Evaluation Of Corneal Morphology And Ocular High Order Aberrations After Bilateral Sequential Small-Incision Lenticule Extraction And Laser Epithelial Keratomileusis For Low To Moderate Myopia: A 4-Year Comparative Study

The purpose of this study is to evaluate corneal morphology and ocular high order aberrations following bilateral sequential small incision lenticule extraction (SMILE) and laser epithelial keratomileusis (LASEK) for the correction of low myopia over a four-year duration.

Although the efficacy and safety of small incision lenticule extraction (SMILE) for myopia correction have been confirmed since its introduction in 2011, there is currently no evidence available on long-term comparisons of corneal morphology and ocular high-order aberrations between SMILE and LASEK for low to moderate myopia correction.

Two cohorts were enrolled in this retrospective study at the Shanghai Tenth People’s Hospital affiliated to Tongji University between October 2017 and May 2018, comprising of 30 low to moderate myopic patients who underwent bilateral SMILE and LASEK procedures, resulting in a total of 30 eyes in each group. Comprehensive ophthalmic examinations were conducted before and four years after surgery. The main outcomes, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent, central corneal thickness, corneal Fourier components, and ocular wavefront aberrations were evaluated for comparative analysis between the two cohorts.

Four years after surgery, the UDVA exceeded 20/16 in 73.33% and 100% of the eyes in the SMILE and LASEK groups, respectively. The anterior corneal asymmetry increased in both groups, whereas the anterior regular astigmatism (RA) decreased in the LASEK group. LASEK induced a notable elevation in posterior corneal high-order irregularity, posterior RA, and total corneal asymmetry, whereas total corneal RA and spherical component showed a significant reduction. In addition, ocular vertical coma, horizontal coma, spherical aberration, and high-order aberration demonstrated a significant increase in the SMILE group. Compared with the SMILE group, higher ocular horizontal coma and lower vertical coma were observed in the LASEK group.

The efficacy, safety, and stability of both SMILE and LASEK have been demonstrated in correcting low to moderate myopia. In comparison to SMILE, LASEK results in a greater reduction in regular astigmatism, flatter anterior and total corneal curvature, and minimal change in the posterior surface of the cornea. However, four years post-surgery, SMILE induces higher vertical coma aberration and lower horizontal coma aberration compared to LASEK.