Laser in situ keratomileusis for residual myopia after photorefractive keratectomy

Abstract

Purpose: To evaluate the efficacy and safety of laser in situ keratomileusis (LASIK) for myopic regression and undercorrection after photorefractive keratectomy (PRK).Setting: The Eye Institute, Sydney, Australia.Methods: Fifty eyes of 32 patients were treated by LASIK for residual myopia following primary PRK. The mean spherical equivalent refraction (SEQ) was −2.92 diopters (D) ± 1.57 (SD) (range −0.75 to −7.88 D). The mean refractive cylinder was 0.96 ± 0.74 D (range 0 to 3.50 D). For analysis, the eyes were divided into 2 groups: those with 0 or low corneal haze (Group 1) and those with severe corneal haze (Group 2). In Group 1, the SEQ was −1.99 ± 0.79 D (range −0.75 to −3.75 D) and in Group 2, −3.77 ± 1.62 D (range −0.75 to −7.90 D). The procedure was performed using the Chiron Automated Corneal Shaper® and the Summit Apex Plus® laser. The mean interval between PRK and LASIK was 25 months (range 9 to 59 months). The following parameters were studied before and after LASIK retreatment: SEQ, mean refractive cylinder, uncorrected visual acuity (UCVA), and best corrected visual acuity (BCVA). Complications after LASIK retreatment were evaluated.Results: Six months after LASIK, the mean SEQ in all eyes was −0.65 ± 0.86 D (range +1.50 to −3.35 D); 70.0% of eyes were within ±1.00 D of emmetropia and the UCVA was 6/12 or better in 72.5%. The mean SEQ in Group 1 was −0.22 ± 0.55 D (range −0.88 to −1.50 D) and in Group 2, −0.97± 0.92 D (range 0.12 to −3.25 D); the UCVA was 6/12 or better in 94.0% of eyes in Group 1 and in 56.0% in Group 2. No statistically significant between-group difference was found in lines of Snellen acuity lost or gained at 6 months. No eye lost more than 1 line of BCVA.Conclusions: Laser in situ keratomileusis appears to be a safe, effective, and predictable procedure for treating eyes with 0 or low haze with residual myopia after PRK. It is less predictable in eyes with severe haze.