Contralateral eyes were randomized to receive either wavefront-guided (WFG) or wavefront-optimized (WFO) photorefractive keratectomy and were monitored for 1 year after the operation.
A, Uncorrected distance visual acuity (UDVA). B, Change in corrected distance visual acuity (CDVA). No eyes lost 2 lines or more. C, Spherical equivalent attempted vs achieved: y = 0.96x + 0.01; R2 = 0.99. Mean (SD), −4.66 (2.29) diopters (D); range, 0.63 to −10.75 D. D, Spherical equivalent refractive accuracy: ±0.50 D, 87%; and ±1.00 D, 97%. E, Refractive astigmatism: 0.50 D or less, 93%; and 1.00 D or less, 100%. F, Stability of spherical equivalent refraction: 10% changed more than 0.50 D from 3 to 12 months. Circles indicate mean values; limit lines, SD.
A, Uncorrected distance visual acuity (UDVA). B, Change in corrected distance visual acuity (CDVA). No eyes lost 2 lines or more. C, Spherical equivalent attempted vs achieved: y = 0.98x + 0.04; R2 = 0.99. Mean (SD), −4.55 (2.31) diopters (D); range, 0.50 to −11.00 D. D, Spherical equivalent refractive accuracy: ±0.50 D, 89%; and ±1.00 D, 99%. E, Refractive astigmatism: 0.50 D or less, 93%; and 1.00 D or less, 100%. F, Stability of spherical equivalent refraction: 15% changed more than 0.50 D from 3 to 12 months. Circles indicate mean values; limit lines, SD.
eTable. Preoperative characteristics of eyes undergoing wavefront-guided (WFG) and wavefront-optimized (WFO) treatments
He L, Manche EE. Contralateral Eye-to-Eye Comparison of Wavefront-Guided and Wavefront-Optimized Photorefractive KeratectomyA Randomized Clinical Trial. JAMA Ophthalmol. 2015;133(1):51-59. doi:10.1001/jamaophthalmol.2014.3876
Copyright 2015 American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use.
Wavefront-guided (WFG) and wavefront-optimized (WFO) platforms for refractive surgery are designed for improved visual outcomes. It is unclear which treatment profile is superior for patients undergoing photorefractive keratectomy (PRK).
To compare the safety, efficacy, predictability, stability, and higher-order aberrations in eyes undergoing WFG and WFO PRK.
Design, Setting, and Participants
A prospective, randomized, fellow-eye–controlled clinical trial was conducted at the Byers Eye Institute at Stanford with enrollment between April 2009 and March 2011; 1 year of follow-up was included. Of 90 patients screened, 71 patients (142 eyes) with less than 12.00 diopters (D) of spherical myopia and less than 3.00 D of astigmatism were enrolled consecutively.
One eye was randomized to undergo WFG PRK treatment (Visx CustomVue Star S4 IR excimer laser system; Abbott Medical Optics), and the fellow eye received WFO PRK treatment (WaveLight Allegretto Wave Eye-Q 400 Hz excimer laser system; Alcon Surgical).
Main Outcomes and Measures
Data on the manifest refraction, uncorrected visual acuity, best-corrected visual acuity, 5% and 25% contrast best-corrected visual acuity, and higher-order aberrations were collected preoperatively and at the 1-, 3-, 6-, and 12-month follow-up visits.
Eyes undergoing both treatments had improved best-corrected visual acuity (WFG: mean, 0.05 [95% CI, 0.03-0.07]; WFO: mean, 0.04 [95% CI, 0.02-0.06]) and less sphere (WFG: mean, −4.79 [95% CI, −5.31 to −4.26]; WFO: mean, −4.61 [95% CI, −5.18 to −4.03]), cylinder (WFG: mean, 0.66 [95% CI, 0.49-0.82]; WFO: mean, 0.52 [95% CI, 0.35-0.69]), and spherical equivalents (WFG: mean, −4.45 [95% CI, −4.99 to −3.91]; WFO: mean, −4.34 [95% CI, −4.92 to −3.76]) (P < .001) but higher levels of spherical aberration (WFG: mean, −0.11 [95% CI, −0.15 to −0.06]; WFO: mean, −0.11 [95% CI, −0.14 to −0.07]) (P < .001) and higher-order root-mean-square aberrations (WFG: mean, −0.07 [95% CI, −0.12 to −0.02]; WFO: mean, −0.12 [95% CI, −0.17 to −0.07]) (P = .005 in WFG eyes and P < .001 in WFO eyes) at 12 months compared with preoperative measurements. A total of 93.0% of the eyes in the WFG group and 94.4% in the WFO had an uncorrected visual acuity of 20/20 or better at 12 months, with 56.3% in the WFG group and 43.7% in the WFO group gaining 1 or more lines of best-corrected visual acuity. The stability of the refractive correction was excellent for both groups.
Conclusions and Relevance
A difference in uncorrected visual acuity or contrast acuity between eyes undergoing WFG or WFO treatment at 3 months and beyond could not be identified. This lack of difference suggests that both systems can be used to provide excellent improvement in vision for persons with myopia.
clinicaltrials.gov Identifier: NCT01135719
Surgeons performing refractive procedures are constantly seeking improved postoperative visual outcomes and quality of vision. Recent focus has been on treatment profiles that not only address lower-order aberrations, such as sphere and cylinder, but can also correct for higher-order aberrations, such as spherical aberration, coma, and trefoil.1,2 These aberrations are thought to be responsible, at least in part, for glare, halos, haze, and starbursts, which can degrade image quality.1,3- 5 Wavefront-optimized (WFO) laser ablation profiles are designed to deliver additional treatment to the peripheral cornea in an attempt to preserve the naturally prolate shape of the cornea and minimize induction of higher-order aberrations while preserving the preexisting aberrations of the eye.3 Wavefront-guided (WFG) treatments require preoperative measurement of the eye’s aberrations using a wavefront aberrometer and attempt to correct both lower- and higher-order aberrations.3
There have been a few published studies6- 13 comparing WFG treatments with WFO treatments in patients undergoing laser in situ keratomileusis (LASIK) but only one other published study directly comparing the effects of these treatments on patients undergoing photorefractive keratectomy (PRK). Moshirfar et al14 monitored 23 patients for 3 months and found no difference in the visual acuity or refractive error outcomes between patients undergoing treatment with either system. With a limited number of patients and short length of follow-up, it is still unclear whether one of the profiles is more successful at achieving the goal of optimal vision. The LASIK data are also inconclusive, with some reports6- 9 showing an improvement in quality of vision after WFG treatment but many others10- 12 showing no difference between the 2 profiles.
This present study prospectively compared WFG and WFO treatment profiles in eyes undergoing PRK to evaluate their effect on refractive correction, contrast sensitivity, and higher-order aberrations and to determine whether one treatment profile leads to more optimal vision than the other.
The institutional review board at the Stanford University School of Medicine approved this clinical trial. Participants provided written informed consent; they did not receive financial compensation. A total of 142 eyes of 71 patients were enrolled from the refractive surgery service from April 1, 2009, to March 31, 2011, and monitored for 1 year (Figure 1). Power calculations showed that 40 patients were necessary to detect a visual acuity difference between treatment profiles.
The inclusion criteria of the study were less than 12.00 diopters (D) of myopia with less than 3.00 D of refractive astigmatism, stable refraction with less than a 0.50-D change in sphere and cylinder the prior year, best-corrected visual acuity (BCVA) of 20/20 or better in both eyes, cessation of soft contact lens use for 7 or more days before the preoperative visit, and age 21 years or older. Exclusion criteria were severe ocular surface disease; use of rigid gas-permeable contact lens; corneal disease; cataracts; baseline difference of greater than 0.75 D in sphere power or greater than 0.5 D in cylinder power between standard manifest and cycloplegic refractions; previous intraocular or corneal surgery; a history of herpetic keratitis; current use of systemic immunosuppressive therapy; presence of clinically significant atopic disease, connective tissue disease, or diabetes mellitus; a history of elevated eye pressure in response to corticosteroids; a history of glaucoma; a preoperative intraocular pressure of 21 mm Hg or greater; macular disease; pregnancy or lactation; sensitivity to study medications; and current participation in another ophthalmic drug or device clinical trial.
The patients’ dominant eye was determined by the Dolman method.15- 17 Participants were randomized using a computer-generated schedule to undergo WFG PRK (Visx CustomVue Star S4 IR excimer laser system; Abbott Medical Optics) or WFO PRK (WaveLight Allegretto Wave Eye-Q 400 Hz excimer laser system; Alcon Surgical). A study technician put the randomization information into an envelope, which the surgeon opened on the day of the operation, keeping patients masked to the treatment received. The ophthalmologist was not masked on the day of treatment.
The Visx CustomVue Star S4 IR excimer laser system uses variable spot-scanning technology (beam sizes, 0.65-6.5 mm) and a variable repetition rate (6-20 Hz). Iris registration accounts for any cyclorotational misalignment or centroid shift, and a 60-Hz active infrared eye tracking system compensates for additional movement. The standard default optical treatment zone is 6.0 mm with an 8-mm transition blend zone.
The WaveLight Allegretto Wave Eye-Q 400 Hz excimer laser system uses a fixed 0.95-μm scanning spot with a 400-Hz repetition rate and a 200-Hz active infrared eye tracking that compensates for eye movements. The standard default optical treatment zone is 6.5 mm with an 8-mm transition blend zone.
Each patient received a comprehensive preoperative examination with history and slitlamp biomicroscopy examination, Goldmann applanation tonometry, infrared pupilometry (Neuroptics) under photopic and scotopic conditions, manifest refraction with Early Treatment of Diabetic Retinopathy Study charts, 5% and 25% contrast sensitivity best-corrected visual acuity (Precision Vision), computerized corneal topography using the Pentacam (Oculus Optikgeräte GmbH) higher-order aberration analysis (Visx WaveScan aberrometer; Advanced Medical Optics, Inc) measured with an undilated pupil. A similar examination was performed at each subsequent follow-up visit. Wavefront analysis was performed under mesopic conditions with images within 0.25 mm of the preoperative measurement. Six readings were taken, and the clearest centroid image was selected.
One surgeon (E.E.M.) performed all of the PRK surgeries as described in previous studies.18 An epithelial scrubber (Amoils; Innovative Excimer Solutions, Inc) was used to remove the epithelium over an 8.0-mm zone centered over the pupil, and ablation using autocentration and iris recognition was targeted for full correction. No adjunct mitomycin C was used for any of the cases. A bandage contact lens (Acuvue Oasys; Johnson & Johnson Vision Care, Inc) and topical moxifloxacin hydrochloride, 0.5% (Alcon), administered 4 times daily were used until the epithelium healed. Patients also received topical fluorometholone, 0.1% (Allergan), 4 times daily for 2 weeks and then twice daily 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 uncorrected visual acuity (UCVA) at month 12. Secondary outcome measures were comparisons of BCVA, 5% and 25% contrast BCVA, and higher-order aberrations at the 12-month follow-up visits. No changes were made to the treatment or outcome analysis protocol after initiation of the trial. Statistical analysis was performed using SPSS software, version 20/0 (SPSS Inc). A paired, 2-tailed t test was used to compare the logMAR visual acuities and aberrations between the eyes at each time point studied.
A total of 142 eyes of 71 patients were enrolled in this study starting April 2009, with follow-up terminating in March 2012 when the enrollment was satisfactory for analysis. The median age was 36 years (range, 23-61 years); 24 patients were male and 47 were female. All eyes enrolled were myopic with or without astigmatism. Figure 1 shows the progression of enrollment. The preoperative characteristics of the eyes randomized to each type of treatment are displayed in the eTable in the Supplement. The eyes were mostly similar in their lower- and higher-order aberrations. The WFG eyes had more sphere and cylinder error (P = .04 and P = .01, respectively), but the groups had no significant difference in spherical equivalent error (P = .16).
A summary of the postoperative outcomes is provided in Table 1. In the first postoperative month, patients had better UCVA, BCVA, and 5% and 25% contrast BCVA in their WFO eye (P = .04, P = .02, P = .006, and P = .006, respectively). However, spherical aberration was less in the WFG eyes (P = .02). Improvement in visual acuity and contrast acuity in the WFO eyes was no longer detected at 3 months and later. Also at 3 months and later, eyes undergoing WFO treatment had higher levels of coma, trefoil, and higher-order root-mean-square aberrations (HOAs).
Table 2 compares 12-month acuity and aberration measurements with those made preoperatively. Both groups had improvements in UCVA and BCVA along with sphere, cylinder, spherical, and equivalent refractive error (P < .01). HOAs and spherical aberrations increased (P < .01) for both groups. Comparing the change in HOAs from baseline between groups, there was significantly more increased coma in the WFO-treated eyes compared with the WFG eyes (mean increase, 0.022 in the WFG eyes and 0.093 in the WFO eyes; P = .006). Changes in other types of HOAs, such as trefoil, spherical aberration, and overall, were not significantly different between the 2 groups (P = .10, P = .96, and P = .09, respectively), but there were greater increases in all 3 measures in the WFO-treated eyes (WFG eyes decreased by −0.021 from baseline, and WFO eyes increased by 0.007 for trefoil; WFG eyes increased by 0.106, and WFO eyes increased by 0.107 for spherical aberration; and WFG eyes increased by 0.072, and WFO eyes increased by 0.118 for overall HOAs).
Measures for efficacy, safety, accuracy, predictability, astigmatism, and stability 12 months after treatment are summarized in Figure 2 for the WFG eyes and Figure 3 for the WFO eyes. A total of 94.4% (67) of the WFO eyes achieved 20/20 UCVA or better, with 54.9% (39) achieving 20/12.5, and 28.2% (20) achieving 20/16. Similarly, 93.0% (66) of the WFG eyes achieved 20/20 UCVA or better. However, 62.0% (44) were 20/12.5 or better, and 26.8% (19) had 20/16 visual acuity. In both groups, 7 eyes (9.9%) lost 1 line of BCVA, but all were correctable to 20/20 or better. More eyes receiving WFG treatment gained 1 line of vision or more (56.3% [40 eyes]) compared with the WFO group (43.7% [31 eyes]). There was no significant difference between the groups when the safety outcomes were compared (P = .34). No complications occurred in any of the eyes.
In the WFO group, only 4 of the eyes (5.6%) achieved worse than 20/20 UCVA. In the WFG group, only 5 eyes (7.0%) had UCVA worse than 20/20. Both treatments were effective at reducing refractive astigmatism, with all eyes achieving 0.75 D or less. The stability of spherical equivalent refraction was also similar between the 2 groups, with a mean closest to plano at 3 months (−0.14 D in the WFG eyes and −0.04 in the WFO eyes) but then slowly decreasing at 6 and 12 months (−0.19 and −0.21 D for the WFG eyes and −0.10 and −0.20 D for WFO eyes, respectively).
Conventional ablation profiles are able to greatly improve patients’ UCVA but have been known to induce a significant increase in HOAs.19,20 Additional excimer ablation profiles, such as WFG and WFO, have been developed with the goal of providing optimal optical quality by reducing some component of the existing or induced optical aberrations.21- 26 These profiles require large-scale, randomized, prospective trials to determine the optimal treatment for patients.
Several investigations have compared outcomes after WFO and WFG treatment profiles in LASIK.6,7,9- 13,27 Some studies10- 12 have shown no difference between the 2 profiles. However, others6,7,9 suggested improved outcomes with WFG treatment. The only other study14 comparing use of WFO and WFG platforms in PRK showed no difference between the profiles. To our knowledge, the present study is the largest investigation with the longest follow-up designed to compare these 2 profiles in PRK and determine whether one delivers high-quality vision more effectively than the other.
The results of the present study could not identify a difference in visual acuity outcomes in eyes receiving WFG or WFO treatment for refractive correction more than 3 months postoperatively. The WFO eyes had better visual acuity and contrast acuity in the first postoperative month. Both treatments demonstrated good efficacy, safety, and predictability profiles while the patients were monitored during the first postoperative year. This outcome is in line with previous studies that have shown the safety and efficacy of WFG18,28 and WFO29,30 PRK without a direct comparison of the procedures. There was a higher proportion (62.0%) of eyes undergoing WFG treatment that achieved a UCVA of 20/12.5 compared with those in the WFO group (54.9%). This trend was also seen in the 3-month investigation by Moshirfar et al14 of 23 patients. In addition, there were more eyes in the WFG group (56.3%) that gained lines of BCVA compared with those in the WFO group (43.7%). The same number (9.9%) of eyes lost 1 line of BCVA in both treatment groups, but all remained correctable to 20/20 or better.
There were several differences found between the profiles. Patients experienced better visual acuity and contrast acuity from their WFO eyes at 1 month but not at 3 months and later. Eyes receiving WFG treatment consistently had fewer HOAs of trefoil and coma at 3 months and later but not initially during the first postoperative month. This outcome is not surprising given that the treatment targets HOAs.3,21 The total HOAs and spherical aberrations were higher after treatment when compared with baseline in both groups, but coma was higher compared with baseline only in the WFO eyes (P < .001). Karimian et al1 showed that HOA values increased after both conventional and WFG PRK, with a greater increase induced in eyes undergoing WFG because of a small ablation zone. Nassiri et al30 compared contrast sensitivity after conventional and WFO PRK and showed that both decreased sensitivity at 3 months, but there was better preservation at lower spatial frequencies in the WFO group.
The visual significance of the increase in HOAs after excimer corneal ablations is still unclear. Increases in higher-order aberrations have the potential to degrade image quality by creating distortions, such as halos, haze, and starbursts, that may manifest in low-contrast situations.1,3- 5,31- 35 However, the eyes in the present study did not experience any changes in 5% or 25% contrast sensitivity between either treatment type or when compared with baseline. The total level of HOAs was very low before and after the treatment, increasing from a mean of 0.35 and 0.38 μm preoperatively to 0.42 and 0.50 μm 1 year postoperatively in the WFG and WFO eyes, respectively. The absolute level of aberration may still be negligible even though there was an increase (P < .006). It remains to be determined whether the overall increases in HOAs ultimately affect patients’ perceived quality of vision.
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 al36 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 very high in general after refractive surgery, with satisfaction rates for LASIK reported between 95% and 100%,27,37,38 it may be difficult to distinguish subtle differences between treatment profiles.
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 al11 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. It has been suggested12,39 that WFG LASIK may benefit patients who have larger levels of higher-order aberrations. The present study had a population of patients among whom 55% had HOAs of greater than 0.3 μm but still showed overall equivalent results in visual acuity between the 2 groups.
Recent studies40,41 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. 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 either of the excimer laser platforms evaluated in this trial. In addition, recent studies by Schumacher et al42 and Cummings and Kelly43 reported on 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 Kelly43 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 confirms the advantage of WFG over WFO and suggests that ray-tracing–driven WFG ablations can yield improved outcomes over our current WFG technology. This study43 was performed on the same Allegretto platform used in the present study. However, that ray-tracing driven–WFG technology is not approved by the US Food and Drug Administration and is not commercially available in the United States.
There were a number of limitations to our study, including the use of 2 different excimer laser platforms that use 2 different ablation patterns and optical treatment zone sizes. These differences alone might account for many of the observed variations in the outcomes that we noted. We are currently comparing WFG with WFO PRK on the Allegretto excimer laser alone to specifically address this issue. An additional limitation to our study is that we did not use adjunct mitomycin C in any of our treatments. However, since neither group received this agent, we do not believe that our results were affected.
Overall, the findings of the present study suggest that there were no differences identified in visual acuity outcomes in eyes undergoing WFG treatment compared with WFO profiles at 12 months, although there were initially better visual outcomes at 1 month in WFO eyes. There was also lower coma, trefoil, astigmatism, and HOA values for eyes that received WFG treatment. There was an increase in HOA values from preoperative levels in both groups. It may be that a larger enrollment will more definitively show equivalency or superiority of WFO compared with WFG.
Submitted for Publication: February 13, 2014; final revision received July 28, 2014; accepted July 31, 2014.
Corresponding Author: Edward E. Manche, MD, Byers Eye Institute at Stanford, 2452 Watson Ct, Stanford, CA 94303 (firstname.lastname@example.org).
Published Online: October 16, 2014. doi:10.1001/jamaophthalmol.2014.3876.
Author Contributions: Drs He and Manche had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: All authors.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: All authors.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: He.
Obtained funding: Manche.
Administrative, technical, or material support: Manche.
Study supervision: Manche.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr He reports receiving personal fees from Oculeve, Inc and from Auris Surgical Robotics. Dr Manche is a consultant for Gerson Lehrmann, Best Doctors, Inc, and Oculeve, Inc. He is a board member of and holds patents in Seros Medical, LLC. He is also an equity owner in Calhoun Vision, Inc, Veralas, Inc, Seros Medical, LLC, Kryton Vision, Inc, and Refresh Innovations, Inc.
Correction: This article was corrected on March 25, 2015, to fix the Abstract and Table 2.