Journal of Refractive Surgery

Original Article Supplemental Data

Contrast Sensitivity After Wavefront-Guided and Wavefront-Optimized PRK and LASIK for Myopia and Myopic Astigmatism

Denise S. Ryan, MS; Rose K. Sia, MD; Jeff Rabin, PhD; Bruce A. Rivers, MD; Richard D. Stutzman, MD; Joseph F. Pasternak, MD; Jennifer B. Eaddy, OD; Lorie A. Logan, OD; Kraig S. Bower, MD

Abstract

PURPOSE:

To compare contrast sensitivity among participants undergoing wavefront-guided or wavefront-optimized photorefractive keratectomy (PRK) or LASIK for the treatment of myopia or myopic astigmatism 12 months after surgery.

METHODS:

In a prospective, randomized clinical trial, 215 participants with myopia ranging from −0.50 to −7.25 diopters (D) and less than −3.50 D of manifest astigmatism electing to undergo either LASIK or PRK were randomized to receive wavefront-guided or wavefront-optimized treatment. Corrected Super Vision Test (Precision Vision, La Salle, IL) high contrast and small letter contrast sensitivity, uncorrected postoperative contrast sensitivity function, and uncorrected and corrected distance visual acuity were measured preoperatively and at 1, 3, 6, and 12 months postoperatively.

RESULTS:

There was a significant difference within each of the four groups over time when measuring high contrast visual acuity (P < .001) and small letter contrast sensitivity (P < .001), with the most significant decrease occurring 1 month postoperatively. However, there were no significant differences when comparing the four groups for high contrast sensitivity (P = .22) or small letter contrast sensitivity (P = .06). The area under the logarithm of contrast sensitivity function did not differ significantly over time (P = .09) or between groups (P = .16). A pairwise comparison of preoperative to 12-month CDVA showed a significant improvement in all groups (P < .017). The change in CDVA was also significantly different between groups as determined by one-way analysis of variance (P = .003).

CONCLUSIONS:

Wavefront-guided and wavefront-optimized PRK and LASIK procedures maintained high contrast, small letter contrast sensitivity, and contrast sensitivity function 12 months postoperatively. Although the recovery period for visual performance was longer for PRK versus LASIK, there was no significant difference in treatment type or treatment profile at 12 months postoperatively.

[J Refract Surg. 2018;34(9):590–596.]

Abstract

PURPOSE:

To compare contrast sensitivity among participants undergoing wavefront-guided or wavefront-optimized photorefractive keratectomy (PRK) or LASIK for the treatment of myopia or myopic astigmatism 12 months after surgery.

METHODS:

In a prospective, randomized clinical trial, 215 participants with myopia ranging from −0.50 to −7.25 diopters (D) and less than −3.50 D of manifest astigmatism electing to undergo either LASIK or PRK were randomized to receive wavefront-guided or wavefront-optimized treatment. Corrected Super Vision Test (Precision Vision, La Salle, IL) high contrast and small letter contrast sensitivity, uncorrected postoperative contrast sensitivity function, and uncorrected and corrected distance visual acuity were measured preoperatively and at 1, 3, 6, and 12 months postoperatively.

RESULTS:

There was a significant difference within each of the four groups over time when measuring high contrast visual acuity (P < .001) and small letter contrast sensitivity (P < .001), with the most significant decrease occurring 1 month postoperatively. However, there were no significant differences when comparing the four groups for high contrast sensitivity (P = .22) or small letter contrast sensitivity (P = .06). The area under the logarithm of contrast sensitivity function did not differ significantly over time (P = .09) or between groups (P = .16). A pairwise comparison of preoperative to 12-month CDVA showed a significant improvement in all groups (P < .017). The change in CDVA was also significantly different between groups as determined by one-way analysis of variance (P = .003).

CONCLUSIONS:

Wavefront-guided and wavefront-optimized PRK and LASIK procedures maintained high contrast, small letter contrast sensitivity, and contrast sensitivity function 12 months postoperatively. Although the recovery period for visual performance was longer for PRK versus LASIK, there was no significant difference in treatment type or treatment profile at 12 months postoperatively.

[J Refract Surg. 2018;34(9):590–596.]

Clinical vision testing usually focuses on visual acuity using high contrast black and white tests. However, testing vision with a range of optotypes of varying size and luminance1 has an advantage over typical vision testing: it can be used to describe the threshold of visual quality and to generate contrast sensitivity function (CSF). The ability to assess low contrast vision with contrast sensitivity often affords enhanced sensitivity to changes in visual function compared to high contrast visual acuity.2 Degradation in quality of vision has been attributed to a decrease in the ability to attain maximum resolution and a reduction in CSF.3

Refractive surgery involves ablating tissue in the cornea, which introduces optical aberrations that can reduce contrast sensitivity and the CSF during the surgical recovery period. Contrast sensitivity and CSF after LASIK or photorefractive keratectomy (PRK) has been shown to be reduced, at least temporarily, during the recovery period, with the decrease attributed to increases in ocular aberrations.4–13 But advances including wavefront-guided (WFG) ablations, which treat lower order and higher order aberrations, and wavefront-optimized (WFO) ablations, which add peripheral treatment to minimize spherical aberration, reduce the amount of higher order aberrations induced by refractive surgery.14–16 Patients treated with advanced ablations have been shown to perform better on contrast sensitivity testing than patients treated with conventional laser treatments.17–19

Continued advances in ablation and surgical techniques have resulted in reduced disruption of the cornea, allowing for more moderated wound healing of the reshaped cornea. For example, the implementation of femtosecond laser technology has resulted in safer, more predictable, and precise LASIK flaps.20 Although advanced ablations have been shown to improve contrast sensitivity, prospective comparisons of advanced surgical procedure and ablations that include LASIK and PRK are lacking. The overall prospective study examined multiple factors after advanced keratorefractive surgery including the primary outcome measures of the study: visual outcomes, objective image quality, task performance, and visual performance as measured by contrast sensitivity. Visual outcomes and task performance were previously published by Sia et al.15 and Ryan et al.16

This article presents visual outcomes as measured by contrast sensitivity. More specifically, this study compared high contrast and small letter contrast sensitivity, as well as the CSF among participants undergoing WFG or WFO PRK or LASIK for the treatment of myopia or myopic astigmatism 12 months after surgery.

Patients and Methods

This prospective, randomized study included U.S. military participants electing to undergo either PRK or LASIK after a comprehensive eye evaluation. After counseling on the risks and benefits of participation of the study, personnel aged 21 years or older with refractive stability for 12 months prior to surgery and myopia ranging from -0.50 to −7.25 diopters (D), with less than 3.50 D of manifest cylinder, were randomized to undergo either WFO or WFG treatment (Figure A, available in the online version of this article). Surgery was performed by four surgeons (RDS, JFP, KSB) at two institutions and laser-specific nomograms developed at each center were used to plan surgical treatments. Ablation zone was up to 9 mm with varying transition zones depending on individual treatment plans for WFO treatments and 8 mm with no transition zone for WFG treatments. The institutional review boards at Walter Reed National Military Medical Center and the U.S. Army Medical Research and Materiel Command granted approval prior to initiation of this study. Research adhered to the tenets of the Declaration of Helsinki and complied with the U.S. Health Insurance Portability and Account-ability Act. The trial was registered at the U.S. National Institutes of Health web site (NCT01097525). A summary of each surgical procedure is presented in Figure A. Uncorrected (UDVA) and corrected (CDVA) distance visual acuity, manifest refraction, corrected Super Vision Test (Precision Vision, La Salle, IL) high contrast (SV-HC), corrected Super Vision Test small letter (equivalent to 20/25) contrast sensitivity (SV-CS), mesopic pupil size, and CSF were assessed preoperatively and at 1, 3, 6, and 12 months postoperatively. UDVA and CDVA were measured using a Snellen chart viewed at a distance equivalent to 20 feet (6 meters). When scoring the Super Vision Test, SV-HC was recorded as the logarithm of the minimum angle of resolution (logMAR) a credit of −0.02 logMAR units was calculated for each letter correctly identified.21 For SV-CS, a credit of 0.05 logarithm of the contrast sensitivity (logCS) units was calculated for each letter correctly identified. The Super Vision Test, with a screen luminance of 106 cd/m2, was performed on each eye using best spectacle correction viewed 4 meters from the display in an otherwise dark room. Pupils were measured in a dark room with a handheld pupilometer (Neuroptics, Irvine, CA).

Summary of study population and surgical procedures. *Withdrawn prior to treatment. WFG = wavefront-guided; WFO = wavefront-optimized; PRK = photorefractive keratectomy; D = diopters

Figure A.

Summary of study population and surgical procedures. *Withdrawn prior to treatment. WFG = wavefront-guided; WFO = wavefront-optimized; PRK = photorefractive keratectomy; D = diopters

CSF was generated monocularly by measuring responses to a series of vertical sinusoidal gratings of the following spatial frequencies: 1.5, 3.0, 6.1, 13.1, and 19.7 cycles per degree (cpd) using the Metropsis Visual Stimulus Generation Device (Cambridge Research Systems Ltd, Kent, United Kingdom). After a demonstration, the contrast threshold for each spatial frequency was measured by a two-alternative, forced-choice, linear staircase adaptive procedure with a vertical Gabor grating stimulus at a mean luminance of 50.0 cd/m2 at a 1.71 meters viewing distance in an otherwise dark room. Preoperatively, testing was completed using habitual correction; postoperatively, testing was conducted without correction. Contrast threshold was converted to contrast sensitivity and a function over the five spatial frequencies was plotted. To compare CSF as a single value, the area under the logarithm of CSF (AULCSF) for each eye, at each visit, was calculated by developing a third order polynomial from the CSF on a logarithmic scale and integrated between the fixed limits of lowest and highest log spatial frequency according to Applegate et al.22,23

One-way analysis of variance (ANOVA) was performed to compare continuous data and Fisher exact test for categorical data preoperatively and 12 months postoperatively. For analysis over time, repeated measures ANOVA was used to compare WFG PRK versus WFO PRK versus WFG LASIK versus WFO LASIK high contrast and small letter contrast sensitivity, and CSF performance. Linear regression analysis was used to examine interrelationships between the dependent variable of 12 months postoperative AULCSF and selected preoperative variables. SPSS software (version 21.0; (IBM Corporation, Armonk, NY) was used for all statistical analyses. Given the three primary response variables of contrast (SV-HC, SV-CS, and AULCSF) examined in this study, a Bonferroni corrected P value less than .017 was considered statistically significant.

Results

In this study, 430 eyes of 215 participants were enrolled and underwent WFG PRK, WFO PRK, WFG LASIK, or WFO LASIK. Baseline and demographic characteristics are compared among the four treatment groups in Table 1. At 12 months postoperatively, 188 of 215 (87.4%) participants completed 12 months of follow-up. A comparison of 12-month outcomes between treatment groups is presented in Table 2. A pairwise comparison of preoperative to 12-month CDVA showed a significant improvement in all groups (P < .017). The change in CDVA was also significantly different between groups as determined by one-way ANOVA (P = .003). Tukey HSD post-hoc analysis revealed WFG PRK (−0.05 ± 0.07 logMAR) significantly improved from preoperatively compared to WFO LASIK (−0.02 ± 0.05 logMAR) (P = .002).

Demographics and Baseline Characteristicsa

Table 1:

Demographics and Baseline Characteristics

Between-Group Comparison 12 Months Postoperativelya

Table 2:

Between-Group Comparison 12 Months Postoperatively

A repeated measures ANOVA with a Greenhouse–Geisser correction showed that mean SV-HC differed significantly over time (P < .001). However, there was not a significant difference between treatment groups at each time point (P = .22). Pairwise comparisons between time points revealed that SV-HC improved significantly compared to preoperatively at 3 months postoperatively (P < .001) (Figure 1). Using best correction, the change at 12 months in SV-HC from preoperatively was not significantly different between groups as determined by one-way ANOVA (P = .13).

Super Vision Test (Precision Vision, LaSalle, IL) high contrast (SV-HC) of treatment groups over time. A decrease in logMAR value indicates improvement. WFG = wavefront-guided; WFO = wavefront-optimized; PRK = photorefractive keratectomy

Figure 1.

Super Vision Test (Precision Vision, LaSalle, IL) high contrast (SV-HC) of treatment groups over time. A decrease in logMAR value indicates improvement. WFG = wavefront-guided; WFO = wavefront-optimized; PRK = photorefractive keratectomy

There was also a statistically significant difference over time in SV-CS (P < .001). However, there was not a significant difference between treatment groups (P = .06). Pairwise comparisons between time points revealed SV-CS worsened significantly at 1 month but improved significantly at 3 months postoperatively (P < .001) for all groups (Figure 2). Using best correction, there was not a significant improvement in SV-CS at 12 months from preoperatively between groups, but it was suggestive as determined by one-way ANOVA (P = .019). A repeated measures ANOVA with a Greenhouse–Geisser correction found mean AULCSF did not differ significantly between groups and time (P = .09). There was also not a significant difference between treatment groups (P = .16). Pairwise comparisons between time points showed a significant difference 1 month postoperatively from preoperatively (P < .001) but no significant differences otherwise (P > .11) (Figure 3). Looking at the change in AULCSF from preoperatively to 1 month, there was no significant difference between groups (P = .091). The change at 12 months (uncorrected) in AULCSF from preoperatively (habitual correction) between groups was also not significantly different between groups as determined by one-way ANOVA (P = .61). Figure B (available in the online version of this article) presents the CSF for each treatment group at each time point.

Super Vision Test (Precision Vision, LaSalle, IL) small letter contrast sensitivity (SV-CS) of treatment groups over time. An increase in logarithm of the contrast sensitivity (logCS) indicates improvement. WFG = wavefront-guided; WFO = wavefront-optimized; PRK = photorefractive keratectomy

Figure 2.

Super Vision Test (Precision Vision, LaSalle, IL) small letter contrast sensitivity (SV-CS) of treatment groups over time. An increase in logarithm of the contrast sensitivity (logCS) indicates improvement. WFG = wavefront-guided; WFO = wavefront-optimized; PRK = photorefractive keratectomy

Area under the log contrast sensitivity function of treatment groups over time. WFG = wavefront-guided; WFO = wavefront-optimized; PRK = photorefractive keratectomy

Figure 3.

Area under the log contrast sensitivity function of treatment groups over time. WFG = wavefront-guided; WFO = wavefront-optimized; PRK = photorefractive keratectomy

Contrast sensitivity function (CSF) of each treatment group (A) preoperatively and at (B) 1, (C) 3, and (D) 12 months postoperatively. WFG = wavefront-guided; WFO = wavefront-optimized; PRK = photorefractive keratectomy

Figure B.

Contrast sensitivity function (CSF) of each treatment group (A) preoperatively and at (B) 1, (C) 3, and (D) 12 months postoperatively. WFG = wavefront-guided; WFO = wavefront-optimized; PRK = photorefractive keratectomy

Regression analyses were conducted to examine the relationship between AULCSF 12 months postoperatively and various potential predictors. A linear regression determined 12-month AULCSF was positively and significantly correlated with preoperative AULCSF r2 = 0.163, (P < .001) (Figure C, available in the online version of this article). Multiple regression modeling with 10 preoperative predictors and the dependent variable of 12-month AULCSF produced r2 = 0.187 (P < .001). Preoperative AULCSF and pre-operative mean spherical equivalent had significant positive regression weights indicating that, after accounting for other variables, preoperative AULCSF and preoperative mean spherical equivalent were significant predictors of 12-month AULCSF. Age, sex, type of surgery, preoperative cylinder, pupil size, SV-CS, SV-HC, preoperative CDVA, and type of laser treatment did not contribute to the multiple regression model. Table A (available in the online version of this article) summarizes the descriptive statistics and results of the regression. Figure C illustrates the relationship between 12-month AULCSF and preoperative AULCSF.

The relationship between 12-month and preoperative area under the log contrast sensitivity function (AULCSF).

Figure C.

The relationship between 12-month and preoperative area under the log contrast sensitivity function (AULCSF).

Descriptive Statistics of Regression Analysis

Table A:

Descriptive Statistics of Regression Analysis

Discussion

In this prospective study, there was no significant decrease in corrected high contrast visual acuity, corrected small letter contrast sensitivity, or uncorrected AULCSF in any treatment group at the 12-month follow-up, indicating that all treatments produce comparable efficacy and potential improvements in vision 12 months following surgery. Furthermore, both visual acuity and small letter contrast sensitivity improved significantly compared to preoperatively in each group 3 months postoperatively, indicating the efficacy of these various interventions. As reported by Schallhorn et al.,24 subjective and objective measures of quality of vision are not consistently related, making it challenging to discriminate risk factors of those more likely to express dissatisfaction prior to undergoing refractive surgery. Therefore, it is important to examine additional objective measures to better describe or elucidate quality of vision in an attempt to detect rationale for finer visual complaints in otherwise normal acuity participants.25 Measurement of contrast sensitivity and AULCSF has been shown to be valuable in assessing quality of vision after refractive surgery.1,10,25,26

Studies5,27 have found that contrast sensitivity is temporarily depressed in the early postoperative period but recovers after 3 months. In the current study, time-dependent changes in high contrast visual acuity and small letter contrast sensitivity and AULCSF significantly decreased at 1 month, with recovery thereafter. In the early postoperative period, stromal remodeling and wound healing in both PRK and LASIK and epithelial growth and reorganization in PRK contribute to diffusing the light rays passing through the cornea, thereby decreasing the retinal image contrast and subjective measures of contrast sensitivity.28 Factors degrading the quality of the retinal image are minimized with improved ocular surface regularity, corneal shape remodeling, and diminishing inflammatory response over time.

Comparing the change at 12 months from preoperatively in CDVA between groups, all treatment groups significantly improved from preoperatively (P < .017). When comparing between groups, the change in CDVA at 12 months compared to preoperatively was significantly better in WFG PRK than in WFO LASIK. In looking at high contrast visual acuity, small letter contrast sensitivity, and AULCSF, whereas the changes over time are reflective of the change in optical quality during corneal remodeling, these changes were not significantly different between the four treatment groups. However, when examining early performance, LASIK outperformed PRK in the early postoperative period for high contrast visual acuity and small letter contrast sensitivity, a finding consistent with numerous studies1,21,29 indicating the adverse effect on high spatial frequencies. This study found there were no significant differences between WFG and WFO LASIK in the early postoperative period, with both showing comparable declines.

Because the Super Vision Test assesses high spatial frequency contrast sensitivity and high contrast visual acuity,21 contrast sensitivity changes occurring at lower spatial frequencies may be missed. Studies of the CSF have shown that there may be disparities in contrast sensitivity between lower and higher spatial frequencies and loss of sensitivity can occur at either all spatial frequencies or only restricted bands.30 Additionally, Richman et al.31 cited the peak of the CSF, usually between 3 and 6 cpd, as the predictive variable in everyday task performance. Chan et al.12 found LASIK temporarily depressed low spatial frequency contrast. However, Montés-Micó and Charman11 stated it is higher spatial frequencies that are affected by residual refractive error. The current study found AULCSF did not change significantly between groups over time. There was a significant decrease in AULCSF at 1 month in all groups, but this recovered thereafter. AULCSF may not account for the differences at higher versus lower spatial frequencies, with the overall AULCSF being the same. Some studies21,32 have reported subtler changes in vision can be detected examining higher spatial frequencies. Additionally, studies have reported clinical significance with a change of at least 0.3 logCS.33 This study did not find a difference or change of 0.3 logCS between treatment groups postoperatively, despite the postoperative testing being conducted without correction. In this study, the CSF was measured postoperatively without correction to reflect “real world” postoperative visual quality. Given the improvement in visual outcomes in all treatment groups, it may not be possible to detect the refined differences in the spatial frequencies tested.

It may also be difficult to isolate and attribute improvements due to surgery type or treatment profile under current testing parameters. This study did not include contrast sensitivity testing under glare condition. Higher order aberrations are more pronounced under glare conditions and therefore testing under this condition may be sensitive enough to capture differences.17,32,34 Williams et al.35 showed higher order aberrations in normal eyes reduce visual performance and in correcting aberrations, one can expect an improvement in contrast sensitivity, especially in patients with larger pupils. Additionally, Montés-Micó and Charman11 reported decreased contrast sensitivity after PRK under mesopic condition but not photopic. However, a study by Barretto et al.26 showed no significant differences between WFG LASIK and WFG PRK when examining photopic or mesopic contrast sensitivity 12 months postoperatively. Furthermore, Tuan and Liang17 showed improved contrast sensitivity after WFG LASIK.

Myrowitz and Chuck19 pointed out the complexity in parsing out individual advanced technology contributions. The goal of WFG treatment is to minimize the induction of higher order aberrations while treating existing higher order aberrations, whereas WFO ablations prioritize maintaining the prolate profile of the cornea, thereby limiting higher order aberrations induced by spherical aberration. Williams et al.36 pointed out the laser treatment transition zone as being deleterious in producing a good retinal image due to the altered corneal shape. Furthermore, correction of higher order aberrations in some eyes will be of greater benefit than others. Although outcomes have been positive for either treatment profile, WFG has been shown to clinically have a slight edge over WFO.15,36,37 The clinical outcomes do not necessarily correlate with visual symptoms. He and Manche38 reported lower average of symptoms in WFO PRK in some assessments when comparing WFO and WFG PRK. Similarly, Sia et al.15 found no difference in patient-reported symptoms or satisfaction when comparing WFG to WFO PRK and Yu et al.39 found satisfaction comparable between WFG and WFO LASIK.

To ascertain which variables affect 12-month visual performance as measured by AULCSF, a regression analysis was performed. It showed that the amount of preoperative mean spherical equivalent and preoperative AULCSF predicted 12-month postoperative performance (r2 = 0.187, P < .001). Patients with lower myopia and higher preoperative AULCSF were expected to perform better 12 months postoperatively. Age, sex, pupil size, surgery type, and treatment profile were not significant. Only 19% of the significant predictive variables accounted for variance in AULCSF, suggesting that although preoperative mean spherical equivalent and preoperative AULCSF significantly influence visual performance, there are other unaccounted factors. As observed by the comparative analysis in the study, treatment profile and surgery type were not significant at 12 months. Other studies have shown increasing age and pupil diameter to be factors affecting lower contrast sensitivity.40 However, in the current study, the comparable young age among the treatment groups was not a significant factor in visual performance.

It should be noted that some of the improvement in vision reported following refractive surgery is attributable to magnification of the retinal image with correction of myopia at the corneal plane.41 However, because the ultimate vision achieved did not differ between groups and no appreciable decrease in vision was detected, these optical corrections are less important.

WFG and WFO PRK and LASIK procedures maintained high contrast visual acuity and small letter contrast sensitivity and the CSF. Post-hoc tests comparing one group to another showed the change from preoperatively in WFG PRK was significantly better than WFO LASIK when measuring CDVA and Super Vision Test small letter contrast sensitivity (Table 2). Although the recovery period for visual performance was longer for PRK versus LASIK, at 12 months postoperatively, there was no significant difference in treatment type or treatment profile. These finding suggest that high and low contrast visual acuity and contrast sensitivity with smaller letter sizes (20/25 to 20/50) are most sensitive for monitoring visual improvements and decrements following corneal refractive surgery.

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Demographics and Baseline Characteristicsa

CharacteristicWFG PRKWFO PRKWFG LASIKWFO LASIKPb
No. of participants55 (110 eyes)53 (106 eyes)51 (102 eyes)56 (112 eyes)
Age (y)30.4 ± 6.6 (21 to 46)30.1 ± 6.0 (21 to 51)31.0 ± 7.5 (21 to 50)31.7 ± 7.1 (21 to 50).33
Male/female44/1140/1340/1146/10
Manifest sphere (D)−3.22 ± 1.72 (−0.50 to −7.25)−3.12 ± 1.46 (−1.00 to −7.25)−3.38 ± 1.33 (−0.75 to −6.75)−3.42 ± 1.49 (−1.25 to −7.00).43
Manifest cylinder (D)−0.76 ± 0.61 (−0.00 to −2.50)−0.63 ± 0.52 (−0.00 to −2.50)−0.58 ± 0.54 (−0.00 to −2.50)−0.68 ± 0.67 (−0.00 to −3.25).13
MSE (D)−3.60 ± 1.74 (−0.75 to −7.63)−3.43 ± 1.52 (−1.00 to −7.75)−3.67 ± 1.30 (−1.38 to −7.13)−3.76 ± 1.51 (−1.50 to −7.25).44
UDVA (logMAR)1.10 ± 0.471.10 ± 0.421.14 ± 0.371.16 ± 0.40.70
CDVA (logMAR)−0.10 ± 0.05−0.11 ± 0.05−0.09 ± 0.04−0.10 ± 0.04.14
Ablation depth (μm)58.5 ± 22.553.3 ± 19.959.9 ± 18.058.9 ± 20.6.09
Pupil size (mm)6.56 ± 0.706.50 ± 0.836.42 ± 0.796.56 ± 0.83.52

Between-Group Comparison 12 Months Postoperativelya

CharacteristicWFG PRKWFO PRKWFG LASIKWFO LASIKPb
No. of participants48 (96 eyes)48 (96 eyes)43 (86 eyes)49 (98 eyes)
MSE (D)−0.03 ± 0.34−0.12 ± 0.300.01 ± 0.26−0.15 ± 0.18< .001
UDVA (logMAR)c−0.09 ± 0.08−0.10 ± 0.08−0.09 ± 0.090.08 ± 0.08.38
Change in CDVA (logMAR)c−0.05 ± 0.07−0.03 ± 0.06−0.03 ± 0.06−0.02 ± 0.05.003
Change in SV-HC (logMAR)c−0.05 ± 0.06−0.04 ± 0.07−0.05 ± 0.05−0.04 ± 0.06.13
Change in SV-CS (logCS)d0.17 ± 0.180.12 ± 0.190.14 ± 0.220.08 ± 0.22.019
Change in AULCSF−0.03 ± 0.17−0.02 ± 0.200.00 ± 0.170.00 ± 0.14.61

Descriptive Statistics of Regression Analysis

VariableMean ± SDCorrelation With 12 Mo AULCSFMultiple Regression Weights

βP
Age30.83 ± 6.92−0.040.003.95
Sex1.79 ± 0.41−0.02−0.006.92
Pupil size6.51 ± 0.80−0.020.002.99
PRK/LASIK1.49 ± 0.50−0.030.013.80
WFG/WFO1.52 ± 0.50−0.06−0.027.57
Pre MSE−3.64 ± 1.550.18a0.135.008a
Pre cylinder−0.68 ± 0.610.06−0.011.83
Pre CDVA−0.10 ± 0.04−0.070.065.24
Pre SV-HC−0.10 ± 0.07−0.14−0.042.55
Pre SV-CS0.95 ± 0.210.170.046.50
Pre AULCSF2.03 ± 0.150.40a0.379< .001a
Authors

From Warfighter Refractive Eye Surgery Program and Research Center, Fort Belvoir Community Hospital, Fort Belvoir, Virginia (DSR, RKS, BAR, JBE, LAL); Visual Neurophysiology Service, University of the Incarnate Word Rosenberg School of Optometry, San Antonio, Texas (JR); Ophthalmology Service, Walter Reed National Military Medical Center, Bethesda, Maryland (RDS, JFP); The Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland (KSB).

U.S. National Institute of Health Clinical Trial No. NCT01097525.

The authors have no financial or proprietary interest in the materials presented herein.

The views expressed in this article are those of the authors and do not reflect the official policy of the Department of Army/Navy/Air Force, Department of Defense, or U.S. Government.

Supported by a U.S. Army Medical Research Acquisition Activity Award W81XWH-09-2-0018.

AUTHOR CONTRIBUTIONS

Study concept and design (KSB); data collection (DSR, JBE, LAL); analysis and interpretation of data (DSR, RKS, JR, BAR, RDS, JFP, KSB); writing the manuscript (DSR); critical revision of the manuscript (RKS, JR, BAR, RDS, JFP, JBE, LAL); statistical expertise (DSR, RKS); administrative, technical, or material support (JR, BAR, RDS, JFP, JBE, LAL); supervision (BAR, RDS, KSB)

Correspondence: Denise S. Ryan, MS, Warfighter Refractive Eye Surgery Program and Research Center at Fort Belvoir, Fort Belvoir Community Hospital, 9300 DeWitt Loop, Fort Belvoir, VA 22060. E-mail: denise.s.ryan.ctr@mail.mil

Received: April 17, 2018
Accepted: July 03, 2018

10.3928/1081597X-20180716-01

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