Two-year observation of posterior corneal elevations after small incision lenticule extraction (SMILE) for myopia higher than −10 dioptres

Abstract

AimTo investigate the change in posterior corneal elevations (PCEs) of eyes with extremely high myopia 2 years after small incision lenticule extraction (SMILE).MethodsWe evaluated 39 eyes of 39 patients with spherical equivalent higher than −10.00 dioptres (D). Using a Scheimpflug camera (Pentacam), we measured change in PCEs at 1 day, 3 months, 6 months and 2 years after SMILE. Another 34 eyes of 34 patients who underwent femtosecond laser-assisted in situ keratomileusis (FS-LASIK) were examined before, at 1 day and long-term after surgery as the control group. For each eye, elevations at central, thinnest, maximal points and 24 other predetermined points were measured.ResultsNo significant forward displacements of PCEs were observed in both surgeries. The maximal but not significant forward displacement occurred around 3–6 months following SMILE, and all returned to original levels 6 months postoperatively except superior area. The peripheral area tended to displace backward, while the central area tended forwardly. In both procedures, elevations along horizontal meridians, inferior and temporal hemispheres were significantly higher than those along vertical meridians, superior and nasal hemispheres, respectively (p<0.05). Elevation on the 4 mm, 6 mm diameters at 1 day and on the 6 mm diameter and temporal hemisphere at long-term follow-up postoperatively were significantly higher in FS-LASIK than SMILE (p<0.05). Change in elevations on the 6 mm diameter circle correlated with residual bed thickness (p=0.047).ConclusionsSMILE is a safe way to correct for myopia higher than −10 D, with PCEs remaining stable 2 years after surgery.

Clinical outcomes after small incision lenticule extraction versus femtosecond laser-assisted LASIK for high myopia: a Meta-analysis.

“…We found Change in PCE has statistical significance only at long term follow-ups, there was no significant difference between the two groups at 3-or 6-months post operation. Many studies [2,14,19] have reported similar results and provide complementary evidence for high myopia. Although the FS-LASIK procedure has been optimized by the femtosecond laser in past 10 years, complications relating to the corneal flap still occur in an otherwise perfect FS-LASIK [25] .…”

“…Guofu Chen [ Cylinder :-0.66±0.7 0 (≥−6.00) Yueming Zhou [18] 2016 CT Chinese 66 7.58±2.14 (-6.125 ~ -9.75) Xueyi Zhou [19] 2019 CT English 39 −10.79±0.81 (-10.00~−13.00)…”

“…Then except for 12 duplicate reports, 67 papers underwent title and abstract screening.33 studies were excluded as a result of following reasons: 11 studies did not have control group, and just made a separate description of SMILE or FS-LASIK; and 7 studies' control groups were not SMILE and FS-LASIK; meanwhile there were 15 Studies whose subjects were not high myopia. Finally, there remained 10 studies [2,3,11,[14][15][16][17][18][19][20] that met our inclusion criteria and they were included in this meta-analysis. Table 1 summarized the main characteristics and the quality assessment of these 10 included studies, which were published from 2014 to 2019.…”

“…CI:-0.04 to 0.00, I²=98%, P=0.40, Figure 8) Biomechanical effects PCE change. There are 2 include studies [2,19] described the change in PCE, and the change in PCE at 3, 6 and long term post operation for high myopia are shown in Figure 9A. At 3 and 6 months post operation, no significantly difference was found in the PCE change between the two groups(WMD =-0.19, 95% CI:-0.41 to 0.03, I²=31%, P=0.09;WMD =-0.20, 95% CI:-0.50 to 0.10, I²=17%, P=0.20, Figure 9A).…”

“…At 3 and 6 months post operation, no significantly difference was found in the PCE change between the two groups(WMD =-0.19, 95% CI:-0.41 to 0.03, I²=31%, P=0.09;WMD =-0.20, 95% CI:-0.50 to 0.10, I²=17%, P=0.20, Figure 9A). By long term observation(Bingjie Wang [2] :1 year; Xueyi Zhou [19] :2 years), PCE change was significantly greater in the FS-LASIK group than the SMILE group (WMD =-0.69, 95%…”