Comparison Of Long-Term Changes In The Effective Optical Zone Following Smile And Fs-Lasik For Moderate To High Myopia

The effective optical zone (EOZ) is closely related to postoperative visual quality, but its long-term changes have remained unclear. This study aimed to compare long-term changes in the EOZ following small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for moderate and high myopia.

Eye and ENT Hospital of Fudan University, Shanghai, China.

This study enrolled 72 eyes of 42 patients, including 36 eyes (mean spherical equivalent (SE): -7.29 ± 1.15 D) who underwent SMILE and 36 eyes (mean SE: -7.50 ± 1.70 D) who underwent FS-LASIK. Preoperative, 3-year and 7-year postoperative examinations included refractions, visual acuity, intraocular pressure, and corneal topography. EOZ was calculated using custom software that automatically distinguishes EOZ on the tangential curvature difference map of the Pentacam HR. The difference in EOZ between SMILE and FS-LASIK, the difference between EOZ and the programmed optical zone (POZ), and its relationship with corneal aberrations, surgical parameters and topographic parameters were evaluated.

The respective EOZ was 5.13 ± 0.27 mm and 4.70 ± 0.24 mm after SMILE and FS-LASIK (P < 0.001) at 3 years postoperatively, and 5.03 ± 0.28 mm and 4.63 ± 0.23 mm at 7 years postoperatively (P < 0.001). EOZ in both groups decreased over time (both P < 0.05). EOZ/POZ in both groups was negatively correlated with the increase in the spherical aberration at both 3 and 7 years postoperatively (P < 0.05) and was positively related to corrected spheres and negatively correlated with ∆Q-value (P < 0.05) at 3 years postoperatively. EOZ/POZ after SMILE was negatively correlated with ∆Q-value (β = -5.120, P = 0.009); and EOZ/POZ after FS-LASIK was negatively correlated with the corrected cylinders (β = -1.211, P = 0.004) at 7 years postoperatively.

EOZ after SMILE was significantly larger than that after FS-LASIK in the long postoperative term. The EOZ continued constricting after both types of surgeries. Long-term changes in the EOZ following both surgeries were related to spherical aberration and may possibly affect the long-term visual quality of patients with moderate to high myopia.