Aims: Investigation of corneal parameters and regularity in the setting of laser in situ keratomileusis (LASIK) using a femtosecond laser and a microkeratome.

Settings and Design: This was a prospective, randomized, paired-eye comparative study.

Subjects and Methods: Ninety-six eyes of 46 patients underwent bilateral LASIK. In each patient, one eye was randomly treated with the femtosecond laser and the other eye with the microkeratome. The central evaluation was based on corneal irregularity, higher-order root mean square (HO-RMS), and other corneal parameters.

Statistical Analysis Used: IBM^® SPSS Statistics version 22.0.0.0 was used to analyze the data and determine the statistical evidence.

Results: At each follow-up time point, the irregularity index for the femtosecond laser group was stable within the 3-and 5-mm zones (P = 0.596 and P = 0.139, respectively), while it was unstable in the microkeratome group (P = 0.03 and P = 0.047). Regarding the HO-RMS, there was no statistically significant difference (P = 0.493) before surgery. After 3 months, there was an increase in HO-RMS in the femtosecond laser group from 0.401 ± 0.179 (range: 0.11–0.89) to 0.423 ± 0.152 (range: 0.17–0.88), which was not significant (P = 0.079). In the microkeratome group, the HO-RMS increased from 0.415 ± 0.175 (range: 0.13–0.94) to 0.573 ± 0.242 (range: 0.13–0.94) which is significant (P < 0.001). The difference in HO-RMS after 3 months between the groups was also significant (P < 0.001).

Conclusions: The femtosecond laser induces significantly less corneal irregularities and less HO-RMS compared to a microkeratome. This potentially leads to better quality of visual acuity in the femtosecond group and better predictability.