Comparison of the Functional Optical Zone in Eyes With High Myopia With High Astigmatism After SMILE and FS-LASIK

Abstract

PURPOSE: To compare the functional optical zone (FOZ) in eyes with high myopia with high astigmatism after small incision lenticule extraction (SMILE) and femtosecond laser–assisted laser in situ keratomileusis (FS-LASIK). METHODS: In total, 45 eyes of 45 patients with high myopia with astigmatism greater than 2.00 diopters (D) who underwent SMILE or FS-LASIK were enrolled. The FOZ, optical zone decentration, and corneal aberrations were analyzed using Scheimpflug imaging. These values were then compared between the two groups 6 months postoperatively. RESULTS: No postoperative complications were observed during follow-up. The mean FOZ diameter was 5.03 ± 0.31 mm for the FS-LASIK group and 5.24 ± 0.27 mm for the SMILE group ( P = .007), corresponding to reductions of 1.18 ± 0.23 and 1.01 ± 0.21 mm, respectively, compared with the programmed optical zone (POZ) ( P = .013). A significant difference was noted in the FOZ on the short axis between the two groups ( P = .002), whereas no significant difference was observed on the long axis ( P = .088). The FOZ area in the FS-LASIK and SMILE groups was 65.39 ± 6.14% and 70.09 ± 5.46% of the POZ area, respectively ( P = .010). There was no significant difference in decentration between the two groups (0.29 ± 0.13 mm for the FS-LASIK group vs 0.30 ± 0.13 mm for the SMILE group, P = .798). A significant increase in spherical aberration was observed in the FS-LASIK group ( P < .001). However, the induction of vertical coma was higher in the SMILE group than in the FS-LASIK group ( P = .002). CONCLUSIONS: Eyes with high myopia with high astigmatism following SMILE achieved a larger FOZ and less spherical aberration but a larger vertical coma introduction than following FS-LASIK. [ J Refract Surg . 2022;38(9):595–601.]

Effective Optical Zone Diameter, Decentration and High-Order Aberrations Following LIKE in Correcting Moderate to High Hyperopia

“…Previously, the method commonly used to analyze the EOZ diameter was the average gured by manual multi-radial measurement [9,12]. This method may be limited by low measurement e ciency and poor repeatability.…”

Correlational Analysis of the Effective Optical Zone with Myopia, Myopic Astigmatism, and Spherical Equivalent in LASIK, PRK, and SMILE

“…Twelve points where a 0 D difference was detected between the pre-and post-scans were measured at every consecutive 30 degrees moving counterclockwise from 0° in order to approximate the EOZ. 11,12,14 Python 3.11 (Python Software Foundation) was used to run the publicly available NumPy best fitting ellipse program, which provides data such as the ellipse's center point, area, axis lengths, and eccentricity. In this study, the major and minor axes are called major and minor diameters, and they denote the transected distance in mm between the two elliptical points that are farthest from, and closest to, each other, respectively.…”

Femtosecond laser-assisted in situ keratomileusis versus small-incision lenticule extraction: current approach based on evidence

“…Wu et al also found SMILE superior to FS-LAIK in uncorrected distance visual acuity and optical quality at postoperative year 1 [25]. SMILE may also have added benefits over FS-LASIK in the high myopia group such as a smaller decrease in functional optical zone (FOZ) [26], a key marker of visual quality [27] and less increase in overall higher order aberration specifically spherical aberration [25,28]. Lastly, SMILE theoretically preserves more corneal stress resistance [29].…”