Comparison of early postoperative dry eye after KLEx and FS-LASIK: a contralateral eye study

To compare early postoperative dry eye outcomes in contralateral eyes of the same patients undergoing Keratorefractive Lenticule Extraction (KLEx) versus Femtosecond Laser-Assisted Laser In Situ Keratomileusis (FS-LASIK), with tear film osmolarity defined as the primary outcome measure.

This study was conducted at Dunyagoz Izmır Hospital and involved patients who underwent corneal refractive surgery between June 2021 and December 2024. Patients with pre-existing dry eye disease were excluded from the study. Patients underwent KLEx in one eye and FS-LASIK in the fellow eye. Tear film osmolarity (primary outcome) was measured preoperatively and postoperatively using the TearLab^® system. Secondary outcome measures included tear break-up time (tBUT) and subjective symptoms assessed via the Ocular Symptom Questionnaire Scores (OSDI).

A total of 34 eyes of 17 patients (7 females and 10 males) were evaluated. Group 1 (KLEx) included 17 eyes and group 2 (FS-LASIK) included contralateral 17 eyes. The mean postoperative follow-up period was 34.2 days. Mean tear osmolarity was 297.7 ± 8.3 mOsm/L in the group 1 and 315.3 ± 10.2 mOsm/L in the group 2 (p < 0.001). Mean tBUT was 10.3 ± 3.1 s for group 1 and 7 ± 2.32 s for group 2 (p < 0.001). The mean postoperative OSDI scores were 32.5 for group 1 and 42 for group 2, with a preoperative baseline of 10.2 (both groups; p < 0.001).

KLEx demonstrated superior early postoperative ocular surface stability compared to FS-LASIK in contralateral eyes. The procedure resulted in significantly less tear hyperosmolarity and better subjective comfort, suggesting it may be a preferable surgical option for minimizing dry eye induced by corneal refractive surgery.