Thin flap laser in situ keratomileusis: analysis of contrast sensitivity, visual, and refractive outcomes.

ABSTRACT

PURPOSE: To analyze refractive, visual, and contrast sensitivity outcomes of laser in situ keratomileusis (LASIK) performed under thin flaps (less than 100 microm), and compare them with those of conventional thicker flaps. SETTING: Clínica Baviera, Instituto Oftalmológico Europeo, Madrid, Spain. METHODS: This retrospective study comprised 280 consecutive eyes that had LASIK for myopia using the Moria LSK-One microkeratome and the Technolas 217C excimer laser. Efficacy, predictability, and contrast sensitivity indicators were compared between 3 groups of flap thickness thin (<100 microm, n = 105), medium (100 to 129 microm, n = 122), and thick (>130 microm, n = 53). RESULTS: Refractive results were excellent and comparable between the 3 groups; however, visual outcomes-measured as efficacy, postoperative evolution of uncorrected visual acuity, and contrast sensitivity-test were significantly better in the thin flap group. Efficacy results were 92.9%, 91.0%, and 81.0% in the thin, medium, and thick flap groups, respectively (P < .05), and the rate of enhancements was 0%, 2.3%, and 5.6%, respectively. With regard to contrast sensitivity, changes between preoperative and postoperative values at month 3 of follow-up, the thin flap group achieved the preoperative levels at 3 spatial frequencies (3, 6, and 18 cycles per degree), while the thicker flap groups maintained lower than preoperative levels at more than 2 spatial frequencies. When comparing contrast sensitivity values between the 3 groups, the thin flap group also obtained the best results at lower spatial frequencies. CONCLUSIONS: Thin flap LASIK is a safe technique to correct myopic defects since it blends the advantages of surface and lamellar procedures (minimal debilitation of corneal biomechanical architecture with the rapid and comfortable visual recovery of lamellar approaches). Moreover, it achieves excellent refractive outcomes, a lower rate of enhancements, and a good visual performance with better contrast sensitivity test results.