Journal of Refractive Surgery

Original Article Supplemental Data

One-Year Outcomes From a Prospective, Randomized, Eye-to-Eye Comparison of Wavefront-Guided and Wavefront-Optimized PRK in Myopia

Ryan G. Smith, MD; Edward E. Manche, MD

Abstract

PURPOSE:

To compare wavefront-guided (WFG) and wavefront-optimized (WFO) photorefractive keratectomy (PRK) in patients with myopia using objective and self-reported quality of vision outcomes.

METHODS:

A total of 40 eyes from 20 participants were prospectively randomized to receive WFG or WFO PRK with the WaveLight Allegretto Eye-Q 400-Hz excimer laser (Alcon Laboratories, Inc., Fort Worth, TX). The primary outcome measured was uncorrected distance visual acuity (UDVA) at 12 months postoperatively. Secondary outcome measures included corrected distance visual acuity (CDVA), less than 5% and less than 25% contrast visual acuity, changes in higher order aberrations (HOAs), and self-reported quality of vision. Patients completed a validated, Rasch-tested, linear-scaled 30-item questionnaire assessing the quality of vision and visual symptoms preoperatively and at each visit.

RESULTS:

There was no statistically significant difference (P > .05) between the WFG and WFO groups in the frequency of attaining a refractive error within ±0.25 diopters of emmetropia, achieving postoperative UDVA of 20/16 or better or 20/20 or better, losing one or two or more lines or maintaining their preoperative CDVA, or differences in UDVA, CDVA, low contrast acuity, or HOAs. None of the measured quality of vision parameters exhibited statistically significant differences between the groups preoperatively or at 12 months postoperatively (all P > .05). The WFG and WFO groups each showed significant improvement in multiple subjective measures compared to pretreatment values in the same eye. A total of 12.5% of patients preferred their WFG PRK eye, 31.25% preferred their WFO PRK eye, and 56.25% had no preference at 12 months postoperatively.

CONCLUSIONS:

WFG and WFO PRK using the Alcon Wave-Light Allegretto Eye-Q 400-Hz excimer laser platform provide similar results and self-reported visual symptoms in myopic eyes at 12 months postoperatively.

[J Refract Surg. 2020;36(3):160–168.]

Abstract

PURPOSE:

To compare wavefront-guided (WFG) and wavefront-optimized (WFO) photorefractive keratectomy (PRK) in patients with myopia using objective and self-reported quality of vision outcomes.

METHODS:

A total of 40 eyes from 20 participants were prospectively randomized to receive WFG or WFO PRK with the WaveLight Allegretto Eye-Q 400-Hz excimer laser (Alcon Laboratories, Inc., Fort Worth, TX). The primary outcome measured was uncorrected distance visual acuity (UDVA) at 12 months postoperatively. Secondary outcome measures included corrected distance visual acuity (CDVA), less than 5% and less than 25% contrast visual acuity, changes in higher order aberrations (HOAs), and self-reported quality of vision. Patients completed a validated, Rasch-tested, linear-scaled 30-item questionnaire assessing the quality of vision and visual symptoms preoperatively and at each visit.

RESULTS:

There was no statistically significant difference (P > .05) between the WFG and WFO groups in the frequency of attaining a refractive error within ±0.25 diopters of emmetropia, achieving postoperative UDVA of 20/16 or better or 20/20 or better, losing one or two or more lines or maintaining their preoperative CDVA, or differences in UDVA, CDVA, low contrast acuity, or HOAs. None of the measured quality of vision parameters exhibited statistically significant differences between the groups preoperatively or at 12 months postoperatively (all P > .05). The WFG and WFO groups each showed significant improvement in multiple subjective measures compared to pretreatment values in the same eye. A total of 12.5% of patients preferred their WFG PRK eye, 31.25% preferred their WFO PRK eye, and 56.25% had no preference at 12 months postoperatively.

CONCLUSIONS:

WFG and WFO PRK using the Alcon Wave-Light Allegretto Eye-Q 400-Hz excimer laser platform provide similar results and self-reported visual symptoms in myopic eyes at 12 months postoperatively.

[J Refract Surg. 2020;36(3):160–168.]

Although effective at correcting simple spherocylindrical refractive errors, conventional laser refractive surgery potentially can have the undesirable effects of inducing spherical aberrations and reducing vision quality. When performing conventional photorefractive keratectomy (PRK), the excimer laser pulses delivered to the periphery of the cornea have a decreased ablation effect because of their oblique angle of incidence on the corneal surface compared with centrally delivered pulses. This causes the cornea to be more oblate than prolate, thereby inducing more spherical aberration.1–5 Wavefront-based treatments attempt to compensate for this phenomenon with more sophisticated ablation algorithms and can be classified into two broad categories: wavefront-optimized (WFO) and wavefront-guided (WFG) algorithms. WFO algorithms consider the eye's refractive error, preoperative keratometry, and other related factors to render a treatment plan that applies more ablation to the peripheral cornea to compensate for energy loss and reflections. The goal of this treatment algorithm is to minimize the transition zone while maintaining the natural aspheric shape of the cornea to reduce the induction of higher order aberrations (HOAs). WFG algorithms are computed for a given eye based on its unique preoperative aberrometry results to develop a customized treatment plan that aims not only to ameliorate induced postoperative aberrations, but also to reduce or eliminate preoperative HOAs. The WaveLight Allegretto Eye-Q 400-Hz laser system (Alcon Laboratories, Inc., Fort Worth, TX) features both WFO and WFG approaches to treatment. The WFO approach applies a precalculated spherical aberration pattern to produce an aspherical ablation profile. The WFG approach builds an ablation pattern based on the individualized preoperative assessment of the total aberrations of a given eye using an aberrometer.1–5

Multiple studies have compared WFG with WFO platforms in laser in situ keratomileusis (LASIK) surgery.6–12 Several studies suggest that there are advantages to performing LASIK with WFG platforms, but other studies have suggested that there are no significant benefits to WFG over WFO LASIK.6–13 However, many of these investigations have been limited by small sample sizes and subject-to-subject designs, which are confounded by differences in wound healing and corneal biomechanical factors between patients. Few studies have addressed WFG versus WFO platforms for PRK surgery. Our group previously compared the algorithm using different laser platforms.14 However, no data exist comparing the algorithms using the same laser platform in both eyes for PRK surgery. In this prospective, randomized, eye-to-eye study, we compared the WaveLight Allegretto WFG and WFO ablation profiles in contralateral eyes with myopia with or without astigmatism. It should be noted that the WFG profile did not compensate for the introduction of spherical aberration. This study shares similar background and methods with a prior study undertaken by our group comparing WFG versus WFO algorithms using the same laser platform in patients undergoing LASIK.15

Patients and Methods

A total of 42 eyes of 21 participants with myopia with or without astigmatism were randomized to receive either WFG or WFO PRK with the WaveLight Allegretto Eye-Q 400-Hz excimer laser platform in this pilot study to compare WFG and WFO PRK. The primary outcome measurement was to detect a difference in uncorrected distance visual acuity (UDVA) at 12 months postoperatively. A power calculation was performed and determined that we needed a minimum of 18 patients to detect a significant difference between the two treatment modalities. Randomization was performed according to a computer-generated randomization schedule that assigned the dominant eye to receive WFG or WFO PRK and the fellow eye to receive the alternative procedure. A contralateral model was selected as the best to detect differences. Participants were masked as to which eye received which treatment, but the examiners were not. Inclusion criteria were corrected distance visual acuity (CDVA) of 20/20 or better, age older than 21 years, a stable refraction with a change of less than 0.50 diopters (D) of sphere or cylinder in the past year, discontinuation of soft contact lens wear at least 7 days before preoperative evaluation, and the ability to participate in follow-up examinations for at least 12 months after refractive surgery.

Exclusion criteria included significant dry eye or blepharitis, use of rigid gas permeable contact lenses, and corneal pathology (ie, basement membrane disease, recurrent erosion syndromes, irregular corneal mires on central keratometry, or keratoconus). Also excluded were patients with a baseline standard manifest refraction with a difference of 0.75 D in sphere power or 0.50 D in cylinder power compared with the baseline standard cycloplegic refraction; history of herpes zoster or herpes simplex; corneal warpage and corneal pachymetry in which the PRK procedure would result in less than 250 µm of the remaining posterior corneal thickness; and certain systemic diseases or conditions (ie, connective tissue disease, diabetes, pregnancy, lactation, immunocompromised state, and severe atopy). Also excluded were patients with sensitivity to the study's concomitant medications and patients participating in a clinical trial for another ophthalmic drug or device. Each participant signed an informed consent form approved by the Stanford University Institutional Review Board before enrollment.

Patients who met the preceding criteria underwent a comprehensive preoperative evaluation. This included a complete history, examination with slit-lamp biomicroscopy, Goldmann applanation tonometry, measurement of CDVA under controlled ambient conditions with 5% and 25% contrast acuity (Precision Vision, La Salle, IL), infrared pupillometry (Neuroptics, Irvine, CA) under photopic and scotopic lighting conditions, dilated fundus examination, manifest and cycloplegic refraction using Early Treatment Diabetic Retinopathy Study (ETDRS) charts, computerized corneal topography, and wavefront aberrometry using both the VISX WaveScan WaveFront (Abbott Medical Optics, Santa Ana, CA) and the Alcon WaveLight Allegro Analyzer (Alcon Laboratories, Inc.).

Patients then completed a previously validated questionnaire. The questionnaire chosen for this study has been used and validated in previous contralateral eye studies detailing symptoms, which included quantitative grading on a scale of 0 (no symptoms) to 10 (severe symptoms) for each of the following parameters: glare under night and day conditions, haze, halos, clarity under night and day conditions, dry eye symptom frequency and severity, gritty or scratchy sensation, vision fluctuation, and ghosting.16–18 Patients were also asked to grade their overall vision on a scale of 0 (poor vision) to 10 (excellent vision), as well as whether they preferred one eye over the other eye (Table A, available in the online version of this article). The questionnaire was administered preoperatively and postoperatively at months 1, 3, 6, and 12.

Postoperative Characteristics of Eyes Undergoing WFG and WFO TreatmentsPostoperative Characteristics of Eyes Undergoing WFG and WFO Treatments

Table A:

Postoperative Characteristics of Eyes Undergoing WFG and WFO Treatments

Wavefront aberrations were measured preoperatively with a physiologic pupil under controlled scotopic conditions with the WaveLight Allegro Analyzer aberrometer and the WaveScan aberrometer. The WaveLight Allegro Analyzer was used to plan WFG treatments. All eyes were imaged postoperatively with the WaveScan aberrometer. Although luminance was not measured, all aberrometry measurements were performed in the same room under standardized lighting conditions. To account for the potential variability caused by measuring HOAs at different pupil diameters, aberrometry measurements that were taken when the pupil was within 0.25 mm of the preoperative diameter were used for data analysis. All scans of all eyes had a pupil diameter of greater than 5 mm. All data were normalized to a 5-mm pupil using the WaveScan aberrometer Zernicke tool. Six readings from each eye were taken at each visit before and after surgery when possible, and the best acquisition was used for analysis as determined by the clearest centroid image. Tscherning aberrometry was also performed preoperatively, but not at postoperative visits.

All PRK surgeries were performed by the same surgeon (EEM) at one facility (Stanford University Eye Laser Center), and both procedures were performed during the same visit. Each eye was pretreated with proparacaine hydrochloride 0.5%, moxifloxacin hydrochloride ophthalmic solution 0.5%, and ketorolac tromethamine ophthalmic solution 0.4% before the procedure. The epithelium was removed using an Amoils epithelial scrubber (Innovative Excimer Solutions, Inc., Toronto, Canada) over a 9-mm zone centered over the pupil. Photoablation was performed using the WaveLight Allegretto Eye-Q 400-Hz excimer laser with autocentration and autotracking. Topical mitomycin C 0.02% was then applied for 12 seconds in every eye. A bandage contact lens was placed for healing, and patients were instructed to use topical moxifloxacin 0.5% four times a day until the epithelium was healed and fluorometholone ophthalmic solution 0.1% four times a day for 2 weeks and then two times a day for 2 weeks.

Patients were evaluated at postoperative day 1, week 1, and months 1, 3, 6, and 12. The primary efficacy end point was the difference in UDVA at month 12. Secondary outcome measures were comparisons of CDVA, 5% and 25% contrast CDVA, and HOAs at the 12-month follow-up visit. Self-reported quality of vision data were also compared across postoperative visits. No changes were made to the treatment or outcome analysis protocol after initiation of the trial. Secondary outcome measures were similarly compared using the paired t test, signed-rank test, or McNemar test for paired binomial variables under the assumption that the right and left eyes were symmetric. Based on a Bonferroni correction, two-sided P values less than .007 were considered statistically significant for secondary outcome measures.

Results

One participant had surgery performed but was lost to follow-up and thus excluded from data analysis. Of those with follow-up, 10 participants comprising 20 of the 40 eyes enrolled were men (50%). The mean age of the cohort was 34 ± 10.17 years (range: 25 to 56 years). All eyes were myopic with or without astigmatism. The computer-generated schedule resulted in 10 distance-dominant eyes randomized to the WFG group and 10 randomized to the WFO group. Preoperative astigmatism ranged from 0.00 to 2.75 D and sphere ranged from 0.00 to −8.00 D. At baseline, there were no statistically significant differences between the WFG and WFO groups for all studied parameters, including UDVA, contrast sensitivity, refractive error, HOAs (all P > .05), and quality of vision parameters.

Efficacy and Safety

Figures 12 show the postoperative visual and refractive outcomes and a summary is provided in Table A. There were no statistically significant differences in mean UDVA and CDVA between the WFG and WFO groups at all postoperative months (all P > .05). The frequencies of achieving postoperative UDVA of 20/16 or better, 20/20 or better, 20/30 or better, 20/40 or better, or 20/50 or better were not statistically different between the groups (all P > .05). Moreover, the frequencies with which the groups maintained their preoperative CDVA, lost one or two or more lines, or gained one or two or more lines after undergoing PRK were not statistically different from each other either (all P > .05). There was also no difference in astigmatism in the WFG group compared to the WFO group across all follow-up visits, with no significant differences indicating one group reached stability faster than the other (P > .05).

Wavefront-guided (WFG) standard refractive graphs. UDVA = uncorrected distance visual acuity; CDVA = corrected distance visual acuity; D = diopters; SEQ = spherical equivalent; SD = standard deviation; TIA = target induced astigmatism; SIA = surgically induced astigmatism

Figure 1.

Wavefront-guided (WFG) standard refractive graphs. UDVA = uncorrected distance visual acuity; CDVA = corrected distance visual acuity; D = diopters; SEQ = spherical equivalent; SD = standard deviation; TIA = target induced astigmatism; SIA = surgically induced astigmatism

Wavefront-optimized (WFO) standard refractive graphs. UDVA = uncorrected distance visual acuity; CDVA = corrected distance visual acuity; D = diopters; SEQ = spherical equivalent; SD = standard deviation; TIA = target induced astigmatism; SIA = surgically induced astigmatism

Figure 2.

Wavefront-optimized (WFO) standard refractive graphs. UDVA = uncorrected distance visual acuity; CDVA = corrected distance visual acuity; D = diopters; SEQ = spherical equivalent; SD = standard deviation; TIA = target induced astigmatism; SIA = surgically induced astigmatism

Table 1 compares 12-month HOA measurements with those made preoperatively. Both groups had improvements in UDVA and CDVA along with sphere, cylinder, and spherical equivalents (P < .05). Comparing the changes in HOAs from baseline between groups, there was a significant improvement in root mean square (RMS) error and astigmatism (P < .05), whereas all other HOA measurements saw no statistical change.

Comparison of Preoperative and 12-Month Postoperative HOAs

Table 1:

Comparison of Preoperative and 12-Month Postoperative HOAs

Low Contrast Visual Acuity

No statistically significant difference was found in mean CDVA between the groups at all postoperative time intervals studied for less than 5% and less than 25% contrast visual acuity conditions (all P > .05).

HOAs

There were no statistically significant differences in coma, trefoil, and higher order root RMS error between the groups postoperatively (all P > .05).

Subjective Parameters

There were no statistically significant differences in subjective parameters between the groups preoperatively or at 1 year postoperatively (all P > .05) (Table 2). However, among the WFG subset, there was an improvement at 1 year postoperatively compared to pretreatment symptoms in subjective glare bothersomeness (P = .04), halo bothersomeness (P = .04), blurred vision bothersomeness (P = .04), focusing difficulty frequency (P = .01), severity (P = .04), and bothersomeness (P = .01), and difficulty judging distance or depth frequency (P = .02) and severity (P = .04). The WFO subset saw an improvement at 1 year postoperatively compared to pretreatment symptoms in subjective halo bothersomeness (P = .04), blurred vision bothersomeness (P = .04), focusing difficulty frequency (P = .03), and focusing difficulties bothersomeness (P = .01). These differences trended toward significance but not at a P value of less than .007 with Bonferroni correction.

Preoperative and 12-Month Postoperative Quality of Vision

Table 2:

Preoperative and 12-Month Postoperative Quality of Vision

Participants more frequently preferred their WFO eye (25%) than their WFG eye (15%), but this trend did not reach statistical significance either (P > .05) (Table 2). More eyes changed in preference from WFG to WFO (3 patients) than from WFO to WFG (0 patients).

Discussion

In this prospective study, we randomly selected 1 eye from each of 40 participants to compare the outcomes of the WFG and WFO PRK platforms of the Alcon WaveLight Allegretto Eye-Q 400-Hz excimer laser system in the treatment of myopia with or without astigmatism at 1, 3, 6, and 12 months. Past studies have shown that although conventional ablation profiles are able to greatly improve patients' UDVA, they also have been shown to induce a significant increase in HOAs. WFG and WFO treatments have been developed with the goal of providing optimal optical quality by reducing some component of the existing or induced optical aberrations. These profiles require large-scale, randomized, prospective trials to determine the optimal treatment for patients. The visual significance of the increase in HOAs after excimer corneal ablations is still unclear. Increases in HOAs have the potential to degrade image quality by creating distortions, such as halos, haze, and starbursts that may manifest in low-contrast situations.13

Several investigations have compared outcomes after WFO and WFG treatment profiles in LASIK. Some studies have shown no difference between the two profiles. However, others suggested improved outcomes with WFG treatment. Few studies have investigated WFO and WFG treatment profiles in PRK. All have showed no difference between the profiles.4,19,20

Our study addresses limitations from prior studies by using the same laser platform to perform WFO and WFG PRK. This study randomized contralateral eyes to WFG and WFO platforms because fellow eyes in the same individual are generally accepted to have more similar wound healing and corneal biomechanical properties than pairs of eyes from different individuals. Our results are less likely to be confounded by these factors and therefore more likely to be accurate. We were unable to eliminate cross-talk between eyes, which may be a possible influence.

Our results confirm that PRK surgery using both WFG and WFO ablations profiles are effective, predictable, and safe for the treatment of myopia with or without astigmatism. At 12 months, 95% of eyes undergoing WFG and 100% of eyes undergoing WFO achieved 20/25 or better visual acuity, with 80% of WFG eyes and 85% of WFO eyes achieving 20/20 or better visual acuity, and there were no statistically significant differences between the group's mean CDVA under less than 5% and less than 25% contrast sensitivity conditions (all P > .05). At 12 months postoperatively, there was also no statistically significant difference between the groups' frequencies of achieving refractive errors within ±0.50 D of emmetropia and losing one or more lines of visual acuity on an Early Treatment Diabetic Retinopathy Study chart (all P > .05). However, one must consider the alternative hypothesis that there was insufficient power to detect differences between the groups that are of clinical importance.

Additionally, our results did not show any statistically significant difference in the induction of HOAs between WFG and WFO ablation patterns. There were no statistically significant differences in coma, trefoil, and higher order RMS error between the groups postoperatively (all P > .05).

As noted above, most published studies have shown similar outcomes between WFG and WFO treatments, with some studies showing a slight benefit with WFG treatment. Possible explanations for similar outcomes in both of our groups include low level of HOAs in our population cohort, lack of efficacy of the WFG treatment with regard to HOAs, superb performance of the WFO ablation, or small sample size. It is also possible that wound healing reactions in the epithelium after PRK may influence the effect of the aberration correction. Because there were few induced HOAs in either group in our study, this would indicate excellent performance of both ablation profiles or a wound healing effect. Our small sample size may also have been a limiting factor, and a much larger study would be needed to confirm our findings.

Some studies have suggested that the best measure is the actual subjective perception of quality of vision because this underlies patient satisfaction with the surgery. Bühren et al.20 showed that there is a high correlation between patient-perceived overall quality of vision and the experience of symptoms such as glare, halos, and starbursts but not wavefront data or contrast sensitivity measures. Because patient satisfaction is high in general after refractive surgery, with satisfaction rates for LASIK reported between 95% and 100%, it may be difficult to distinguish subtle differences between treatment profiles. In this study, we found no statistically significant differences in subjective parameters between study groups at 12 months postoperatively. Although subgroup analysis showed an improvement in subjective visual symptoms within each group, these should be treated as trends given the small sample size and secondary outcome nature of the data. However, these trends highlight the overall satisfaction with visual outcomes after refractive surgery with both platforms.

For this study, a previously validated Rasch model was chosen. One may also consider the important points raised by McNeely et al.21 in their discussion of an alternative application of Rasch analysis in its application to ophthalmic questionnaires.

Although aberrometry measurements for WFG treatments were collected for all patients enrolled in the study, it is a labor-intensive process that may be challenging for many practices to replicate. Perez-Straziota et al.9 reported that 14 of 66 eyes (21%) were scheduled for but unable to complete WFG treatment because of alignment or inconsistencies with their manifest refraction. Physicians may prefer to use WFO treatments if they have overall equivalent outcomes to WFG treatments because WFO can be more easily performed without the need to obtain and analyze aberrometry data.

WFG ablations were performed in eyes with all levels of preoperative HOAs in our study. The manufacturer of the Allegretto excimer laser (Alcon Laboratories, Inc.) advises using WFO treatment for most cases and considering using WFG treatment for eyes with preoperative HOAs greater than 0.35 um.22 We may have been able to demonstrate the superiority of WFG over WFO ablations if we had followed this selection criterion.

Recent studies have looked at clinical outcomes using the combination of WFG ablation with an optimized aspheric ablation and compared them with the outcomes of WFG ablations alone.23,24 Those studies found that the combined optimized aspheric and WFG ablations produced significantly better clinical outcomes compared with WFG ablations alone. This combination of WFO and WFG ablation profiles may ultimately prove to be superior to either technique independently; however, the profile is not currently available on the excimer laser platform evaluated in this trial. In addition, recent studies by Schumacher et al.25 and Cummings and Kelly26 reported clinical outcomes using a novel ray-tracing aberrometer to drive WFG treatments compared with Tscherning aberrometer–driven WFG, WFO, and topography-guided LASIK using the Allegretto excimer laser. Cummings and Kelly26 demonstrated that ray-tracing aberrometry–driven WFG produced clinical outcomes superior to those of WFO, topography-guided, and Tscherning aberrometry–driven WFG LASIK treatments. Their study concluded there is an advantage of WFG over WFO and suggested that ray-tracing–driven WFG ablations can yield improved outcomes over our current WFG technology. This study was performed on the same Allegretto platform used in the current study. However, that ray-tracing driven–WFG technology is not approved by the U.S. Food and Drug Administration and is not commercially available in the United States.

Although this study addressed limitations from previous studies, it is still a relatively small sample size. This pilot study was intended to give us some indication as to whether one platform was superior to the other. Trends in laser platform preference and improvement of symptoms within each laser platform were identified, but a much larger sample size would be needed to reach statistical significance. A larger study could be done that would be powered sufficiently to validate the findings of this study.

Another limitation of our study was that we did not obtain postoperative wavefront measurements on the Allegro aberrometer. The Allegro aberrometer was used to generate the data to perform the WFG treatment. We acknowledge that it would have been more meaningful to have preoperative and postoperative measurements performed on the aberrometer that generated the data for the WFG treatment. Although we acknowledge this limitation, we still believe that the data obtained on the WaveScan aberrometer are valid because the measurements were performed preoperatively and postoperatively on the same device under the same conditions.

The findings of the current study suggest that the WFG and WFO approaches for PRK using the Alcon WaveLight Allegretto Eye-Q 400-Hz excimer laser platform in myopic eyes with or without astigmatism provide similar quantitative and qualitative results at 12 months postoperatively. It will be of interest whether the similarities between treatment groups in this cohort at 12 months remain stable or change with longer follow-up.

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Comparison of Preoperative and 12-Month Postoperative HOAs

ParameterPreoperative HOAs12-Month Postoperative HOAs


WFG MeanWFG CIWFO MeanWFO CIPWFG MeanWFG CIWFO MeanWFO CIP
Coma (µm)0.230.110.210.07.690.330.140.280.10.47
Trefoil (µm)0.130.040.180.09.130.150.070.150.061.00
RMS error (µm)0.360.070.380.09.640.470.120.470.10.92
Astigmatism (D)0.860.540.950.73.780.360.120.400.16.57

Preoperative and 12-Month Postoperative Quality of Vision

ParameterWFO Mean ± SDWFG Mean ± SDP
Preoperative
  Frequency of symptoms0.48 ± 0.260.46 ± 0.27.73
  Severity of symptoms0.43 ± 0.240.41 ± 0.26.70
  Bothersomeness of symptoms0.40 ± 0.220.39 ± 0.24.70
12-month postoperative
  Frequency of symptoms0.37 ± 0.240.31 ± 0.22.77
  Severity of symptoms0.36 ± 0.240.28 ± 0.20.71
  Bothersomeness of symptoms0.29 ± 0.240.22 ± 0.17.71

Postoperative Characteristics of Eyes Undergoing WFG and WFO Treatments

ParameterWFG Mean ± SDWFO Mean ± SDP
Preoperative
  logMAR UDVA (Snellen equivalent)1.36 ± 0.69 (20/500)1.28 ± 0.66 (20/400).71
  logMAR CDVA (Snellen equivalent)−0.07 ± 0.09 (20/15)−0.08 ± 0.09 (20/15).85
  logMAR 5% CDVA (Snellen equivalent)0.42 ± 0.16 (20/50)0.44 ± 0.14 (20/50).61
  logMAR 25% CDVA (Snellen equivalent)0.40 ± 0.13 (20/50)0.42 ± 0.10 (20/50).59
  Sphere (D)−4.61 ± 2.01−4.49 ± 2.00.84
  Cylinder (D)0.86 ± 0.970.84 ± 1.12.94
  Spherical equivalent (D)−4.18 ± 2.13−4.07 ± 2.15.87
  Coma (µm)0.23 ± 0.180.21 ± 0.11.69
  Trefoil (µm)0.13 ± 0.070.18 ± 0.14.13
  Spherical aberration (µm)0.15 ± 0.170.14 ± 0.19.83
  RMS error (µm)0.36 ± 0.120.38 ± 0.15.64
  Astigmatism (D)0.86 ± 0.880.95 ± 1.18.78
1-month postoperative
  logMAR UDVA (Snellen equivalent)0.11 ± 0.18 (20/25)0.04 ± 0.13 (20/20).19
  logMAR CDVA (Snellen equivalent)0.02 ± 0.16 (20/20)−0.03 ± 0.11 (20/20).24
  logMAR 5% CDVA (Snellen equivalent)0.45 ± 0.18 (20/63)0.50 ± 0.17 (20/63).41
  logMAR 25% CDVA (Snellen equivalent)0.46 ± 0.16 (20/63)0.48 ± 0.14 (20/63).68
  Sphere (D)−0.34 ± 0.45−0.28 ± 0.40.65
  Cylinder (D)0.36 ± 0.360.36 ± 0.391.00
  Spherical equivalent (D)−0.16 ± 0.43−0.09 ± 0.42.64
  Coma (µm)0.34 ± 0.200.31 ± 0.18.58
  Trefoil (µm)0.24 ± 0.190.27 ± 0.21.68
  Spherical aberration (µm)0.11 ± 0.200.13 ± 0.27.85
  RMS error (µm)0.59 ± 0.230.59 ± 0.24.95
  Astigmatism (D)0.42 ± 0.270.53 ± 0.37.32
3-month postoperative
  logMAR UDVA (Snellen equivalent)−0.05 ± 0.08 (20/15)−0.04 ± 0.13 (20/20).76
  logMAR CDVA (Snellen equivalent)−0.11 ± 0.09 (20/15)−0.10 ± 0.10 (20/15).73
  logMAR 5% CDVA (Snellen equivalent)0.38 ± 0.14 (20/50)0.40 ± 0.12 (20/50).61
  logMAR 25% CDVA (Snellen equivalent)0.38 ± 0.11 (20/50)0.39 ± 0.11 (20/50).76
  Sphere (D)−0.24 ± 0.32−0.18 ± 0.25.49
  Cylinder (D)0.28 ± 0.260.28 ± 0.231.00
  Spherical equivalent (D)−0.11 ± 0.32−0.05 ± 0.28.50
  Coma (µm)0.23 ± 0.150.20 ± 0.28.37
  Trefoil (µm)0.13 ± 0.100.17 ± 0.16.40
  Spherical aberration (µm)0.23 ± 0.190.21 ± 0.21.84
  RMS error (µm)0.44 ± 0.160.46 ± 0.18.64
  Astigmatism (D)0.39 ± 0.230.43 ± 0.25.59
6-month postoperative
  logMAR UDVA (Snellen equivalent)−0.08 ± 0.10 (20/15)−0.60 ± 0.10 (20/15).59
  logMAR CDVA (Snellen equivalent)−0.08 ± 0.09 (20/15)−0.60 ± 0.10 (20/15).58
  logMAR 5% CDVA (Snellen equivalent)0.40 ± 0.16 (20/50)0.37 ± 0.10 (20/50).58
  logMAR 25% CDVA (Snellen equivalent)0.37 ± 0.14 (20/50)0.39 ± 0.05 (20/50).73
  Sphere (D)−0.31 ± 0.28−0.33 ± 0.37.89
  Cylinder (D)0.14 ± 0.240.27 ± 0.28.19
  Spherical equivalent (D)−0.19 ± 0.24−0.16 ± 0.35.69
  Coma (µm)0.23 ± 0.180.23 ± 0.14.85
  Trefoil (µm)0.15 ± 0.100.15 ± 0.12.94
  Spherical aberration (µm)0.22 ± 0.190.18 ± 0.17.55
  RMS error (µm)0.43 ± 0.210.42 ± 0.18.86
  Astigmatism (D)0.38 ± 0.230.44 ± 0.29.56
12-month postoperative
  logMAR UDVA (Snellen equivalent)−0.05 ± 0.11 (20/15)−0.06 ± 0.09 (20/15).88
  logMAR CDVA (Snellen equivalent)−0.13 ± 0.07 (20/15)−0.11 ± 0.08 (20/15).40
  logMAR 5% CDVA (Snellen equivalent)0.47 ± 0.19 (20/63)0.47 ± 0.15 (20/63).93
  logMAR 25% CDVA (Snellen equivalent)0.39 ± 0.17 (20/50)0.38 ± 0.16 (20/50).77
  Sphere (D)−0.34 ± 0.30−0.31 ± 0.25.79
  Cylinder (D)0.25 ± 0.290.33 ± 0.30.43
  Spherical equivalent (D)−0.21 ± 0.27−0.15 ± 0.25.46
  Coma (µm)0.33 ± 0.230.28 ± 0.16.42
  Trefoil (µm)0.15 ± 0.120.15 ± 0.091.00
  Spherical aberration (µm)0.27 ± 0.230.21 ± 0.20.80
  RMS error (µm)0.47 ± 0.200.47 ± 0.16.92
  Astigmatism (D)0.36 ± 0.200.40 ± 0.26.57
Authors

From Byers Eye Institute, Stanford University School of Medicine, Palo Alto, California.

Dr. Manche has equity in Clarity Vision Technologies, RxSight, Inc., and VacuMed; is a consultant for Avedro, Carl Zeiss Meditec, J&J Vision, and Shire; and receives research support from Alcon, Allergan, Avedro, Presbia, and Carl Zeiss Meditec. Dr. Smith has no financial or proprietary interest in the materials presented herein.

AUTHOR CONTRIBUTIONS

Study concept and design (EEM); data collection (EEM); analysis and interpretation of data (EEM, RGS); writing the manuscript (RGS); critical revision of the manuscript (EEM, RGS); administrative, technical, or material support (EEM); supervision (EEM)

Correspondence: Edward E. Manche, MD, Byers Eye Institute, 2452 Watson Court, Palo Alto, CA 94303. E-mail: cornea@stanford.edu

Received: June 30, 2019
Accepted: January 15, 2020

10.3928/1081597X-20200129-01

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