure, we attempted in the first-step of a maximum correction of -6.00 D (including up to -7.50 D) with 4.5-millimeter ablation zone. The second step was performed immediately thereafter to correct the remaining myopia with a 5.0-millimeter diameter ablation. Mean preoperative manifest refraction was -9.77, D and mean postoperative manifest refraction was -1.09 D at 6 months after two-step PRK. Uncorrected visual acuity of 20/40 or better was achieved in 74% of 19 eyes (two were amblyopic eyes). Corneal subepithelial haze was trace or +1 in all cases at 3 months, but faded out after 3 months. Transient intraocular pressure elevation occurred in one case. No other significant complications developed. Long-term follow up will be required to evaluate the results of two-step PRK.