Refractive Regression and Changes in Central Corneal Thickness Three Years after Laser-Assisted Subepithelial Keratectomy for High Myopia in Eyes with Thin Corneas: A Retrospective Study

Comparison of central corneal thickness treated with small incision lenticule extraction, femtosecond laser-assisted in situ keratomileusis, or laser-assisted subepithelial keratomileusis for myopia

To compare the central corneal thickness (CCT) treated with small incision lenticule extraction (SMILE), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), or laser-assisted subepithelial keratomileusis (LASEK) for myopia correction. This was a retrospective case series study. Patients who had completed 1-year follow-up after receiving SMILE, FS-LASIK, or LASEK at our hospital from January 2019 to July 2021 were included. Pentacam pachymetry was performed to measure the CCT. The predicted CCT reduction was obtained through laser platform. The measured CCT reduction was defined as the difference between the preoperative and postoperative CCT using Pentacam pachymetry. There were 100 eyes treated by SMILE, 100 eyes by FS-LASIK, and 100 eyes by LASEK. There was a significant difference in predicted CCT reduction among the three surgeries (P < 0.001), but no significant difference in measured CCT reduction postoperatively (PGroup = 0.373). At 1 year postoperatively, the CCT reduction was overestimated by 17.85 ± 5.36 µm in the SMILE group, underestimated by 4.31 ± 7.08 µm in the FS-LASIK group, and underestimated by 7.60 ± 8.28 µm in the LASEK group (PGroup < 0.001, PTime < 0.001). In the FS-LASIK group, the difference between predicted and measured CCT reduction was not related to the predicted CCT reduction (P = 0.095). The laser platform may overestimate the CCT reduction for SMILE and underestimate it for FS-LASIK and LASEK. FS-LASIK has a much higher level of accuracy in CCT reduction, which is not influenced by refractive correction.

Postoperative corneal biomechanics and influencing factors during femtosecond-assisted laser in situ keratomileusis (FS-LASIK) and laser-assisted subepithelial keratomileusis (LASEK) for high myopia

The purpose of this study is to compare the postoperative corneal biomechanics and assess the influence factors after femtosecond-assisted laser in situ keratomileusis (FS-LASIK) and laser-assisted subepithelial keratomileusis (LASEK) for high myopia. In this retrospective study, patients who completed 1-year follow-up were included. The corneal biomechanical parameters, including deformation amplitude ratio 2.0 mm (DA ratio 2.0 mm), integrated inverse radius (IntInv Rad), stiffness parameter at first applanation (SP-A1), and Ambrosio relational thickness through the horizontal meridian (ARTh), were measured with Corvis STII. We also investigated the relationship between these biomechanics and preoperative or intraoperative variables. Thirty eyes had FS-LASIK and 30 eyes had LASEK. The changes in DA ratio 2.0 mm, IntInv Rad, and SP-A1 after surgery were significantly smaller in the LASEK group than in the FS-LASIK group, while the change in the ARTh was not significantly different between groups. No significant differences were detected in the mean values of postoperative DA ratio 2.0 mm, IntInv Rad, and SP-A1 between LASEK and FS-LASIK, while significant difference was detected in the mean value of postoperative ARTh. There was a significant correlation between the resident stromal bed thickness and the postoperative DA ratio 2.0 mm, IntInv Rad, or SP-A1. The postoperative ARTh has shown significant correlation with postoperative central corneal thickness and the amount of myopic correction. The effect of LASEK on corneal biomechanics was smaller than FS-LASIK when the same central corneal thickness was consumed. LASEK may be performed with a lower risk of postoperative corneal ectasia than FS-LASIK.

A pilot study: LASEK with the Triple-A profile of a MEL 90 for mild and moderate myopia

Background

To investigate the visual and refractive outcomes in patients with mild to moderate myopia after laser-assisted subepithelial keratectomy (LASEK) using the 500 Hz pulse rate of the Triple-A profile.

Methods

Thirty-six eyes of 20 patients (mean age, 27.5 ± 4.6 years) were included in this prospective, consecutive study. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), corneal topography, and corneal aberrations were measured preoperatively and 1 day, 1 week, 1, 3 and 6 months post-operation.

Results

At 1 week after surgery, UDVA was better than or equal to 20/25 in all eyes. At postoperative 6 months, the efficacy and safety index was 1.05 ± 0.13 and 1.12 ± 0.15, respectively; all eyes had a UDVA of 20/20 or better, and no eyes showed a loss in CDVA; 100% of the eyes were within ±1.00 D of the attempted spherical equivalent (SE) correction.

Conclusion

The postoperative results indicate that using the Triple-A ablation profile of the MEL 90 excimer laser with a 500 Hz pulse rate is a safe, efficient, and predictable method to correct mild to moderate myopia.