Influence of Refractive Status on the Higher-Order Aberration Pattern After Small Incision Lenticule Extraction Surgery

Association of myopia and astigmatism with postoperative ocular high order aberration after small incision lenticule extraction

OBJECTIVE

To investigate the correlation between higher-order aberrations (HOA) after small incision lenticule extraction (SMILE) and the severity of myopia and astigmatism, along with the relevant factors. These findings will provide valuable insights for decreasing the occurrence of HOA after SMILE and enhancing visual quality.

METHODS

A total of 75 patients (150 eyes) with myopia and astigmatism who underwent SMILE were categorized into four groups based on the severity of myopia and astigmatism: Myopia Group 1 (Group M1, spherical diopter ranged from -1.00 D to -4.00 D), Myopia Group 2 (Group M2, spherical diopter ranged from -4.10 D to -10.00 D), Astigmatism Group 1 (Group A1, cylindrical diopter ranged from 0 D to -1.00 D), and Astigmatism Group 2 (Group A2, cylindrical diopter ranged from -1.10 D to -3.00 D). A comprehensive assessment was performed to examine the association between HOA and various relevant factors, including a detailed analysis of the subgroups.

RESULTS

Group M1 had significantly lower levels of total eye coma aberration (CA), corneal total HOA (tHOA), internal tHOA, and vertical CA ( Z 3 - 1 ) after SMILE than Group M2 (P < 0.05). Similarly, Group A1 had significantly lower levels of total eye tHOA, CA, trefoil aberration (TA), corneal tHOA, TA, and vertical TA ( Z 3 - 3 ) after SMILE than Group A2 (P < 0.05). Pearson correlation analysis indicated a statistically significant positive relationship between the severity of myopia/astigmatism and most HOA (P < 0.05). Subgroup evaluations demonstrated a notable increase in postoperative HOA associated with myopia and astigmatism in Groups M2 and A2 compared with the control group. Lenticule thickness, postoperative central corneal thickness (CCT), postoperative uncorrected distance visual acuity (UDVA), and postoperative corneal Km and Cyl were strongly correlated with most HOA. Age, eyes, and postoperative intraocular pressure (IOP) were only associated with specific HOA.

CONCLUSION

HOA positively correlated with the severity of myopia and astigmatism after SMILE. However, this relationship was not linear. HOA after SMILE was influenced by various factors, and additional specialized investigations are required to establish its clinical importance.

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

PURPOSES

To retrospectively compare the short-term refractive outcomes and corneal aberrations after small-incision lenticule extraction (SMILE) and femtosecond-assisted laser-assisted in situ keratomileusis (FS-LASIK) combined with smart pulse technology (SPT) in patients with compound myopic astigmatism.

METHODS

A total of 91 eyes (91 patients) were included, 43eyes in FS-LASIK group and 48 eyes in the SMILE group. Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), refractive results and corneal topography were evaluated 1 and 3 months postoperatively. Corneal aberrations of anterior corneal surface were calculated from the topography data over 6 mm-diameter.

RESULTS

There was no significant difference in UCVA, BCVA, and refractive results between the two groups. There were no statistical difference in TIA (target induced astigmatism), SIA (surgery induced astigmatism), DV (difference vector), ME (magnitude of error), AE (angle of error), AE (absolute value) and CI (correction index) between both groups at 1 and 3 months. Coma and spherical aberration improved in all the patients in both groups at 1 and 3 months postoperatively. The amount of induced spherical aberrations was higher in FS-LASIK group compared to SMILE group.

CONCLUSIONS

Both FS-LASIK and SMILE achieved similar refractive outcomes in patients with myopia and compound myopic astigmatism. FS-LASIK combined with SPT resulted in higher spherical aberration than SMILE in early postoperative period.

Relation of Corneal Astigmatism with Various Corneal Image Quality Parameters in a Large Cohort of Naïve Corneas

Purpose

To investigate the relationship between corneal astigmatism and corneal image quality parameters (i.e., root mean square [RMS] of some major corneal higher order aberrations [HOAs] “namely RMS of coma aberrations, RMS of trefoil aberrations, and RMS of spherical aberration [RMS-SA]” and Strehl ratio [SR] of point spread function [PSF]) by using the Sirius topographer (CSO Italia, Florence, Italy).

Patients and Methods

This cross-sectional study used the Sirius topographer to evaluate the naïve corneas of right eyes (n = 1,356). The study included three groups which were based on the mean anterior corneal astigmatism value (group 1, <1 D; group 2, 1–2 D; and group 3, >2 D).

Results

The corneal astigmatism showed statistically significant (yet narrow clinical) differences among the groups regarding all the examined parameters (P<0.001), except for the RMS-SA (which was statistically insignificant among the three groups). Correlation coefficients were weak between the corneal astigmatism and HOAs (correlation coefficient “r” not reaching 0.2 with any of the evaluated HOAs).

Conclusion

Significant differences existed among the astigmatic groups regarding corneal HOAs, but the mean values were very close. The deduced relations between corneal astigmatism and corneal image quality parameters had limited clinical relevance. Thus, the corneal astigmatism should be evaluated separately from corneal image quality parameters, either when deciding between refractive correction modalities (customized versus optimized ablation techniques) or when evaluating corneal image quality of a naïve cornea.

15-Month Visual Outcomes and Corneal Power Changes of SMILE in Treating High Myopia With Maximum Myopic Meridian Exceeding 10.00 D

PURPOSE

To evaluate the long-term visual and refractive outcomes, optical quality, and stability of the cornea and axial length after small incision lenticule extraction (SMILE) for the correction of high myopia with a maximum myopic meridian exceeding 10.00 diopters (D).

METHODS

Via a prospective cohort study, 53 eyes (53 patients) with a maximum myopic meridian exceeding 10.00 D were corrected with a VisuMax femtosecond laser (version 3.0; Carl Zeiss Meditec AG, Jena, Germany) at the Zhongshan Ophthalmic Center of Sun Yat-sen University. Refractive outcomes, aberrations, axial length, and corneal curvature were evaluated preoperatively and at 1, 3, and 15 months postoperatively.

RESULTS

At 15 months postoperatively, the efficacy and safety indexes were 0.91 ± 0.25 and 1.15 ± 0.18, respectively. A total of 72% of eyes were within ±0.50 D and 89% were within ±1.00 D of the attempted spherical equivalent, respectively. From 1 to 15 months postoperatively, the significant regression was -0.24 ± 0.28 D (P < .001) on manifest refraction and -0.43 ± 0.54 D (P < .001) on anterior corneal curvature. In addition, a significant increase of 0.20 µm (P = .016) was observed in the spherical aberration. No significant change was observed in posterior corneal curvature (P > .999), including mean keratometry or astigmatism, or in the ocular axis length from 1 to 15 months postoperatively (26.82 ± 0.93 and 26.82 ± 0.95 mm, respectively, P > .99).

CONCLUSIONS

SMILE had long-term safety, efficacy, and predictability when treating high myopia with a maximum myopic meridian exceeding 10.00 D. Both a manifest refraction regression of -0.24 D and a significant spherical aberration increase of 0.20 µm were observed between 1 and 15 months postoperatively, due to the increased anterior corneal curvature. [J Refract Surg. 2019;35(1):31-39.].

Corneal higher-order aberrations of the anterior surface, posterior surface, and total cornea after small incision lenticule extraction (SMILE): high myopia versus mild to moderate myopia

Background

To investigate corneal higher-order aberrations (HOAs) of the anterior surface, posterior surface, and total cornea after small incision lenticule extraction (SMILE) in high myopic and mild to moderate myopic patients.

Methods

This retrospective study included 197 eyes (101 patients) undergoing SMILE surgery. According to the preoperative spherical equivalent (SE), treated eyes were divided into two groups: a high myopic group (more than − 6.0 D, Group H) and a mild to moderate myopic group (less than − 6.0 D, Group M). Corneal HOAs of the anterior surface, posterior surface, and total cornea were measured using a Scheimpflug camera preoperatively and 3 months postoperatively. Pearson’s correlation analysis was conducted to determine relationships between corneal aberrations and the SE.

Results

There were no significant differences in third-order to eight-order aberrations (RMS HOAs) of the anterior surface, posterior surface, and total corneal between the two groups before SMILE surgery. However, after SMILE, anterior and total corneal HOAs, especially vertical coma and spherical aberrations, significantly increased in both groups (p < 0.0167), whereas posterior corneal HOAs remained relatively stable (p > 0.0167). The induction of HOAs was significantly greater in Group H than Group M postoperatively (p < 0.0167). Changes in anterior surface and total corneal HOAs, especially vertical coma and spherical aberrations, were related to the SE (p < 0.05).

Conclusions

Anterior and total corneal HOAs, particularly vertical coma and spherical aberrations, significantly increased after SMILE in both groups, whereas posterior corneal HOAs remained stable. Aberration changes were related to SE.

Trial registration

Retrospectively registered. ChiCTR-ORC-17011040. Registered 1 April 2017. Name of registry: The observation of clinical results after corneal refractive surgery. Data of enrolment of the first participant to the trial: 15 December 2016.

Single-step Transepithelial photorefractive keratectomy in the treatment of mild, moderate, and high myopia: six month results

Background

To evaluate the safety, efficacy, and the refractive outcomes of single-step transepithelial photorefractive keratectomy (TransPRK) for the correction of mild, moderate, and high myopia.

Methods

This study consecutively recruited 32 high myopic eyes, 32 mild myopic and 32 moderate myopic eyes. Eyes with myopia that had undergone TransPRK treatment. Pre- and post-operative visual and refractive data, corneal Higher Order Aberration (HOA) as well as safety and efficacy indices were analyzed at 6 months postoperatively.

Results

Six months after TransPRK, the manifest refraction spherical equivalent (SE) was not significantly between high myopia group and moderate myopia group (p = 0.636). No eyes lost ≥2 lines of corrected distant visual acuity (CDVA) in high myopic eyes. The uncorrected distance visual acuity (UDVA) was significantly higher in low and moderate myopia groups than the high myopia group (P < 0.001; P = 0.002). The CDVA was not significantly different between moderate and high myopia groups (P = 0.057). There was no significant difference in mean safety index between high myopia group (1.01 ± 0.14) and mild myopia group (1.08 ± 0.15) (P > 0.05). The mean safety index was significantly higher in the moderate myopia group (1.16 ± 0.23) than in the high myopia group (1.01 ± 0.14) (P = 0.002). The efficacy index was significantly higher in the moderate myopia group (1.05 ± 0.20) than in the high myopia group (0.89 ± 0.17) (P = 0.02), and there was no significant difference between the high myopia group (0.89 ± 0.17) and the low myopia group (0.96 ± 0.16) (P = 0.14).

Conclusions

The mean safety index was over 1.0 in the three groups. TransPRK showed acceptable safety and efficacy in the moderate myopic eyes, as well as mild and high myopic eyes. High myopic eyes got very similar refractive results with moderate myopic eyes six months postoperatively. The safety and efficacy indexes were not significantly different between the high myopia group and the low myopia group.

Peripheral refraction and image blur in four meridians in emmetropes and myopes

INTRODUCTION

The peripheral refractive error of the human eye has been hypothesized to be a major stimulus for the development of its central refractive error.

AIM

The purpose of this study was to investigate the changes in the peripheral refractive error across horizontal, vertical and two diagonal meridians in emmetropic and low, moderate and high myopic adults.

SUBJECTS AND METHODS

Thirty-four adult subjects were recruited and aberration was measured using a modified commercial aberrometer. We then computed the refractive error in power vector notation from second-order Zernike terms. Statistical analysis was performed to evaluate the statistical differences in refractive error profiles between the subject groups and across all measured visual field meridians.

RESULTS

Small amounts of relative myopic shift were observed in emmetropic and low myopic subjects. However, moderate and high myopic subjects exhibited a relative hyperopic shift in all four meridians. Astigmatism J0 and J45 had quadratic or linear changes dependent on the visual field meridians. Peripheral Sphero-Cylindrical Retinal Image Blur increased in emmetropic eyes in most of the measured visual fields.

CONCLUSION

The findings indicate an overall emmetropic or slightly relative myopic periphery (spherical or oblate retinal shape) formed in emmetropes and low myopes, while moderate and high myopes form relative hyperopic periphery (prolate, or less oblate, retinal shape). In general, human emmetropic eyes demonstrate higher amount of peripheral retinal image blur.