Purpose: To investigate and compare the long-term safety, efficacy, and accuracy of PRK (photorefractive keratectomy) and LASEK (laser epithelial keratomileusis) in myopic corneas having residual corneal thickness less than 400 micron meters (mu m). Methods: The medical reports of the patients who had undergone excimer laser surface ablation between 2007-2011 and had a residual corneal thickness less than 400 mu m were retrospectively reviewed. Results: Forty-two eyes of 42 patients with a mean age of 28.79 +/- 7.76 years were enrolled into the study. Twenty-two PRK and 20 LASEK procedures were performed. The mean follow-up time was 45.00 +/- 11.80 months. At the end of follow-up, no ectasia was detected. Nineteen percent of eyes had trace haze. No eyes lost any lines in corrected distance visual acuity. Eighty-one percent of the patients had an uncorrected distance visual acuity better than 20/40. The regression rate was 16.7%. Sixty-two percent of eyes were within +/- 1.00 D. The safety and efficacy indexes were 1.19 +/- 0.42 and 1.00 +/- 0.40, respectively. There was not any difference between LASEK and PRK regarding achieved spherical equivalent refraction, haze ratio, visual acuity, safety, efficacy, and regression. Conclusions: Both PRK and LASEK are safe and effective in myopic corneas having thin residual thickness.