Excimer laser in situ keratomileusis to correct compound myopic astigmatism

Abstract

Purpose: We studied the efficacy, predictability, stability, and safety of excimer laser in situ keratomileusis (LASIK) to correct myopia and astigmatism.

Methods: We prospectively studied 87 consecutive eyes of 56 patients who received LASIK, divided into two groups: the myopic group included eyes with myopia more than -2.00 diopters (D) and astigmatism less than 0.50 D and the astigmatism group included eyes with myopia of more than -2.00 D and astigmatism of 0.50 D or more. The Chiron automated corneal shaper and the Nidek EC-5000 excimer laser were used in all eyes. A modified personal nomogram was used in all eyes. The changes in refractive sphere and cylinder, and complications were studied at 2 and 6 weeks, 3, 6, and 12 months after surgery. Preoperatively, the mean spherical equivalent refraction was -4.41 D (range, -2.25 to -7.25; SD, 1.74) in the myopia group and -5.79 D (range, -2.25 to -15.50 D; SD, 2.45) in the astigmatism group. The mean spherical component of the refraction was -4.39 D (range, -2.25 to -7.25; SD, 1.74) in the myopia group and -5.19 D (range, -2.00 to -14.00; SD, 2.32) in the astigmatism group. The mean refractive cylinder was 1.19 D (range, 0.5 to 3.00 D; SD, 0.62) in the astigmatism group.

Results: At 12 months, 81 eyes (93.6%) of 51 patients were examined; the mean spherical equivalent refraction was -0.43 D (range, +0.50 to -1.25 D; SD, 0.35) in the myopia group and -0.33 D (range, +1.25 to -2.13 D; SD, 0.52) in the astigmatism group. The mean spherical component of the refraction at 12 months was -0.33 D (range, +0.50 to -1.25 D; SD, 0.33) in the myopia group and -0.17 D (range, +1.50 to -1.50; SD, 0.48) in the astigmatism group. The mean refractive cylinder was 0.19 D (range, 0 to 0.75 D; SD, 0.25) in the myopia group and 0.32 D (range, 0 to 1.25 D; SD, 0.30) in the astigmatism group. The mean change in spherical equivalent refraction between 6 weeks and 12 months after surgery was -0.08 D toward myopia (range, -0.50 to -0.75 D; SD, 0.23) in both groups. No eyes lost two or more lines of spectacle-corrected visual acuity. Patient satisfaction was high in both groups. Complications included undercorrection that necessitated reoperation (three eyes), overcorrection (two eyes), and small disc diameter (one eye). No vision threatening complications were observed.

Conclusion: LASIK with the Nidek EC5000 laser is effective, reasonably predictable, stable, and safe for correction of compound myopic astigmatism with a spherical component between -2.00 and -14.00 D, and a cylindrical component between 0.50 and 3.00 D using the techniques in this study. Astigmatism is undercorrected with the current algorithm. Correction of higher amounts of astigmatism requires further study.