Safety and stability of laser in situ keratomileusis for myopic correction performed under thin flaps

To determine the safety and long-term refractive stability of laser in situ keratomileusis (LASIK) performed under thin flaps (<110 microm) and to compare them with those of conventional thicker flaps (>110 microm).

This retrospective study consisted of 120 myopic eyes of 68 patients who underwent LASIK performed with the use of the Moria M2 microkeratome and the Technolas Keracor 117C excimer laser. Indicators of efficacy, predictability, and long-term stability were followed for 1 year after surgery and were compared among 3 groups of patients that varied according to the flap thickness used: thin (<110 microm, n = 29), medium (111-139 microm, n = 47) and thick (>140 microm, n = 44).

One year after myopic LASIK, the mean spherical equivalent refraction for the thin-flap group A was -0.37 (standard deviation [SD] 0.44) diopters (D); medium-flap group B was -0.48 (SD 0.55) D; and thick-flap group C was -0.43 (SD 0.45) D. The percentage of eyes with spherical equivalent refraction within SD 0.50 D and SD 1.00 D of emetropia was 84% and 92% for group A, 82% and 91% for group B, and 79% and 90% for group C, respectively. Buttonholes were encountered in 3% of eyes in group A compared with 0% in the other 2 groups. Epithelial ingrowth and peripheral flap striae occurred in 7% and 7% in group A, 2% and 2% in group B, and 2% and 0% in group C, respectively.

Thin-flap LASIK (<110 microm) produces more intra- and early post-operative complications compared with thick-flap LASIK (>110 microm). However, if a thin flap is created and there are no complications, or if the complications are successfully managed, there does not appear to be any difference in the long-term refractive results.