Comparison of corneal aberrations and refractive outcomes after small-incision lenticule extraction and femtosecond-assisted laser-assisted in situ keratomileusis

Intensive topical steroid regimen for enhanced very early recovery after small incision lenticule extraction

OBJECTIVE

This study aims to investigate the topical steroid regimen after small incision lenticule extraction (SMILE) for its effect on very early restoration of visual quality.

METHODS

A total of 180 patients (360 eyes) who underwent SMILE were enrolled. These patients were randomly assigned to three groups, with 60 patients in each group. The only difference among these three groups was the administration of 0.1% fluorometholone (FML) eye drops within two hours after SMILE: no FML in group A, 0.1% FML once every hour in group B and 0.1% FML once every half hour in group C. The corrected distance visual acuity (CDVA), objective scattering index (OSI), modulation transfer function (MTF) cut-off, Strehl ratio (SR) and incidence of subjective symptoms were evaluated preoperatively, at 2, 4 and 24 h and one week after SMILE.

RESULTS

The CDVA, MTF cut-off and SR values were significantly higher in group C, when compared to the other two groups, at 2 and 4 h after SMILE (p < 0.05). Furthermore, the OSI and incidence of subjective symptoms were significantly lower in group C, when compared to the other two groups, at 2 and 4 h after SMILE (p < 0.05). However, no significant differences in CDVA, MTF cut-off, SR, OSI and the incidence of subjective symptoms were detected among the three groups at 24 h and one week after SMILE (p > 0.05).

CONCLUSION

The administration of 0.1% FML eye drops every half hour within two hours after SMILE accelerates the restoration of visual and optical quality, and reduces the incidence of subjective symptoms during the very early phase after surgery.

Optical Performance of a Segmented Extended-Depth-of-Focus Intraocular Lens under the Influence of Different Values of Spherical Aberration Generated by Refractive Surgery

BACKGROUND

Corneal refractive surgery induces high-order aberrations, specifically spherical aberration (SA). These aberrations can have implications when patients later develop cataracts and require the implantation of multifocal intraocular lenses (MIOLs). MIOLs with asymmetric designs pose challenges in predicting outcomes, particularly in these cases. The aim of this study was to evaluate how different values of SA, resulting from various types of refractive surgeries, affect the optical performance of the FEMTIS Comfort intraocular lens.

METHODS

The through-focus modulation transfer function (TF-MTF) curve and high-contrast images of tumbling E were used as parameters to assess the optical performance of the MIOL. These parameters were measured using an adaptive optics visual simulator.

RESULTS

Increasingly negative values of SA make the MIOL more bifocal, moderating its extended-depth-of-focus characteristic. Conversely, higher positive SA values cause the TF-MTF curve to shift towards positive vergences, leading to worsened distance vision in the +1.00 to +2.00 D range, but improved vision in the +0.50 D to +1.00 D range.

CONCLUSIONS

Assessing SA in patients prior to implanting MIOLs with asymmetric designs is necessary for predicting outcomes and making informed decisions based on the visual requirements of patients.

Small Incision Lenticule Extraction (SMILE) Versus Laser Assisted Stromal In Situ Keratomileusis (LASIK) for Astigmatism Corrections: A Systematic Review and Meta-analysis

PURPOSE

To compare small incision lenticule extraction (SMILE) and laser assisted stromal in situ keratomileusis (LASIK) for astigmatism correction.

DESIGN

Systematic review and meta-analysis METHODS: We reviewed published studies comparing outcomes after LASIK and SMILE for astigmatism correction by querying PubMed, EMBASE, Cochrane, and Web of Science, with a cut-off date of September 3, 2022. We also compared the changes in visual acuity, refraction, and high-order aberrations between the surgeries. Astigmatism correction outcomes in the low-to-moderate group (less than or equal to -2.00 D) and high group (greater than -2.00 D) were evaluated using vector analysis. The Cochrane risk of bias tool in RevMan software was used for randomized studies (RCT), and Risk Of Bias In Nonrandomized Studies - of Interventions (ROBINS-I) was used for the nonrandomized studies (NRSs).

RESULTS

There were 17 studies (5 randomized studies and 12 cohort studies), including 1,985 eyes. A statistically significant difference was found in the correction index (mean difference [MD] = -0.02, 95% confidence interval [CI] = -0.04 to -0.01, P =0.01), although there was no significant difference in the index of success (MD = 0.01, 95% CI = -0.03 to 0.05, P =0.51), different vector (MD = 0.07, 95% CI = 0.00 to 0.13, P =0.04), and angle of error (MD = 0.56, 95% CI = -0.34 to 1.45, P =0.22) between SMILE and LASIK. However, for low-to-moderate astigmatism correction, SMILE exhibited a smaller correction index (MD = -0.08, 95% CI= -0.13 to -0.02, P =0.008) and a larger difference vector (MD = 0.18, 95% CI = 0.09 to 0.27, P <0.0001) than LASIK. There was no significant difference between the different procedures in visual acuity and refraction (spherical equivalent: MD = -0.04, 95% CI = -0.08 to 0.01, P =0.15) or high-order aberration (MD = -0.01, 95% CI = -0.07 to 0.04, P =0.67), except spherical aberration (MD = -0.12, 95% CI = -0.23 to -0.01, P =0.04). The risk of bias was moderate in most studies because of poor reporting of several bias domains for RCTs, and because of confounding and selective outcome reporting for NRSs.

CONCLUSIONS

When used to treat severe astigmatism, both SMILE and LASIK provide effective and predictable results and generally have equivalent outcomes. However, evidence reveals a tendency toward undercorrection in the SMILE groups for astigmatism correction. In addition, LASIK has a greater probability of causing postoperative spherical aberration.