Femtosecond laser versus mechanical keratome LASIK for myopia

Abstract

Objective: To assess efficacy, safety, predictability, stability, and changes in corneal higher-order aberrations (CHOAs) and contrast sensitivity (CS) after a femtosecond laser for LASIK and standard LASIK for myopia.

Design: Prospective, randomized, comparative clinical study.

Participants: Two hundred eyes of 100 consecutive patients who underwent LASIK treatment using the VISX S2 laser system. A femtosecond laser for flap creation was used in 100 eyes (50 patients; spherical equivalent [SE], -2.85+/-1.79 diopters [D]), and a mechanical microkeratome was used in 100 eyes (50 patients; SE, -2.90+/-1.63 D).

Methods: Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, CS by means of the Functional Acuity Contrast Test, and CHOAs by means of custom software linked to topography were evaluated preoperatively and 6 months after treatment.

Main outcome measures: Efficacy, safety, predictability, stability, CHOAs, and CS were evaluated before and after surgery at 6 months' follow-up.

Results: At 6 months postoperatively, UCVA was 1.0 or better in 100% of the eyes. Efficacy indexes were 1.07 for the femtosecond laser for LASIK patients and 1.00 for LASIK patients. No eye lost > or =1 lines of BCVA; for the femtosecond laser for LASIK group, 24 eyes gained 1 line, and 18 eyes gained > or =2 lines; for the LASIK group, 18 eyes gained 1 line. The femtosecond laser for LASIK group showed a percentage of eyes (98%) within the 0.5-D range in SE higher than that of the LASIK group (92%). For a 3.5-mm pupil, CHOAs' root-mean-square (RMS) increased for both the femtosecond laser for LASIK (2.21-fold) and LASIK (2.81-fold) groups. For a 6-mm pupil, CHOA RMSs were increased significantly after femtosecond laser for LASIK (4.18-fold) and LASIK (5.07-fold) surgeries (P<0.01). Contrast sensitivity improved only in the femtosecond laser for LASIK group at the highest spatial frequency (18 cycles/degree; P<0.01) after surgery.

Conclusions: A femtosecond laser for LASIK surgery is an effective and, in this series, safe procedure for treatment of myopia. The improvements in UCVA and CS after the femtosecond laser for LASIK are related to the differences in postoperative CHOAs found with femtosecond and microkeratome flap creation.