SMILE shows superior refractive predictability and stability versus FS-LASIK and Trans-PRK in myopia correction

$SMILE shows superior refractive predictability and stability versus FS-LASIK and Trans-PRK in myopia…$

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Frontiers in Medicine Published April 14, 2026 Medically reviewed April 25, 2026 DOI ↗ By Dr. Lars van Dijk, PhD · Surgical, Procedural & Diagnostic

Key Takeaway

Consider SMILE's potential advantages in refractive outcomes and comfort, but note observational limitations.

This retrospective multicenter comparative cohort study evaluated 919 eyes of 919 Iraqi patients undergoing myopia correction with SMILE, FS-LASIK, or Trans-PRK. The study assessed refractive predictability and stability of spherical equivalent (SE) as the primary outcome, with secondary outcomes including uncorrected and corrected distance visual acuity, absolute refractive error, induced corneal higher-order aberrations (HOAs), Ocular Surface Disease Index (OSDI) scores, and safety outcomes over follow-up periods of 6 months, 1 year, and 1.5 years.

Results showed SMILE demonstrated the highest predictability and stability with postoperative SE values closest to emmetropia and the narrowest distribution of residual refractive error. 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. Surgical technique was identified 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. No serious adverse events, discontinuations, or tolerability issues were reported. Key limitations include the retrospective observational design, which precludes causal conclusions, and lack of reported effect sizes, absolute numbers, p-values, or confidence intervals for most outcomes. Funding and conflicts of interest were not reported.

For clinical practice, these findings support procedure-specific patient selection to optimize refractive outcomes and postoperative comfort, but clinicians should interpret results cautiously given the observational nature and limited statistical reporting. Multivariable linear regression analysis identified surgical technique as the primary independent predictor, but prospective randomized trials are needed to confirm these associations.

Study Details

Study typeCohort

EvidenceLevel 3

PublishedApr 2026

View Original Abstract ↓

PurposeTo 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.MethodsThis 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.ResultsSMILE 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.ConclusionsIn 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.