Comparative clinical outcomes of SMILE, femtosecond LASIK, and transepithelial PRK: a multicenter Iraqi study.

PURPOSE: To compare refractive predictability, long-term stability, visual quality, ocular surface outcomes, and safety of small incision lenticule extraction (SMILE), femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK), and transepithelial photorefractive keratectomy (Trans-PRK) for myopia correction in an Iraqi population.

METHODS

This retrospective multicenter comparative cohort study included 919 eyes of 919 patients who underwent SMILE (388 eyes), FS-LASIK (344 eyes), or Trans-PRK (187 eyes) between January 2023 and December 2025. Postoperative outcomes were evaluated at 6 months, 1 year, and 1.5 years. Primary outcome measures included refractive predictability and stability of spherical equivalent (SE). Secondary outcomes included uncorrected and corrected distance visual acuity (UDVA and CDVA), absolute refractive error, induced corneal higher-order aberrations (HOAs) at 6 months, Ocular Surface Disease Index (OSDI) scores, and safety outcomes. Multivariable linear regression analysis was performed to identify factors associated with residual SE at 1.5 years.

RESULTS

SMILE demonstrated the highest refractive predictability and long-term stability, with postoperative SE values closest to emmetropia and the narrowest distribution of residual refractive error at all follow-up intervals. FS-LASIK showed intermediate outcomes, whereas Trans-PRK was associated with greater residual myopia and increased refractive regression over time. Induced corneal HOAs were lowest following SMILE and highest following Trans-PRK. OSDI scores were consistently lower after SMILE, intermediate after FS-LASIK, and highest after Trans-PRK throughout follow-up. Multivariable analysis identified surgical technique as the primary independent predictor of residual SE at 1.5 years, with FS-LASIK and Trans-PRK associated with significantly greater myopic residual error than SMILE. All three procedures demonstrated a high safety profile, with low rates of CDVA loss and infrequent enhancement procedures.

CONCLUSIONS

In this large multicenter Iraqi cohort, SMILE provided superior refractive predictability, long-term stability, visual quality, and ocular surface outcomes compared with FS-LASIK and Trans-PRK. FS-LASIK remained an effective and safe alternative, while Trans-PRK was associated with greater refractive regression and higher enhancement rates, particularly in eyes with higher degrees of myopia. These findings support procedure-specific patient selection to optimize refractive outcomes and postoperative comfort.