Wavefront-guided versus non-wavefront-guided photorefractive keratectomy for myopia: meta-analysis of randomized controlled trials

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.

Characteristics of corneal high-order aberrations in adolescents with mild to moderate myopia

Background

This study investigated the characteristics of corneal higher-order aberrations (HOAs) of the anterior surface, posterior surface, and total cornea in adolescents with mild to moderate myopia.

Methods

A total of 183 patients with myopia (183 eyes) aged 8 to 18 years were enrolled in this study. The axial length (AL) of the eyes was measured by an IOL-Master, and corneal curvatures (K-values) and HOAs were measured by a Pentacam anterior segment diagnostic analyzer.

Results

Results of this study showed that the anterior, posterior and total corneal horizontal coma Z₃¹ were − 0.1249 ± 0.105 μm, 0.0009 ± 0.001 μm, and − 0.1331 ± 0.116 μm, respectively; the anterior, posterior and total corneal vertical coma Z₃^− 1 were − 0.0212 ± 0.164 μm, 0.0003 ± 0.043 μm, and − 0.0216 ± 0.168 μm, respectively; and spherical aberration (SA) Z₄⁰ values were 0.2244 ± 0.091 μm, 0.1437 ± 0.029 um, and 0.1889 ± 0.090 μm, respectively. Total corneal Z₃¹ was statistically correlated with posterior corneal astigmatism (K₂b − K₁b) (p = 0.038). Total corneal Z₃^− 1 was correlated with anterior corneal astigmatism (K₂f − K₁f) (p = 0.027). Anterior, posterior, and total corneal Z₄⁰ were correlated with anterior and posterior corneal curvature (K₁f, K₂f, K₁b, K₂b) (p = 0.001). Posterior corneal Z₄⁰b was also significantly correlated with AL.

Conclusions

In adolescents with mild to moderate myopia, the posterior corneal surface shape may play a compensatory role in the balance of corneal aberrations, and the posterior corneal SA tended to become less negative as the AL increased. The corneal coma may also play a compensatory role in posterior corneal surface astigmatism, which was valuable for the treatment for improving visual quality. This conclusion still needs to be verified.

Vector Analysis of 1-Year Astigmatic Outcomes From a Randomized Fellow Eye Comparison of Photorefractive Keratectomy Using 2 Excimer Laser Platforms

OBJECTIVE

To compare the astigmatic outcomes of photorefractive keratectomy (PRK) with a wavefront-guided (WFG) and a wavefront-optimized (WFO) excimer laser performed on two different platforms.

METHODS

Setting: institutional.

DESIGN

Prospective, randomized, fellow eye comparison clinical trial.

PARTICIPANTS

A total of 142 eyes of 71 patients with myopia of 12 diopters (D) or less and astigmatism of 3D or less were enrolled at the Byers Eye Institute at Stanford between April 2009 and March 2011.

INTERVENTION

One eye of each patient underwent WFG-PRK with the VISX CustomVue Star S4 IR (Abbott Medical Optics, Abbott Park, IL) and the contralateral eye underwent WFO-PRK with the Wavelight Allegretto Eye-Q 400-Hz laser platform (Alcon, Inc., Hüenberg, Switzerland). Alpins vector analysis of astigmatism was performed using manifest refraction measured preoperatively and 12 months postoperatively and vertexed to the corneal plane. Eyes were stratified for subgroup analysis based on preoperative manifest astigmatism.

RESULTS

WFG-PRK and WFO-PRK were similar regarding surgically induced astigmatism, difference vector, magnitude of error, correction index, flattening index, and index of success. The angle of error was 60% less in the WFG group compared with the WFO group (4.9±1.1° vs. 11.8±2.4°, P=0.01).

CONCLUSIONS

WFG-PRK with the VISX CustomVue Star S4 IR and WFO-PRK with the Alcon WaveLight Allegretto Eye-Q 400-Hz excimer laser platform produce similar astigmatic results in myopic patients; however, the WFG mode may produce slightly more predictable astigmatic corrections.

The quality of systematic reviews about interventions for refractive error can be improved: a review of systematic reviews

BACKGROUND

Systematic reviews should inform American Academy of Ophthalmology (AAO) Preferred Practice Pattern® (PPP) guidelines. The quality of systematic reviews related to the forthcoming Preferred Practice Pattern® guideline (PPP) Refractive Errors & Refractive Surgery is unknown. We sought to identify reliable systematic reviews to assist the AAO Refractive Errors & Refractive Surgery PPP.

METHODS

Systematic reviews were eligible if they evaluated the effectiveness or safety of interventions included in the 2012 PPP Refractive Errors & Refractive Surgery. To identify potentially eligible systematic reviews, we searched the Cochrane Eyes and Vision United States Satellite database of systematic reviews. Two authors identified eligible reviews and abstracted information about the characteristics and quality of the reviews independently using the Systematic Review Data Repository. We classified systematic reviews as "reliable" when they (1) defined criteria for the selection of studies, (2) conducted comprehensive literature searches for eligible studies, (3) assessed the methodological quality (risk of bias) of the included studies, (4) used appropriate methods for meta-analyses (which we assessed only when meta-analyses were reported), (5) presented conclusions that were supported by the evidence provided in the review.

RESULTS

We identified 124 systematic reviews related to refractive error; 39 met our eligibility criteria, of which we classified 11 to be reliable. Systematic reviews classified as unreliable did not define the criteria for selecting studies (5; 13%), did not assess methodological rigor (10; 26%), did not conduct comprehensive searches (17; 44%), or used inappropriate quantitative methods (3; 8%). The 11 reliable reviews were published between 2002 and 2016. They included 0 to 23 studies (median = 9) and analyzed 0 to 4696 participants (median = 666). Seven reliable reviews (64%) assessed surgical interventions.

CONCLUSIONS

Most systematic reviews of interventions for refractive error are low methodological quality. Following widely accepted guidance, such as Cochrane or Institute of Medicine standards for conducting systematic reviews, would contribute to improved patient care and inform future research.

Four-year follow-up of corneal aberrations and visual functions of myopic patients after laser in situ keratomileusis

Objective:

To report on 4-year follow-up of corneal higher-order aberrations and daily visual functions of myopic patients after laser in situ keratomileusis (LASIK).

Methods:

One hundred thirty four eyes of 67 patients who underwent LASIK guided by aspherical ablation were included in this study. The vision, corneal spherical aberration (SphA) and Coma were recorded before LASIK and at 6 month and 4 year after LASIK. The evaluation of the questionnaire about daily visual functions was performed by the same physician after LASIK.

Results:

No eye decreased the BCVA during 4 year follow-up. The effect index and safety index were 1.08±0.16, 1.11±0.17 and 1.12±0.16, 1.13±0.14 respectively at 6 month and 4 year post-LASIK. After LASIK the corneal SphA and Coma were significantly increased, however the difference between 6 month and 4 year post-LASIK was no statistical significance. Most patients (94.3%-92.4%) felt satisfaction or high satisfaction about the ability to perform each daily visual function after LASIK. Meanwhile there was still about 7.4%-9.2% patients who complained that they could not drive at night. Further analysis showed that the score of driving at night was negative correlation with corneal SphA (r=-0.645, p=0.040; r=-0.688, p=0.040 at 6 month and 4 year post-LASIK respectively).

Conclusions:

Our four-year follow-up outcomes indicated that the myopic patients after LASIK had the long-term stable corneal aberration and satisfaction of daily visual functions.