Changes in the posterior corneal surface after femtosecond laser-assisted lenticule intrastromal keratoplasty (LIKE) performed into a pocket (SMI-LIKE) or under a flap (FS-LIKE).

BACKGROUND: To compare the changes in posterior corneal surface after small-incision lenticule intrastromal keratoplasty (SMI-LIKE) and femtosecond laser-assisted lenticule intrastromal keratoplasty (FS-LIKE) for hyperopia correction. METHODS: In this prospective comparative randomized study, 23 eyes with hyperopia were recruited. Eyes were categorized into two groups-SMI-LIKE group (11 eyes) and FS-LIKE group (12 eyes). Lenticules from myopia small incision lenticule extraction were implanted into a pocket (SMI-LIKE group) or at a depth of 100 µm under a flap (FS-LIKE group). Posterior corneal elevations in the center, mid-periphery, and periphery, as well as mean keratometry of the posterior corneal surface (Kmb) were measured using a Pentacam over a three-month follow-up. RESULTS: All surgeries were completed successfully and no complications occurred. At one day postoperatively, there was a slight backward change with SMI-LIKE and a forward change with FS-LIKE in the central region of the posterior corneal elevation. Conversely, the peripheral area showed forward displacement in SMI-LIKE and an apparent backward change in FS-LIKE. The mid-peripheral regions manifested a backward change after the procedure throughout the entire follow-up in both groups. Kmb exhibited flattening at one month postoperatively and subsequently returned to its original level at three months after SMI-LIKE while in FS-LIKE, Kmb steepened after lenticule implantation with a significant change noted at one day postoperatively (P = 0.001). CONCLUSIONS: Posterior corneal surface after SMI-LIKE and FS-LIKE exhibited different change patterns in various corneal regions, with the most prominent change occurring at one day postoperatively during the three-month follow-up. TRIAL REGISTRATION: Chinese Clinical Trial Registry: ChiCTR-ONC-16008300. Registered on Apr 18th, 2016.  http://www.chictr.org.cn/edit.aspx?pid=14090&htm=4.

Efficacy Comparison Between Steep-Meridian Incision and Non-Steep-Meridian Incision in Implantable Collamer Lens Surgery with Low-to-Moderate Astigmatism.

INTRODUCTION: To compare the visual outcomes of astigmatism correction with implantable collamer lens (ICL) surgery with low-to-moderate astigmatism through a steep-meridian corneal relaxing incision (SM-CRI) and non-steep-meridian corneal relaxing incision (NSM-CRI). METHODS: Seventy eyes of 70 patients with myopia and myopic astigmatism who underwent ICL V4c implantation were classified into two groups: SM-CRI and NSM-CRI. Refractive outcomes and vector analysis were evaluated preoperatively and 6 months postoperatively. RESULTS: At the postoperative 6 month visit, all participants in both groups achieved an uncorrected distance visual acuity (UDVA) of 20/20 or better. The difference vector (DV) showed that the residual astigmatism in the SM-CRI group was much smaller than that in the NSM-CRI group (P = 0.021), and the correction index (CI) was 0.84 ± 0.30 and 0.67 ± 0.35 for the SM-CRI and NSM-CRI groups, respectively, with a significant statistical difference (P = 0.013). Approximately 71% of eyes in the SM-CRI group had an angle of error (AE) within ± 15°, whereas 55% of eyes in the NSM-CRI group were within that range. The absolute mean AE was 10.13 ± 14.57° in the SM-CRI group, compared with 23.88 ± 28.22° in the NSM-CRI group (P = 0.038). CONCLUSION: SM-CRI can alleviate corneal astigmatism and decrease the cylindrical diopter of the ICL, thus improving postoperative visual quality compared with NSM-CRI.

Effect of keratometric astigmatism on visual outcomes following small incision lenticule extraction.

Purpose: To investigate the influence of keratometric astigmatism on visual outcomes following small incision lenticule extraction (SMILE). Methods: Eighty eyes undergoing SMILE for myopia correction were classified into two groups based on preoperative keratometric astigmatism: low keratometric astigmatism (LA) and high keratometric astigmatism (HA) groups. Refractive outcomes, vector components, and changes in higher order aberrations (HOAs) were evaluated preoperatively and 6 months postoperatively. Results: At the postoperative 6-month visit, no significant difference was observed in the decentered distance between the HA and LA groups (HA: 0.17 ± 0.08 mm, LA: 0.16 ± 0.08 mm, P = 0.189). No significant differences in the correction index (P = 0.481), absolute angle of error (P = 0.104), or index of success (P = 0.147) were observed between the two groups. There was no significant difference in the induction of corneal aberrations between the two groups. Furthermore, there were no significant associations between the decentered distance and the vector components of astigmatic correction or induction of higher-order aberration in the HA group (P ≥ 0.294, P ≥ 0.112) or the LA group (P ≥ 0.323, P ≥ 0.080). Conclusions: SMILE for high keratometric astigmatism could achieve comparable treatment centration and visual quality to that of low keratometric astigmatism.

Comparison of Optical Zone Decentration Following FS-LIKE and SMI-LIKE for Correcting Hyperopia.

PURPOSE: To investigate optical zone decentration following femtosecond laser-assisted lenticule intrastromal keratoplasty (FS-LIKE) or small incision lenticule intrastromal keratoplasty (SMI-LIKE) for correcting hyperopia. METHODS: This study analyzed decentration values obtained from optical coherence tomography (OCT) and tangential topography difference maps of 23 eyes (18 patients) undergoing FS-LIKE (n = 12) or SMI-LIKE (n = 11) via the concentric centration method. Total higher order aberrations (HOAs) and component aberrations were measured preoperatively and 6 months postoperatively. RESULTS: The mean optical zone decentration was 0.27 ± 0.08 and 0.39 ± 0.16 mm for the FS-LIKE and SMI-LIKE groups, respectively (P = .039). A significant difference was noted in lenticule decentration between the two groups (0.18 vs 0.37 mm), whereas no significant difference was observed in stromal bed (pocket) decentration between the two groups (0.10 vs 0.12 mm). Six months after surgery, the spherical equivalent showed a reduction of 6.14 ± 2.44 and 6.10 ± 1.79 diopters (D) for the two groups, respectively (P = .971), whereas the surgically induced astigmatism was 0.68 ± 0.49 and 1.56 ± 0.78 D for the two groups, respectively (P = .004). Furthermore, induction of HOAs in the SMI-LIKE group was significantly larger than that in the FS-LIKE group (P = .013). CONCLUSIONS: FS-LIKE can yield improved treatment centration and less induction of total HOAs. [J Refract Surg. 2022;38(3):184-190.].