Wavefront ablation profiles in refractive surgery: description, results, and limitations

Clinical outcomes of SMILE and WFG-LASIK used to treat myopia and astigmatism: A systematic review and meta-analysis

PURPOSE

To evaluate the safety, efficacy and postoperative visual quality of small incision lenticule extraction (SMILE) and Wavefront-Guided Laser in situ keratomileusis (WFG-LASIK) and to analyze their efficacy in correcting astigmatism.

METHODS

A systematic literature search was performed using Cochrane Collaboration methodology. Databases searched included PubMed, Embase, the Cochrane Library and Web of Science. RevMan software version 5.3.0 was used for meta-analysis.

RESULTS

A total of 976 eyes were included in 8 studies, of which 539 eyes underwent SMILE and 437 eyes underwent WFG-LASIK. There were no statistically significant differences in the proportion of eyes achieving uncorrected distance visual acuity of 20/20 or better (P=0.18), the proportion of eyes within±0.50 diopter of target refraction postoperatively (P=0.10), or the postoperative magnitude of cylinder (P=0.10). Regarding the Alpins vector analysis of astigmatism, there was no statistically significant difference in the surgical magnitude of error (P=0.09) between the two groups. WFG-LASIK has a lower surgical angle of error (P= 0.002) and higher surgical correction index of cylinder (P=0.03) than SMILE. In terms of aberrations, higher order aberrations (P=0.46), spherical aberrations (P=0.22) and trefoil (P=0.56) were not statistically different, while WFG-LASIK induced less coma than SMILE surgery (P=0.02).

CONCLUSION

Both SMILE and WFG-LASIK are safe and effective ways to correct myopia and astigmatism. Compared with SMILE, WFG-LASIK has a lower surgical angle of error, higher surgical correction index of cylinder and induces less coma.

Ray-Tracing Customization in Myopic and Myopic Astigmatism LASIK Treatments for Low and High Order Aberrations Treatment: 2-Year Visual Function and Psychometric Value Outcomes of a Consecutive Case Series

Purpose

The safety and long-term efficacy of automated ray-tracing customized myopic and myopic astigmatic femtosecond laser-assisted LASIK.

Methods

This consecutive case series retrospective analysis, of 20 subjects (40 eyes) treated with automated raytracing named Wavelight Plus, to include low and high order aberrations based on a three-dimensional custom virtual eye for each case-calculated from interferometry data-obtained from a single diagnostic device that also provides Hartman-Shack Wavefront and Scheimpflug tomography data. We evaluated before and after the customized LASIK procedure: visual acuity, refractive error, high order aberrations, contrast sensitivity, and psychometric post-operative visual function data.

Results

At 24 months, the comparison of the pre-operative to the post-operative refractive and visual function value changes in average were: subjective manifest refraction from -4.38 ± 2.54 diopters (D) (range -9.75 to -1.25 D) to +0.11 ± 0.19 D; subjective manifest refractive astigmatism from -0.76 ± 0.91 D (range -2.75 to 0 D) to -0.13 ± 0.16 D, corneal astigmatism from -1.16 ± 0.64 D (range -0.2 to -2.8) to -0.47 ± 0.11 D. 65% of the eyes studied demonstrated an increase of at least one line of vision, while from the same group 38% demonstrated 2 lines of increase. High order aberrations, contrast sensitivity as well as the subjective psychometric input based on the VFQ-25 questionnaire demonstrated actual improvement.

Conclusion

This longer-term follow-up, single-arm retrospective consecutive case series documents LASIK treatment customization that appears to be safe and effective in the correction of myopia and myopic astigmatism. Markedly improved objective and subjective visual function post-operatively, underlying the potential importance of simultaneously attempting to correct high order aberrations and improving the spatial alignment of total, measured human eye optics.

Influence of the Reference Center on the Calculation of Corneal Higher Order Aberrations

PURPOSE

To evaluate the differences in corneal wavefront measurements in myopic and hyperopic eyes when calculated using three different reference centers and explore possible influencing factors for such differences.

METHODS

Corneal wavefront measurements were performed in myopic and hyperopic eyes using a GALILEI Placido Dual Scheimpflug Analyzer (Ziemer Ophthalmic Systems AG). Corneal higher order aberrations (HOAs), including total, vertical, and horizontal coma-like aberrations, spherical aberrations, and total corneal HOAs through a 6-mm pupil size, were calculated over three different reference center positions: pupil center, corneal vertex, and limbus to limbus. Values were then compared between the myopic and hyper-opic eyes, and correlations with kappa distance and spherical equivalent were tested.

RESULTS

A significant decrease in the level of total corneal HOAs (-0.04 ± 0.05 and -0.12 ± 0.09), total corneal coma (-0.07 ± 0.09 and -0.18 ± 0.12), and horizontal coma (-0.07 ± 0.11 and -0.22 ± 0.11) in myopic and hyperopic eyes, respectively, was found when recalculating from pupil center to corneal vertex centration, whereas a significant increase in the same aberrations was observed from pupil center or corneal vertex to limbus to limbus. Significant correlations were found between the kappa distance and changes in total corneal HOAs, total corneal coma, and horizontal coma from the pupil center to the corneal vertex in both groups.

CONCLUSIONS

Corneal vertex centration generated the lowest level of corneal wavefront error in both groups. The differences in corneal aberrations between the reference centers for calculation were highly correlated with the kappa distance in hyperopic eyes. [J Refract Surg. 2023;39(5):340-346.].

A Comparison of Three Cylindrical Treatment Strategies for Topography-Guided LASIK: Manifest, Topographic, and ZZ VR Cylinders

Purpose

This study was designed to compare the clinical outcomes of three cylindrical treatment strategies using manifest, topographic, and Zhang & Zheng vector-compensated refraction (ZZ VR) cylinders, for topography-guided laser-assisted in situ keratomileusis (LASIK) and to identify the laser programming strategy that optimizes refractive astigmatism outcomes and visual acuity.

Methods

Consecutive patients referred for therapeutic refractive surgery between March and September 2018 at a single center were prospectively analyzed. Using double-masked simple randomization, patients were randomly assigned to undergo treatment based on manifest cylinder, topographic cylinder, and ZZ VR cylinder strategies. Uncorrected distance visual acuity and astigmatic refraction were analyzed preoperatively and 6 months postoperatively.

Results

A total of 138 eyes from 71 patients met the inclusion criteria. The manifest group consisted of 46 eyes in 24 patients, the topographic group consisted of 43 eyes in 22 patients, and the ZZ VR group consisted of 49 eyes in 25 patients. The absolute residual cylindrical refractions at 6 months postoperatively in these three groups were 0.69 ± 0.32 D, 0.58 ± 0.31 D, and 0.42 ± 0.19 D, respectively (P < 0.001; adjusted P < 0.01 for manifest vs ZZ VR, adjusted P = 0.08 for topographic vs ZZ VR). The percentages of postoperative absolute residual cylindrical power within 0.50 D in the manifest, topographic, and ZZ VR groups were 30.4%, 55.8%, and 59.2%, respectively (P = 0.01; adjusted P = 0.06 for manifest vs topographic, adjusted P = 0.02 for manifest vs ZZ VR).

Conclusion

The ZZ VR strategy may achieve better outcomes, as determined by cylindrical correction and visual activity, during topography-guided LASIK.

Clinical Trial Registration Number

ChiCTR1900025779.

Advanced Optical Wavefront Technologies to Improve Patient Quality of Vision and Meet Clinical Requests

Adaptive optics (AO) is employed for the continuous measurement and correction of ocular aberrations. Human eye refractive errors (lower-order aberrations such as myopia and astigmatism) are corrected with contact lenses and excimer laser surgery. Under twilight vision conditions, when the pupil of the human eye dilates to 5-7 mm in diameter, higher-order aberrations affect the visual acuity. The combined use of wavefront (WF) technology and AO systems allows the pre-operative evaluation of refractive surgical procedures to compensate for the higher-order optical aberrations of the human eye, guiding the surgeon in choosing the procedure parameters. Here, we report a brief history of AO, starting from the description of the Shack-Hartmann method, which allowed the first in vivo measurement of the eye's wave aberration, the wavefront sensing technologies (WSTs), and their principles. Then, the limitations of the ocular wavefront ascribed to the IOL polymeric materials and design, as well as future perspectives on improving patient vision quality and meeting clinical requests, are described.

Repeatability and reproducibility of corneal higher-order aberrations measurements after small incision lenticule extraction using the Scheimpflug-Placido topographer

Background

To evaluate the precision of corneal higher-order aberrations measurements after small incision lenticule extraction (SMILE) using the Sirius Scheimpflug-Placido topographer (CSO, Italy).

Methods

Seventy-five eyes from 75 postoperative subjects were included in this prospective study. Three consecutive corneal aberrometric measurements were obtained with the Scheimpflug-Placido topographer by two experienced operators to assess intra- and inter-observer reproducibility. The within-subject standard deviation (S_w), test-retest repeatability (TRT) and the intraclass correlation coefficient (ICC) were calculated.

Results

For intraobserver repeatability of anterior and total corneal aberrations, all ICCs were more than 0.922, except for trefoil (0.722 to 0.768). The ICCs of total root mean square (RMS), coma Z (3, ± 1), and spherical aberration Z (4, 0) were over 0.810 while higher-order RMS, trefoil Z (3, ± 3), and astigmatism II Z (4, ± 2) were below 0.634 for posterior corneal surface aberrations. All S_w values for all types of aberrations were equal to or below 0.07 μm. Regarding interobserver reproducibility, all TRT values were no more than 0.12 μm, 0.05 μm, and 0.11 μm for anterior, posterior, and total corneal aberrations, respectively. The ICC values ranged from 0.875 to 0.989, from 0.686 to 0.976 and over 0.834 for anterior, posterior, and total corneal aberrations, respectively.

Conclusions

The repeatability of measurements of anterior and total corneal aberrations with the Sirius system in corneas after SMILE surgery was high, except for trefoil. There was some variability in posterior corneal aberrometric measurements. High reproducibility of corneal aberrometric measurements was observed between measurements of both examiners, except for trefoil, with poor to moderate reproducibility.

Q-value customized versus wavefront-optimized ablation in femtosecond laser-assisted LASIK for myopia and myopic astigmatism: a prospective contralateral comparative study

Background

Corneal refractive surgery for myopia results in an oblate shift with increased postoperative aberrations inversely affecting the quality of vision. Aspheric ablation profiles have been introduced to minimize such a problem. The aim of this study was to compare changes in corneal asphericity, central and mid-peripheral pachymetry between the Q-value customized and the wavefront-optimized (WFO) ablation profiles.

Methods

A prospective, comparative non-randomized fellow eye study was conducted. Eighty eyes of 40 eligible patients underwent femtosecond laser-assisted laser in situ keratomileusis for myopia and myopic astigmatism. In each patient, the more myopic eye was included in the custom-Q ablation experimental group and the other less myopic eye was included in the WFO control group. For the custom-Q group, the target asphericity was set to the preoperative Q-value. Corneal asphericity, central and mid-peripheral pachymetric changes and the root mean square of corneal higher-order aberrations (RMSh) were assessed 6 months following surgery. Visual and refractive outcomes were also evaluated in both platforms 6 months postoperatively.

Results

The mean preoperative refractive spherical equivalent was significantly more myopic in the custom-Q group than in the WFO group (P = 0.001). The mean Q-value changed from − 0.2 ± 0.1 to 0.6 ± 0.7 and from − 0.2 ± 0.1 to 0.4 ± 0.5 in the custom-Q and WFO groups, respectively. The oblate shift in corneal asphericity was not significantly different between both treatment groups (P = 0.094). The mean ablation depth at the pupillary center was significantly greater in the custom-Q group (P = 0.011), while there was no significant difference at the mid-peripheral pachymetry (P = 0.256). The RMSh significantly increased in both treatment profiles (P < 0.001) with no significant difference between the two groups (P = 0.06). The uncorrected distance visual acuity (UDVA) and the manifest refraction spherical equivalents (MRSE) significantly improved in both treatment groups (P < 0.001).

Conclusions

The custom-Q treatment profile with target asphericity set at the preoperative Q-value achieved comparable outcomes vs. the WFO profile in terms of postoperative corneal asphericity and mid-peripheral pachymetry despite the greater amount of ablation, the smaller optical zone, and the resulting increase in postoperative corneal flattening in the custom-Q group.

Trial registration (Clinicaltrials.gov): NCT04738903, 4 February 2021- Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04738903

A comparison between wavefront-optimized and wavefront-guided photorefractive keratectomy in patients with moderate-to-high astigmatism: A randomized clinical trial

Purpose:

Methods:

Results:

Conclusion:

Topography-Guided Femto-LASIK in Virgin Eyes: Treating Manifest versus Measured Astigmatism

Purpose

To assess the stability, safety, predictability, and efficacy of topography-guided myopic Femto-LASIK with two different treatment protocols.

Setting

Ebsar Eye center, Benha, Qalyopia, Egypt.

Design

Single-center, retrospective, COHORT control study.

Methods

A total of 330 eyes enrolled in the study in group A and 322 eyes enrolled in group B underwent uncomplicated primary bilateral topography-guided Femto-LASIK. Group A was treated with the subjective clinical refraction; however, group B was treated with the modified refraction according to ALCON protocol.

Results

The mean preoperative refractive spherical equivalent (MRSE) was −4.85±1.90D and −5.0±1.93D in group A and B, respectively (P = 0.86), and a cylinder of −0.95±0.80 D and −0.92±0.81D, respectively. At the 12 months’ postoperatively, the residual manifest SE within ± 0.5D was achieved by 82.86% of eyes in group A compared to 83.93% in group B. Of eyes, 92.06% had ≤0.5 astigmatism dioptre, while 100% of eyes had ≤1.0 astigmatism dioptre in group A (315 eyes); however, 91.80% of eyes had ≤0.5 astigmatism dioptre, while 100% of eyes had ≤1.0 astigmatism dioptre in group B.

Conclusion

Topographic modification of the magnitude and axis of astigmatism treated using ALCON protocol when different from the clinical refraction may offer good refractive outcomes when we apply the Alcon precalculation considerations.

Wavefront excimer laser refractive surgery for adults with refractive errors

BACKGROUND

Refractive errors (conditions in which the eye fails to focus objects accurately on the retina due to defects in the refractive system), are the most common cause of visual impairment. Myopia, hyperopia, and astigmatism are low-order aberrations, usually corrected with spectacles, contact lenses, or conventional refractive surgery. Higher-order aberrations (HOAs) can be quantified with wavefront aberration instruments and corrected using wavefront-guided or wavefront-optimized laser surgery. Wavefront-guided ablations are based on preoperative measurements of HOAs; wavefront-optimized ablations are designed to minimize induction of new HOAs while preserving naturally occurring aberrations. Two wavefront procedures are expected to produce better visual acuity than conventional procedures.

OBJECTIVES

The primary objective was to compare effectiveness and safety of wavefront procedures, laser-assisted in-situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) or laser epithelial keratomileusis (LASEK) versus corresponding conventional procedures, for correcting refractive errors in adults for postoperative uncorrected visual acuity, residual refractive errors, and residual HOAs. The secondary objective was to compare two wavefront procedures.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, which contains the Cochrane Eyes and Vision Trials Register; 2019, Issue 8); Ovid MEDLINE; Ovid Embase; Latin American and Caribbean Health Sciences (LILACS); the ISRCTN registry; ClinicalTrials.gov and the WHO ICTRP. The date of the search was 6 August 2019. We imposed no restrictions by language or year of publication. We used the Science Citation Index (September 2013) and searched the reference lists of included trials to identify additional relevant trials.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) comparing either wavefront modified with conventional refractive surgery or wavefront-optimized with wavefront-guided refractive surgery in participants aged ⪰ 18 years with refractive errors.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodology.

MAIN RESULTS

We identified 33 RCTs conducted in Asia, Europe and United States, totaling 1499 participants (2797 eyes). Participants had refractive errors ranging from high myopia to low hyperopia. Studies reported at least one of the following review-specific outcomes based on proportions of eyes: with uncorrected visual acuity (UCVA) of 20/20 or better, without loss of one or more lines of best spectacle-corrected visual acuity (BSCVA), within ± 0.50 diopters (D) of target refraction, with HOAs and adverse events. Study characteristics and risk of bias Participants were mostly women, mean age 29 and 53 years, and without previous refractive surgery, ocular pathology or systemic comorbidity. We could not judge risks of bias for most domains of most studies. Most studies in which both eyes of a participant were analyzed failed to account for correlations between two eyes in the analysis and reporting of outcomes. Findings For the primary comparison between wavefront (PRK or LASIK or LASEK) and corresponding conventional procedures, 12-month outcome data were available from only one study of PRK with 70 participants. No evidence of more favorable outcomes of wavefront PRK on proportion of eyes: with UCVA of 20/20 or better (risk ratio [RR] 1.03, 95% confidence interval (CI) 0.86 to 1.24); without loss of one or more lines of BSCVA (RR 0.94, 95% CI 0.81 to 1.09); within ± 0.5 D of target refraction (RR 1.03, 95% CI 0.86 to 1.24); and mean spherical equivalent (mean difference [MD] 0.04, 95% CI -0.11 to 0.18). The evidence for each effect estimate was of low certainty. No study reported HOAs at 12 months. At six months, the findings of two to eight studies showed that overall effect estimates and estimates by subgroup of PRK or LASIK or LASEK were consistent with those for PRK at 12 month, and suggest no difference in all outcomes. The certainty of evidence for each outcome was low. For the comparison between wavefront-optimized and wavefront-guided procedures at 12 months, the overall effect estimates for proportion of eyes: with UCVA of 20/20 or better (RR 1.00, 95% CI 0.99 to 1.02; 5 studies, 618 participants); without loss of one or more lines of BSCVA (RR 0.99, 95% CI 0.96 to 1.02; I2 = 0%; 5 studies, 622 participants); within ± 0.5 diopters of target refraction (RR 1.02, 95% CI 0.95 to 1.09; I2 = 33%; 4 studies, 480 participants) and mean HOAs (MD 0.03, 95% CI -0.01 to 0.07; I2 = 41%; 5 studies, 622 participants) showed no evidence of a difference between the two groups. Owing to substantial heterogeneity, we did not calculate an overall effect estimate for mean spherical equivalent at 12 months, but point estimates consistently suggested no difference between wavefront-optimized PRK versus wavefront-guided PRK. However, wavefront-optimized LASIK compared with wavefront-guided LASIK may improve mean spherical equivalent (MD -0.14 D, 95% CI -0.19 to -0.09; 4 studies, 472 participants). All effect estimates were of low certainty of evidence. At six months, the results were consistent with those at 12 months based on two to six studies. The findings suggest no difference between two wavefront procedures for any of the outcomes assessed, except for the subgroup of wavefront-optimized LASIK which showed probable improvement in mean spherical equivalent (MD -0.12 D, 95% CI -0.19 to -0.05; I2 = 0%; 3 studies, 280 participants; low certainty of evidence) relative to wavefront-guided LASIK. We found a single study comparing wavefront-guided LASIK versus wavefront-guided PRK at six and 12 months. At both time points, effect estimates consistently supported no difference between two procedures. The certain of evidence was very low for all estimates. Adverse events Significant visual loss or optical side effects that were reported were similar between groups.

AUTHORS' CONCLUSIONS

This review suggests that at 12 months and six months postoperatively, there was no important difference between wavefront versus conventional refractive surgery or between wavefront-optimized versus wavefront-guided surgery in the clinical outcomes analyzed. The low certainty of the cumulative evidence reported to date suggests that further randomized comparisons of these surgical approaches would provide more precise estimates of effects but are unlikely to modify our conclusions. Future trials may elect to focus on participant-reported outcomes such as satisfaction with vision before and after surgery and effects of remaining visual aberrations, in addition to contrast sensitivity and clinical outcomes analyzed in this review.

Initial Outcomes with Customized Myopic LASIK, Guided by Automated Ray Tracing Optimization: A Novel Technique

Purpose

Safety and efficacy of a novel automated ray tracing optimization in customization of excimer ablation in myopic LASIK.

Methods

In a consecutive case series, 25 patients (50 eyes) undergoing femtosecond-laser-assisted myopic LASIK were evaluated. The novel, artificial-intelligence platform initially calculates the ablation profile based on a model eye for each case, based on interferometry axial length data. Low- and high-order aberration calculation is performed by raytracing based on wavefront and Scheimpflug tomography measurements, all from a single diagnostic device. Visual acuity, refractive error, keratometry, topography, high-order aberrations and contrast sensitivity were evaluated, over six months follow-up.

Results

Change from pre- to 6 months post-operative: mean refractive error improved from −5.06 ± 2.54 diopters (D) (range −8.0 to −0.50 D) to −0.11 ± 0.09 D (range −0.25 to + 0.25); refractive astigmatism from −1.07 ± 0.91 D (range −4.25 to 0 D) to −0.15 ± 0.04 D (range −0.25 to 0); and topographic astigmatism from −1.65 ± 0.85 D to −0.26 ± 0.11 D (range −0.60 to 0). About 65% of eyes gained one line of vision and 38% 2 lines. Pre- to post-operative high-order aberration average: RMSh changed from 0.25 um to 0.35 um. Contrast sensitivity improved post-operatively.

Conclusion

We report safe and effective preliminary outcomes with a novel excimer laser customization by ray tracing optimization, for myopic LASIK treatments, employing several independent up-till-now diagnostics and a customized eye model reference for each case. It bears the potential advantage through total eye aberration data and ray tracing refraction calculation to offer improved and more predictable visual outcomes.

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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.

Refractive surgery beyond 2020

Refractive surgery refers to any procedure that corrects or minimizes refractive errors. Today, refractive surgery has evolved beyond the traditional laser refractive surgery, embodied by the popular laser in situ keratomileusis or 'LASIK'. New keratorefractive techniques such as small incision lenticule extraction (SMILE) avoids corneal flap creation and uses a single laser device, while advances in surface ablation techniques have seen a resurgence in its popularity. Presbyopic treatment options have also expanded to include new ablation profiles, intracorneal implants, and phakic intraocular implants. With the improved safety and efficacy of refractive lens exchange, a wider variety of intraocular lens implants with advanced optics provide more options for refractive correction in carefully selected patients. In this review, we also discuss possible developments in refractive surgery beyond 2020, such as preoperative evaluation of refractive patients using machine learning and artificial intelligence, potential use of stromal lenticules harvested from SMILE for presbyopic treatments, and various advances in intraocular lens implants that may provide a closer to 'physiological correction' of refractive errors.

Comparison of clinical outcomes between wavefront-optimized versus corneal wavefront-guided transepithelial photorefractive keratectomy for myopic astigmatism

PURPOSE

To evaluate and compare the clinical outcomes, including visual acuity, refractive errors, and aberrations, between aberration-free transepithelial photorefractive keratectomy (PRK) and corneal wavefront-guided transepithelial PRK in eyes with myopic astigmatism.

SETTING

Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, South Korea.

DESIGN

Retrospective comparative case series.

METHODS

Patients with myopic astigmatism were treated with aberration-free transepithelial PRK or corneal wavefront-guided transepithelial PRK using a 1050 Hz high-repetition excimer laser. The safety, efficacy, predictability, and corneal aberrations were compared preoperatively and 1, 2, 3, and 6 months postoperatively.

RESULTS

The study comprised 188 patients (188 eyes); 91 eyes had aberration-free transepithelial PRK and 97 eyes corneal wavefront-guided transepithelial PRK. Six month after surgery, the mean uncorrected distance visual acuity was comparable (-0.06 logMAR ± 0.07 [SD] aberration-free group; -0.06 ± 0.06 logMAR wavefront-guided group). The safety, efficacy, and predictability of refractive and visual outcomes were also comparable between groups. Corneal total root-mean-square (RMS) higher-order aberrations (HOAs) increased after treatment in both groups, although fewer RMS HOAs were induced in the corneal wavefront-guided group than in the aberration-free group. Spherical aberration increased similarly after treatment in both groups. However, coma and trefoil increased only in the aberration-free group.

CONCLUSIONS

Aberration-free transepithelial PRK and corneal wavefront-guided transepithelial PRK were safe and effective for correction of myopic astigmatism without difference in visual acuity and refractive outcomes. However, the corneal wavefront-guided profile induced fewer corneal aberrations than the aberration-free profile.

Comparison of Wavefront-Optimized Ablation and Topography-Guided Contoura Ablation With LYRA Protocol in LASIK

PURPOSE

To compare the refractive outcomes and aberration data analysis of wavefront-optimized (WFO) ablation and topography-guided Contoura ablation (TGCA) (Contoura on the WaveLight laser; WaveLight GmbH, Erlangen, Germany) in patients who had laser-assisted in situ keratomileusis (LASIK) for myopia or myopic astigmatism.

METHODS

In this comparative contralateral eye study, patients who underwent LASIK with TGCA in one eye and with WFO ablation in the fellow eye were analyzed. Aberration measurements and corneal topography were analyzed using the WaveLight Oculyzer II diagnostic device (Alcon Laboratories, Inc., Fort Worth, TX). Total corneal higher order aberrations (HOAs) including vertical and oblique astigmatism (Z² ₂, Z² _-2), coma (Z³ ₁, Z³ _-1), trefoil (Z³ ₃, Z³ _-3), spherical aberration, and Q value were analyzed. These measurements were taken preoperatively and 3 months postoperatively.

RESULTS

This study comprised 32 patients. There were no significant differences between both procedures according to postoperative uncorrected and corrected distance visual acuity values, refractive errors, and manifest refraction spherical equivalents within ±0.50 diopters (D) of emmetropia (P > .05). The preoperative corneal HOAs and Q values were also similar between the groups (P > .05). At 3 months postoperatively, the vertical and horizontal coma values in the WFO ablation group were statistically significantly higher compared to the TGCA group (P = .013 and .020, respectively). Less stromal tissue was ablated in the TGCA group compared to the WFO ablation group (P < .001).

CONCLUSIONS

Although WFO ablation and TGCA protocols had statistically similar visual outcomes, the TGCA protocol was associated with a significantly lower induction in vertical and horizontal coma and smaller amount of tissue ablation compared to WFO ablation. [J Refract Surg. 2019;35(4):222-229.].

Refractive surgery

Refractive surgery has evolved beyond laser refractive techniques over the past decade. Laser refractive surgery procedures (such as laser in-situ keratomileusis), surface ablation techniques (such as laser epithelial keratomileusis), and photorefractive keratectomy have now been established as fairly safe procedures that produce excellent visual outcomes for patients with low-to-moderate amounts of ametropia. Additionally, a broader selection of options are now available to treat a wider range of refractive errors. Small incision lenticule extraction uses a femtosecond laser to shape a refractive lenticule, which is removed through a small wound. The potential advantages of this procedure include greater tectonic strength and less dry eye. In the future, intracorneal implants could be used to treat hyperopia or presbyopia. Phakic intraocular implants and refractive lens exchange might be useful options in carefully selected patients for correcting high degrees of ametropia. Thus, physicians are now able to provide patients with the appropriate refractive corrective option based on the individual's risk-benefit profile.

Outcomes of topography-guided versus wavefront-optimized laser in situ keratomileusis for myopia in virgin eyes

PURPOSE

To compare the outcomes of topography-guided and wavefront-optimized treatment in patients having laser in situ keratomileusis (LASIK) for myopia.

SETTING

Advanced Eye Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India.

DESIGN

Prospective contralateral-eye case study.

METHODS

Patients had topography-guided LASIK in 1 eye and wavefront-optimized LASIK in the contralateral eye using the Customized Refractive Surgery Master software and Mel 80 excimer laser. Refractive (residual manifest refraction spherical equivalent [MRSE], higher-order aberrations [HOAs]), and visual (uncorrected distance visual acuity [UDVA] and photopic and mesopic contrast sensitivity) outcomes were prospectively analyzed 6 months postoperatively.

RESULTS

The study comprised 35 patients. The UDVA was 0.0 logMAR or better and the postoperative residual MRSE was ±0.50 diopter in 94.29% of eyes in the topography-guided group and 85.71% of eyes in the wavefront-optimized group (P = .09). More eyes in the topography-guided group than in the wavefront-optimized group had a UDVA of -0.1 logMAR or better (P = .04). Topography-guided LASIK was associated with less deterioration of mesopic contrast sensitivity at higher spatial frequencies (12 cycles per degree [cpd] and 18 cpd) and lower amounts of induced coma (P = .04) and spherical aberration (P = .04). Less stromal tissue was ablated in the topography-guided group (mean 61.57 μm ± 16.23 [SD]) than in the wavefront-optimized group (mean 79.71 ± 14.81 μm) (P < .001).

CONCLUSION

Although topography-guided LASIK and wavefront-optimized LASIK gave excellent results, topography-guided LASIK was associated with better contrast sensitivity, lower induction of HOAs, and a smaller amount of tissue ablation.

FINANCIAL DISCLOSURE

None of the authors has a financial or proprietary interest in any material or method mentioned.

Predictive Factors for Successful High Myopia Treatment Using High-Frequency Laser-In-Situ Keratomileusis

Aim

To evaluate the predictive factors of LASIK procedure for high myopia with or without astigmatism using a combination of high-frequency femtosecond-assisted LASIK followed by an excimer laser.

Methods

This study was a retrospective interventional case series study to evaluate myopic eyes undergoing high platform LASIK with FEMTO LDV Z2 intervention, followed by WaveLight®EX500 excimer laser machine. Subjects were divided into 2 groups: high myopia (SE of -6.01 to -9.00 D) and very high myopia (SE of -9.01 D or higher). Myopic eyes (Spherical Equivalent/SE) less than -13 D were included in this study. Visual Acuity (VA) was evaluated 1 day and 60 days after the procedure. Predictive factors, such as age, degree of sphere, degree of astigmatism, keratometric reading and axial length were analyzed to detect any influences affecting the final VA results.

Results

A total of 316 myopia eyes underwent intervention, mean age: 25.3±3.8 years. Target treatment was achieved in 96.1% of patients with high myopia and 69.9% of patients with very high myopia. High degree of sphere and astigmatism constitutes an important factor influencing final VA.

Conclusion

Modern machines provide a more promising efficacy and success of LASIK procedure in high myopia: important predictive factors were a high degree of sphere and astigmatism for achieving the optimal final outcome.

Comparison between Wavefront-optimized and corneal Wavefront-guided Transepithelial photorefractive keratectomy in moderate to high astigmatism

BACKGROUND

To compare the clinical outcomes of wavefront-optimized (WFO) transepithelial photorefractive keratectomy (trans-PRK) and corneal wavefront-guided (CWFG) trans-PRK for myopic eyes with moderate to high astigmatism.

METHODS

One hundred ninety-six eyes (196 patients) with moderate to high astigmatism (≥ 1.75 D) treated with WFO or CWFG trans-PRK (101 and 95 eyes, respectively) were retrospectively registered. Safety, efficacy, predictability, vector analysis, and corneal aberrations were compared between groups preoperatively and at 6 months postoperatively.

RESULTS

At postoperative 6 months, the mean logMAR uncorrected distance visual acuity was similar in the WFO (- 0.07 ± 0.08) and CWFG (- 0.07 ± 0.07) groups. Safety, efficacy, and predictability of refractive and visual outcomes were also similar. The correction indices were 1.02 ± 0.14 and 1.03 ± 0.13 in the WFO and CWFG groups, respectively, with no significant difference. The absolute values of the angle of error were significantly higher in the WFO group (2.28 ± 2.44 vs. 1.40 ± 1.40; P = 0.002). Corneal total root mean square higher-order aberrations and corneal spherical aberrations increased postoperatively in both groups; however, the change was smaller in the CWFG group. Corneal coma showed a significant increase postoperatively only in the WFO group.

CONCLUSIONS

WFO and CWFG trans-PRK are safe and effective for correcting moderate to high astigmatism. However, CWFG trans-PRK provides a more predictable astigmatism correction axis and fewer induced corneal aberrations.

Comparing corneal higher-order aberrations in corneal wavefront-guided transepithelial photorefractive keratectomy versus small-incision lenticule extraction

PURPOSE

To evaluate the changes in corneal higher-order aberrations (HOAs) after corneal wavefront-guided transepithelial photorefractive keratectomy (PRK) and small-incision lenticule extraction (SMILE).

SETTING

Yonsei University College of Medicine and Eyereum Eye Clinic, South Korea.

DESIGN

Retrospective case series.

METHODS

Medical records of patients having either corneal wavefront-guided transepithelial PRK or small-incision lenticule extraction were examined. The root-mean-square total HOAs, 3rd-order coma aberration, and 4th-order spherical aberration were measured preoperatively and 6 months postoperatively. Independent t tests and analysis of covariance were used to compare changes in corneal HOAs between the 2 groups.

RESULTS

The study comprised 77 eyes having corneal wavefront-guided transepithelial PRK and 81 eyes having small-incision lenticule extraction. The total HOAs and spherical aberration increased after transepithelial PRK (all P < .001), whereas coma aberration was stable after transepithelial PRK. The total HOAs, spherical aberration, and coma aberration increased after small-incision lenticule extraction (P < .001 for total HOAs, spherical aberration; P = .004 for coma). At 6 months postoperatively, total HOAs and spherical aberration were significantly larger in the transepithelial PRK group than in the small-incision lenticule extraction group. Coma aberration was larger in the small-incision lenticule extraction group than in the transepithelial PRK group. Spherical aberration induction was significantly smaller in the small-incision lenticule extraction group than in the transepithelial PRK group (P < .001), and coma aberration induction was larger in the small-incision lenticule extraction group than in the transepithelial PRK group (P = .011).

CONCLUSIONS

Small-incision lenticule extraction demonstrated that the induction of total HOAs was comparable to corneal wavefront-guided transepithelial PRK, accompanied by smaller spherical aberration induction and larger coma aberration induction. During small-incision lenticule extraction, surgeons should aim to obtain optimum centration for smaller induction of corneal HOAs.

Comparing aspheric ablation profile with standard corneal ablation for correction of myopia and myopic astigmatism, a contralateral eye study

The purpose of this study is to compare visual outcomes of myopic refractive surgery, using tissue saving (TS), a standard ablation profile by a Technolas 217z100, and aberration smart ablation (ASA), an aspheric algorithm by a MEL 80 excimer laser in two eyes of one patient. In this prospective interventional paired-eye controlled study, a total of 100 eyes of 50 participants with myopia with or without astigmatism underwent thin-flap Femto-LASIK, using a Femto LDV femtosecond laser (Ziemer Ophthalmic Systems AG, Port, Switzerland). For each patient, one eye was randomly treated with tissue-saving algorithm (TS group) by the Technolas 217z100 excimer laser and the other eye was treated with optimized smart ablation profile (ASA group) by the MEL 80 excimer laser. Outcome measures were uncorrected distance visual acuities (UDVAs), corrected distance visual acuities (CDVAs), manifest refraction, higher-order aberrations (HOAs), contrast sensitivity, and patient satisfaction 12 months after surgery. At 12 months postoperative, "45 subjects returned with mean" UDVA was - 0.02 ± 0.08 Logarithm of mean angle of resolution (LogMAR) for TS group and - 0.02 ± 0.09 LogMAR for ASA group (P = 0.91). Of the TS eyes, 42/45 (93.3%) and 32/45 (71.1%) were within ± 0.5 D and ± 0.25 D of target refraction, respectively, and of the ASA eyes, 41/45 (91.1%) and 30/45 (66.6%) were within ± 0.5 D and ± 0.25 D of target refraction, respectively. No statistically significant differences were observed between groups in HOAs changes and contrast sensitivity function. Aspheric and non-aspheric LASIKs using the two different excimer lasers provide similar results in myopic and myopic astigmatism patients.

Treatment of moderate-to-high hyperopia with the WaveLight Allegretto 400 and EX500 excimer laser systems

Purpose

To evaluate the efficacy of treating patients with +3.00 diopters (D) to +6.00 D of hyperopia via laser-assisted in situ keratomileusis (LASIK) with the WaveLight Allegretto 400 and EX500 excimer laser systems.

Setting

Private clinical ophthalmology practice.

Patients and methods

This was a retrospective study of patients undergoing LASIK treatments of +3.00 to +6.00 D on two different WaveLight laser systems: 163 eyes on the 400 (Hertz) Hz system and 54 eyes on the 500 Hz system. The duration of follow-up was 6 months postoperation. Data were evaluated for uncorrected distance visual acuity, corrected distance visual acuity (CDVA), spherical equivalents (SEQs), and changes in these parameters (eg, loss of vision, regression over time).

Results

Treatment with both lasers was safe and effective, with loss of one line of CDVA in four of 162 eyes using the 400 Hz laser system, and none of the 54 eyes with the 500 Hz laser system. Overall, regression ≥0.75 D from goal at 6 months was observed in 11.7% (19/163) of eyes in the 400 Hz laser group and 9.26% (5/54) of eyes in the 500 Hz laser group (regression ≥0.50 D =77.9% [127/163] and 77.8% [42/54], respectively). The mean SEQ regressions for all eyes with moderate hyperopia were 0.10 and 0.18 D for those with high hyperopia.

Conclusions

Both the 400 and 500 Hz excimer laser systems were safe and effective for the LASIK treatment of moderate-to-high hyperopia. The overall rate of regression was low and the amount of regression was relatively small with both systems.

Effect of Iris registration on visual outcome in wavefront-guided LASEK for myopic astigmatism

PURPOSE

This study aimed to investigate the effect of iris registration (IR) on visual outcomes in wavefront-guided LASEK for myopic astigmatism.

METHODS

The retrospective chart review was performed for wavefront-guided LASEK using VISX Star S4 in patients with myopic astigmatism (cylinder ≥ 1.00 diopter[D]). Eyes were divided into IR group (LASEK with IR at the time of surgery) and Non-IR group (LASEK without IR system + failed-IR engagement during LASEK). Visual acuity (VA), astigmatism, higher-order aberration (HOA), and contrast sensitivity were assessed preoperatively and 3 months postoperatively. The IR and Non-IR groups were subcategorized depending on the spherical equivalent (lower myopia ≤-5.00 D vs. higher myopia >-5.00 D) for the comparison of HOA changes.

RESULTS

Postoperative uncorrected VAs showed no differences between IR (n = 30) and Non-IR (n = 46). In astigmatic vector analyses, no differences were noted in the mean magnitude of error and the mean angle of error between two groups. There were no differences in postoperative total HOA, spherical aberration (SA), coma, and trefoil between the groups, either. The total HOA and SA increased in both groups, while coma increased only in Non-IR. In higher myopia, ΔRMS of coma was smaller in IR. Preoperative and postoperative total HOA were linearly correlated in Non-IR, but not for IR. Contrast sensitivity of 12 cycles per degree improved in both groups.

CONCLUSION

IR had similar outcomes to conventional trackers in wavefront-guided LASEK, with less tendency of inducing coma, especially in higher myopia.

Topography-modified refraction (TMR): adjustment of treated cylinder amount and axis to the topography versus standard clinical refraction in myopic topography-guided LASIK

PURPOSE

To evaluate the safety, efficacy, and contralateral eye comparison of topography-guided myopic LASIK with two different refraction treatment strategies.

SETTING

Private clinical ophthalmology practice.

PATIENTS AND METHODS

A total of 100 eyes (50 patients) in consecutive cases of myopic topography-guided LASIK procedures with the same refractive platform (FS200 femtosecond and EX500 excimer lasers) were randomized for treatment as follows: one eye with the standard clinical refraction (group A) and the contralateral eye with the topographic astigmatic power and axis (topography-modified treatment refraction; group B). All cases were evaluated pre- and post-operatively for the following parameters: refractive error, best corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), topography (Placido-disk based) and tomography (Scheimpflug-image based), wavefront analysis, pupillometry, and contrast sensitivity. Follow-up visits were conducted for at least 12 months.

RESULTS

Mean refractive error was -5.5 D of myopia and -1.75 D of astigmatism. In group A versus group B, respectively, the average UDVA improved from 20/200 to 20/20 versus 20/16; post-operative CDVA was 20/20 and 20/13.5; 1 line of vision gained was 27.8% and 55.6%; and 2 lines of vision gained was 5.6% and 11.1%. In group A, 27.8% of eyes had over -0.50 diopters of residual refractive astigmatism, in comparison to 11.7% in group B (P<0.01). The residual percentages in both groups were measured with refractive astigmatism of more than -0.5 diopters.

CONCLUSION

Topography-modified refraction (TMR): topographic adjustment of the amount and axis of astigmatism treated, when different from the clinical refraction, may offer superior outcomes in topography-guided myopic LASIK. These findings may change the current clinical paradigm of the optimal subjective refraction utilized in laser vision correction.

Wavefront-guided versus wavefront-optimized photorefractive keratectomy: Clinical outcomes and patient satisfaction

PURPOSE

To compare visual outcomes following Visx Star S4 Customvue wavefront-guided and Allegretto Wave Eye-Q 400 Hz wavefront-optimized photorefractive keratectomy (PRK).

SETTING

Warfighter Refractive Eye Surgery Program and Research Center, Fort Belvoir, Virginia, and Walter Reed National Military Medical Center, Bethesda, Maryland, USA.

DESIGN

Prospective randomized clinical trial.

METHODS

Active-duty United States military soldiers were randomized to have wavefront-guided (Visx Star S4 Customvue) or wavefront-optimized PRK. Participants were followed up to 12 months postoperatively. Primary outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and manifest spherical equivalent (SE). Secondary outcome measures included refractive astigmatism, higher-order aberrations (HOAs), contrast sensitivity, subjective visual complaints, and patient satisfaction.

RESULTS

The study evaluated 108 soldiers (mean age 30.3 years ± 6.3 [SD]; mean manifest SE -3.51 ± 1.63 D). At 12 months postoperatively, achieved UDVA, CDVA, manifest SE, and refractive astigmatism were comparable between wavefront-guided and wavefront-optimized groups (P > .213). Spherical aberration and total HOAs significantly increased from baseline in both groups (P < .006). The change in coma, trefoil, spherical aberration, and total HOAs (P > .254) were comparable between groups. There were fewer losses of photopic low-contrast visual acuity (LCVA) at 5% contrast after wavefront-guided compared to wavefront-optimized treatment (P = .003). There was no significant difference between treatment groups in visual symptoms, overall vision expectation, and satisfaction (P > .075).

CONCLUSION

Wavefront-guided treatment offered a small advantage in photopic LCVA. Refractive outcomes, HOAs, self-reported visual difficulties, overall vision expectation, and satisfaction were otherwise comparable between wavefront-guided and wavefront-optimized treatments.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Correlation of higher order aberrations and components of astigmatism in myopic refractive surgery candidates

Purpose

To evaluate the correlation between refractive, corneal, and residual astigmatism and higher order aberrations (HOA) in refractive surgery candidates.

Methods

Three hundred and seventy-five eyes of 188 patients aged 28.2 ± 6.24 years with a predominance of females (62.7%) were enrolled in this study. Refraction, topography (Orbscan IIz, Bausch & Lomb, Rochester, NY, USA), and aberrometry (Zywave, Bausch & Lomb, Rochester, NY, USA) were performed to determine refractive and corneal astigmatism and HOA for all participants. Ocular residual astigmatism was calculated using vector analysis.

Results

The mean spherical equivalent was −3.59 ± 1.95 D and the mean refractive astigmatism was −1.97 ± 1.3 D. The mean HOA was 0.38 ± 0.15 μm in all cases, which increased with spherical equivalent (p < 0.05). There was a positive significant correlation between both corneal and refractive astigmatism and HOA (p < 0.05), but there was no significant correlation between residual astigmatism and HOA (p = 0.122).

Conclusion

The results of the study showed significant correlations between corneal and refractive astigmatisms and HOA.

Wavefront-optimized surface retreatments of refractive error following previous laser refractive surgery: a retrospective study

Background

Retreatments are sometimes necessary to correct residual or induced refractive errors following refractive surgery. Many different combinations of primary treatment methods and retreatment techniques have been studied, however, few studies have investigated wavefront-optimized (WFO) technology for retreatment following primary refractive surgery. This study aimed to report the outcomes of WFO photorefractive keratectomy (PRK) retreatments of refractive error following previous laser refractive surgery with PRK, laser in situ keratomileusis (LASIK), or laser-assisted subepithelial keratectomy (LASEK).

Methods

We reviewed records of patients who underwent WFO PRK retreatments using the Allegretto Wave Eye-Q 400 Hz Excimer Laser System (Alcon Surgical) between January 2008 and April 2011 at Walter Reed Army Medical Center and Madigan Army Medical Center. Outcomes were recorded in terms of uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent (MRSE), corrected distance visual acuity (CDVA), and complications at 1 month (M), 3 M, and 6 M post-op.

Results

Seventy-eight patients (120 eyes) underwent WFO PRK retreatment during the study period. Primary surgery was surface ablation in 87 eyes (78 PRK, 9 LASEK) and LASIK in 33 eyes. The mean spherical equivalent before retreatment was −0.79 ± 0.94 D (−3.00 to 1.88 D). UDVA was ≥ 20/20 in 69 eyes (60.0 %) at 1 M, 54 eyes (71.1 %) at 3 M, and 27 eyes (73.0 %) at 6 M follow-up. MRSE was within ±0.50 D of emmetropia in 78 eyes (67.8 %) at 1 M, 59 eyes (77.6 %) at 3 M, and 25 eyes (67.6 %) at 6 M follow-up. CDVA was maintained within ±1 line of pre-op in 113 of 115 eyes (98.3 %) at 1 M, 74 of 76 eyes (97.4 %) at 3 M, and 37 eyes (100 %) at 6 M follow-up.

Conclusion

Although follow-up was limited beyond 3 M, WFO PRK retreatments in patients with residual refractive error may be a safe and effective procedure. Further studies are necessary to determine the long-term safety and stability of outcomes.

Image Quality Analysis of Eyes Undergoing LASER Refractive Surgery

Laser refractive surgery for myopia increases the eye’s higher-order wavefront aberrations (HOA’s). However, little is known about the impact of such optical degradation on post-operative image quality (IQ) of these eyes. This study determined the relation between HOA’s and IQ parameters (peak IQ, dioptric focus that maximized IQ and depth of focus) derived from psychophysical (logMAR acuity) and computational (logVSOTF) through-focus curves in 45 subjects (18 to 31yrs) before and 1-month after refractive surgery and in 40 age-matched emmetropic controls. Computationally derived peak IQ and its best focus were negatively correlated with the RMS deviation of all HOA’s (HORMS) (r≥-0.5; p<0.001 for all). Computational depth of focus was positively correlated with HORMS (r≥0.55; p<0.001 for all) and negatively correlated with peak IQ (r≥-0.8; p<0.001 for all). All IQ parameters related to logMAR acuity were poorly correlated with HORMS (r≤|0.16|; p>0.16 for all). Increase in HOA’s after refractive surgery is therefore associated with a decline in peak IQ and a persistence of this sub-standard IQ over a larger dioptric range, vis-à-vis, before surgery and in age-matched controls. This optical deterioration however does not appear to significantly alter psychophysical IQ, suggesting minimal impact of refractive surgery on the subject’s ability to resolve spatial details and their tolerance to blur.

Comparison of corneal shape changes and aberrations induced By FS-LASIK and SMILE for myopia

PURPOSE

To compare corneal curvatures, corneal power calculations, and higher-order aberrations (HOAs) of femtosecond laser-assisted LASIK (FS-LASIK) with small incision lenticule extraction (SMILE) following surgery for moderate to high myopia.

METHODS

A retrospective study of 736 eyes of 368 patients treated with SMILE and 148 eyes of 74 patients treated with FS-LASIK. Preoperative mean spherical equivalent was -7.3 ± 1.5 diopters in the SMILE group and -7.6 ± 1.3 diopters in the FS-LASIK group. Corneal curvatures, corneal power calculations performed by ray tracing, and HOAs measured with Scheimpflug technology before and 3 months after surgery were analyzed.

RESULTS

Corneal curvatures changed significantly in the anterior corneal surface, but not in the posterior corneal surface, in both groups; after SMILE, the sagittal curvature was constant for the central 4-mm diameter, in contrast to FS-LASIK where the curvature showed a gradual steepening with increasing diameter. Corneal power calculations were different across the cornea depending on the measurement diameter between the two groups postoperatively. Measured over a 5-mm zone on the total cornea, FS-LASIK induced 0.11 µm more coma (P < .001) and 0.13 µm higher spherical aberration (P < .001) as compared to SMILE; similar results in other HOAs were seen for the anterior corneal surface. Negligible differences in HOAs were induced on the posterior corneal surface.

CONCLUSIONS

SMILE and FS-LASIK produced distinct changes in anterior corneal shape evident in different postoperative corneal curvatures and power measurements between the two groups. Postoperative HOAs were much lower after SMILE as compared to FS-LASIK.

Biomechanics of the cornea evaluated by spectral analysis of waveforms from ocular response analyzer and Corvis-ST

PURPOSE

In this study, spectral analysis of the deformation signal from Corvis-ST (CoST) and reflected light intensity from ocular response analyzer (ORA) was performed to evaluate biomechanical concordance with each other.

METHODS

The study was non-interventional, observational, cross-sectional and involved 188 eyes from 94 normal subjects. Three measurements were made on each eye with ORA and CoST each and then averaged for each device. The deformation signal from CoST and reflected light intensity (applanation) signal from ORA was compiled for all the eyes. The ORA signal was inverted about a line joining the two applanation peaks. All the signals were analyzed with Fourier series. The area under the signal curves (AUC), root mean square (RMS) of all the harmonics, lower order (LO included 1st and 2nd order harmonic), higher order (HO up to 6th harmonic), CoST deformation amplitude (DA), corneal hysteresis (CH) and corneal resistance factor (CRF) were analyzed.

RESULTS

The device variables and those calculated by Fourier transform were statistically significantly different between CoST and ORA. These variables also differed between the eyes of the same subject. There was also statistically significant influence of eyes (left vs. right) on the differences in a sub-set of RMS variables only. CH and CRF differed statistically significantly between the eyes of subject (p<0.001) but not DA (p = 0.65).

CONCLUSIONS

CoST was statistically significantly different from ORA. CoST may be useful in delineating true biomechanical differences between the eyes of a subject as it reports deformation.

Prospective randomized contralateral eye evaluation of subjective quality of vision after wavefront-guided or wavefront- optimized photorefractive keratectomy

PURPOSE

To compare the effect of wavefront-guided (WFG) and wavefront-optimized (WFO) photorefractive keratectomy (PRK) on patient perceived quality of vision.

METHODS

Seventy-one patients (142 eyes) were enrolled in this prospective, randomized, fellow eye controlled study. One eye was randomized to undergo WFG PRK treatment by the AMO Visx CustomVue S4 IR excimer laser system (Abbott Medical Optics, Inc., Santa Clara, CA) and the fellow eye received WFO PRK treatment by the Alcon Allegretto Wave Eye-Q 400 Hz excimer laser system (Alcon Laboratories, Inc., Fort Worth, TX). Patients answered questionnaires on their visual symptoms and quality of vision preoperatively and at 1, 3, 6, and 12 months after surgery.

RESULTS

Patients in both groups reported better vision compared to baseline from 3 months onward (mean change in score of 1.56 to 2.51 in the WFO group and 1.54 to 2.28 in the WFG group, P ⩽ .003). Both groups experienced less nighttime glare from 6 months onward (P ⩽ .030). Halos, double vision, and visual clarity were initially worse (P ⩽ .025) but not significantly different after 1 month. Haze and fluctuating vision resolved after 3 months. Visual symptoms were similar between the two groups at all times (P ⩾ .059) except at 6 months, when patients felt their WFG eyes had more excellent vision (P = .029). A composite of all symptoms was also similar between the groups until 12 months when patients had fewer symptoms in their WFO eye (P = .044).

CONCLUSIONS

One year after surgery, patient self-reported visual symptoms were not significantly different in eyes receiving WFG or WFO PRK. However, the average of all symptoms was lower in eyes receiving wavefront-optimized treatment.

Long-term bladeless LASIK outcomes with the FS200 Femtosecond and EX500 Excimer Laser workstation: the Refractive Suite

Purpose

The evaluation of the safety, efficacy, and long-term stability of LASIK procedures utilizing novel platform comprising a femtosecond and excimer laser and multiple networked diagnostics.

Setting

Private clinical ophthalmology practice.

Patients and methods

In consecutive cases of myopic LASIK procedure with a novel refractive platform (FS200 Femtosecond and EX500 Excimer Laser), 190 eyes (from 109 different patients) were evaluated pre- and postoperatively for the following parameters: refractive error, best corrected distance visual acuity, uncorrected distance visual acuity, topography (Placido-disc based) and tomography (Scheimpflug-image based), wavefront analysis, pupillometry, and contrast sensitivity. Follow-up visits were conducted for at least 12 months.

Results

The change from pre- to postoperative mean refractive error was from −5.29 ± 2.39 diopters (D) (range −8.0 to −0.50 D) to −0.27 ± 0.09 D at the 3-month visit, −0.27 ± 0.10 D at the 6-month visit, and −0.39 ± 0.08 D at the 1-year visit. The change from pre- to postoperative refractive astigmatism was −1.07 ± 0.91 D (range −4.25 to 0 D) to −0.14 ± 0.04 D at 3 months, −0.15 ± 0.04 at 6 months, and −0.16 ± 0.04 at the 1-year visit. The proportion of the eyes with postoperative astigmatism within 0.5 D ranged between 95.6% and 99%. The proportion of eyes achieving uncorrected distance visual acuity of 1.0 (decimal) was 93.0%.

Conclusion

The myopic LASIK clinical results with the FS200 Femtosecond Laser and EX500 Excimer Laser showed outstanding efficacy, great safety, and long-term stability.