Evaluation of photorefractive keratectomy retreatments after regressed myopic laser in situ keratomileusis

Purpose: To evaluate the results of photorefractive keratectomy (PRK) enhan cements in eyes previously treated by myopic laser in situ keratomileusis ( LASIK) showing an undercorrection due to either a refractive regression or a primary undercorrection, when an in-the-bed enhancement was not advisable because of residual stromal thickness limitations. Design; Noncomparative, prospective, interventional case series. Participants: Seventeen eyes of 17 patients previously treated by LASIK for a spherical equivalent (SE) correction of -8.125 to -12.50 diopters (D; me an, -9.45 +/- 1.01 D), that after a follow-up of 6 to 14 months ended up wi th a refraction of -1.50 to -3.75 D (SE; mean, -2.48 +/- 0.74 D). Intended flap thickness was 160 gm for all eyes. In all cases, the residual stromal bed under the flap was considered too thin (255-305 mum) to allow an in-the -bed enhancement without exceeding an assumed safety thickness limit (250 g m). Intervention: Eyes were treated by PRK at least 6 months after LASIK The PR K ablation parameters (diameter, attempted correction) were selected to avo id theoretical flap perforation. The deepest ablation was 60 mum, for a -3. 75-D correction. We used a Bausch & Lomb 217 C excimer laser (Bausch & Lomb , Rochester, New York). Main Outcome Measures. Refraction, uncorrected and best-corrected visual ac uity (BCVA), slit-lamp evidence of corneal opacity or other visible complic ations, and corneal topography. Results: Although the initial postoperative period was characterized by ver y satisfactory refractive results (mean SE error at 1 month, -0.04 +/- 0.37 D; range, +0.75 to -0.625 D), during follow-up, a dense haze (grade 3 and 4) developed in 14 eyes (82.3%) that induced a further myopic regression (S E, -1.725 to -5.50 D; mean, -3.11 D) and BCVA loss (two to six lines). Thes e 14 eyes underwent a further surgical treatment to remove the severe haze at 3 to 10 months after PRK Conclusions: Based on these results, we strongly advise against PRK as a po ssible option to correct eyes previously treated by myopic LASIK that resul ted in an undercorrection. Ophthalmology 2001;108:1732-1737 (C) 2001 by the American Academy of Ophthalmology.