The goal of most patients in pursuing refractive surgery is to achieve the best possible level of spectacle free vision. Although LASIK is the most commonly selected refractive procedure for rapid postoperative recovery, photorefractive keratectomy (PRK) is also widely used for patients at risk for ectasia and for those who wish to avoid potential flap complications intraoperatively and in the future.1–4
Conventional ablation profiles have yielded good results but also have a tendency to generate higher-order aberrations, which have been implicated as a potential contributing factor to symptoms of night-time glare, halos, haze, and starbursts.1,5 Recent innovations to reduce these higher-order aberrations include the U.S. Food and Drug Administration approved wavefront-guided (WFG) and wavefront-optimized (WFO) laser ablation profiles. Both have been shown to have advantages over conventional ablation profiles.2,6–8 WFO profiles give additional treatment to the peripheral cornea to preserve the naturally prolate shape without addressing the preexisting higher-order aberrations of the eye.6,7 WFG treatments require a preoperative measurement of the eye’s aberrations and aims to correct those that are present.6,7 It is unclear at this time which profile is the most successful at achieving the goal of optimal vision.9
Although there are multiple metrics to measure the efficacy of refractive surgery, it has been suggested that patient satisfaction is an important factor by which to judge the success of the treatment.6 Patients have generally been reported to be highly satisfied with LASIK, with rates reported between 95% and 100%.10,11 Several studies have attempted to refine this further by asking patients about the various components contributing to quality of vision.2
This study prospectively compares WFG and WFO treatment profiles on healthy eyes without previous refractive surgery to determine their effect on patient self-reported symptoms such as glare, halos, haze, visual clarity, and overall perceived quality of vision. This can help determine whether there is an optimal treatment profile for refractive surgery.
Patients and Methods
After institutional review board approval was obtained for this prospective, randomized, fellow eye controlled study, 142 eyes of 71 patients were enrolled from the refractive surgery service of Stanford University School of Medicine. Power calculations were performed to be 80% or greater. The trial was publicly registered with the National Institutes of Health at http://www.clinicaltrials.gov/ (NCT01135719). Written informed consent was obtained from all patients prior to enrollment in the study and strict adherence with the Health Insurance Portability and Accountability Act (HIPAA) and the tenets of the Declaration of Helsinski was maintained.
Inclusion criteria were: less than 12.00 diopters (D) of spherical myopia with less than 3.00 D of refractive astigmatism; stable refraction documented by a change in sphere and cylinder less than 0.50 D in the previous 12 months; discontinuation of soft contact lens wear 7 days or more before the preoperative evaluation; visual acuity correctable to 20/20 or better in both eyes; 21 years of age or older; and willing and able to return for scheduled follow-up examinations for 12 months after their PRK surgery.
Exclusion criteria for this study were: rigid gas-permeable contact lens use; severe ocular surface disease, corneal abnormalities, keratoconus or other ectactic disorders; cataracts; baseline difference of greater than 0.75 D in sphere power between standard manifest and cycloplegic refractions; baseline difference of greater than 0.5 D in cylinder power between standard manifest and cycloplegic refractions; connective tissue disease or diabetes mellitus; steroid responders; history of glaucoma; macular pathology; pregnant or lactating patients; patients with sensitivity to planned study medications; or patients participating in another ophthalmic drug or device clinical trial.
Patients’ dominant eye was randomized to undergo either WFG PRK treatment by the VISX CustomVue Star S4 IR excimer laser system (Abbott Medical Optics, Inc., Santa Clara, CA) or WFO PRK treatment by the Wavelight Allegretto Wave Eye-Q 400 Hz excimer laser system (Alcon Laboratories, Inc., Fort Worth, Texas). The fellow eye was treated with the other laser platform to serve as a control. Dominance was determined by the Dolman method also known as the hole-in-the-card test.12 Each patient had comprehensive eye examinations performed before PRK and at each subsequent follow-up visit, including measurements of their manifest refraction, corrected distance visual acuity, 5% and 25% contrast corrected distance visual acuity, and higher-order aberration analysis with the VISX WaveScan aberrometer (Abbott Medical Optics, Inc.). 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 selected. One surgeon (EEM) performed the PRK surgery in all cases. An Amoils epithelial scrubber (Innovative Excimer Solutions, Inc., Toronto, Canada) was used to remove the epithelium over an 8.0-mm zone centered over the pupil and ablation was targeted for full correction. Autocentration and iris recognition were used in all cases. No adjunct mitomycin C was used in any of the cases. Neither the patient nor the surgeon knew which treatment their eye had been randomized to until the day of the surgery. A bandage contact lens (Acuvue Oasys; Johnson & Johnson Vision Care, Inc., New Brunswick, NJ) was placed after the surgery and topical moxifloxacin 0.5% (Alcon Laboratories, Inc.) was administered four times a day until the epithelium was healed. Patients were also given a taper of topical steroids–fluorometholone ophthalmic solution 0.1 % (FML; Allergan, Irvine, CA) four times a day for 2 weeks and then twice a day for 2 weeks.
The patients answered questionnaires on their visual symptoms and quality of vision for each eye at baseline and again at 1, 3, 6, and 12 months after surgery. Our group has previously used this questionnaire in several other studies and a copy of it is available as supplementary material.2,12–14 Patients were asked to grade their symptoms of day and nighttime glare and clarity, halos, haze, fluctuating vision, and double or ghost images on a scale of 0 to 10, where 0 represented no problems and 10 corresponded to a disabling problem. They were also asked how strongly they agreed with the statement “My vision is excellent,” where 0 represented strongly agree and 10 represented strongly disagree. An average was also taken of all questions as a composite measure of patient’s visual symptoms. No changes were made to outcome measures after initiation of the trial. A paired t test was used to compare symptom severity between the two treated eyes and also between preoperative and postoperative symptoms. Finally, patients were asked to determine which eye had better vision: right, left, same, or unknown. A chi-square test was used to compare the distribution of preferred eye between the two groups. A separate analysis was performed by separating patients into subgroups with root-mean-square higher-order aberrations of 0.3 or more microns or less than 0.3 microns. Only patients who had both eyes fall into the same group were included.
Figure 1 summarizes the recruitment of the patients and their progress through the study. The trial ended when predetermined recruitment goals were met. Of the 71 patients enrolled, 24 were male and 47 were female and had a median age of 36 years (range: 23 to 61 years). Table 1 shows the preoperative characteristics of the eyes enrolled to each type of treatment. The eyes were similar in their lower- and higher-order aberrations, although WFO eyes had significantly less sphere and more cylinder than WFG eyes. There were no intraoperative or postoperative complications noted over the course of the study. There were no differences in rates of reepithelialization or bandage contact lens removal between the two eyes.
Flow diagram of patient enrollment and progression through the trial.
Baseline Characteristics of Eyes Randomized to the Wavefront-Guided and Wavefront-Optimized Groups
Figure 2 shows patients’ baseline levels of halos, haze, glare, clarity, fluctuating vision, double vision, and the extent to which they felt their vision was excellent. No significant differences were found between patients assigned to either group (P ⩾ .065). However, there were significantly more reports of better daytime clarity in the WFG eyes (P = .049). When scores for all symptoms were averaged, there were no differences between the two treatment groups (P = .654). There were no significant differences between the two groups (P ⩾ .059) except at 6 months, when patients more strongly agreed that their WFG eyes had excellent vision (P = .029). However, this difference was no longer significant at 12 months (P = .109). Figure 3 shows patients’ reported visual symptoms after 12 months.
(A) Patient reported severity score of visual symptoms scored from 0 to 10, with 0 being no symptoms and 10 being disabling symptoms. (B) Mean difference of scores between wavefront-guided and wavefront-optimized eyes preoperatively.
(A) Patient reported severity score of visual symptoms scored from 0 to 10, with 0 being no symptoms and 10 being disabling symptoms. (B) Mean difference of scores between wavefront-guided and wavefront-optimized eyes at 12 months.
At 1 month, composite symptoms increased from baseline for both groups (P = .000). However, there were no differences between the two treatment groups in terms of individual symptoms (P ⩾ .080) or overall (P = .434). At 3 months, there was no longer a significant difference in average symptoms from baseline (P = .734 WFG, P = .918 WFO). At 6 months, the WFG eyes had significantly fewer average visual disturbances than baseline (P = .041) but the difference was not significant in the WFO eyes (P = .120). At 12 months, the groups were reversed. Eyes receiving WFG treatment did not have a difference in averaged symptoms (P = .164), but eyes receiving WFO treatment were experiencing fewer visual disturbances (P = .005). Throughout the studied period, there were no significant differences between the groups in terms of averaged symptoms (P ⩾ .375) except at 12 months. At that point, patients experienced fewer symptoms in the WFO eye overall (P = .044). When comparing individual symptoms, more patients reported having excellent vision in the WFO group from 3 months onward compared with baseline (P = .000 at 12 months and .002 at 3 months). Similarly for the WFG eyes, there was a significant increase in perceived excellent vision starting at 3 months and persisting throughout the rest of study (WFG: 1.54 at 3 months, 2.23 at 6 months, and 2.24 at 12 months; WFO: 1.57 at 3 months, 1.86 at 6 months, and 2.51 at 12 months; P = .003 at 3 months and .000 at 6 and 12 months). In this group, there was also a significant improvement in nighttime glare compared to baseline starting at 6 months (P ⩽ .023). Patients also reported less nighttime glare compared to baseline starting at 6 months (P ⩽ .030) in the WFO eyes.
When patients were separated by higher-order aberrations of 0.3 or more microns, 37 (55%) of the 71 patients were included. There again were no significant differences between the two treatment groups at baseline (P ⩾ .058). This continued to be true for months 1 to 6 (P ⩾ .102 at 1 month, .213 at 3 months, and .262 at 6 months). However, at 12 months, patients in the WFO group reported significantly fewer problems with clarity during the day and at night (P = .035 and .040, respectively). No other symptoms were significantly different at 12 months (P ⩾ .067). The averaged symptoms showed a similar trend that was not significantly different prior to 12 months (P ⩾ .204) and WFO treatment resulted in fewer average visual symptoms at 12 months (P = .039). For higher-order aberrations less than 0.3 microns, 15 (21%) of the 71 patients were included. There were no differences between the treatment groups at any time point (P ⩾ .054). The other patients (19) were excluded from this analysis because their two eyes fell on different sides of the 0.3-micron cut-off.
Figure 4 shows patients’ choice when asked to determine which eye had better vision. At the first postoperative month visit, there was a significant increase in patients who preferred the WFO eye (P = .005). However, this difference disappeared at the next visit (3 months). There was no change in the distribution of preferred eyes compared to baseline after 3 months (P ⩾ .076).
Patient self-reported better eye at times surveyed.
There has been much interest in investigating the quality of vision after refractive surgery, after both LASIK and PRK.15–17 There are many parameters (visual acuity, contrast sensitivity, level of higher-order aberrations, and residual refractive error) that may be used to determine the optimal treatment profile for refractive surgery. However, the patient’s satisfaction with his or her quality of vision may be an important factor underlying the success of the surgery. Bühren et al. showed that there may only be a low correlation between subjective quality of vision and psychophysical tests such as contrast sensitivity or wavefront data.18 They did find high correlations between subjective experiences of visual symptoms such as glare, halos, blur, starbursts, and the overall quality of vision.18
Previous investigations have demonstrated the safety and efficacy of WFG PRK in achieving the desired amount of refractive correction.2,8 Similar results have been shown for WFO treatments in PRK.3 Falavarjani et al. compared a topography-guided platform to the WFO platform in patients undergoing PRK and found that uncorrected distance visual acuity and contrast sensitivity were similar across treatment platforms.19 Manche and Haw studied WFG PRK compared with LASIK and found that patients receiving PRK had a longer recovery period but all parameters (uncorrected visual acuity, higher-order aberrations, subjective symptoms) became similar between the two groups after 3 months.2
Several other studies have compared the quality of vision after WFG and WFO treatments in patients undergoing LASIK.19–23 Some of these studies have shown no difference between the two profiles.20,23 However, some studies suggested improved outcomes with WFG treatment.21,23 There has been considerably less investigation into the differences in these treatment profiles in patients undergoing PRK. Moshifar et al. performed the only other published study to date that compares WFO and WFG treatment profiles in patients undergoing PRK.24 They compared WFO and WFG treatments in fellow eyes of 23 patients over 3 months and found that there were no significant differences in best achieved uncorrected distance visual acuity or higher-order aberrations between the two groups. It has been shown that custom ablation profiles in refractive surgery are able to reduce higher-order aberrations compared to the conventional, but no profile has been shown be substantially superior to the others and most profiles still increase higher-order aberrations, although to different extents.25
Moshifar et al. were unable to draw conclusions from their subjective surveys regarding patients’ experiences perceived quality of vision.24 Earlier, Yu et al. observed 100 patients randomized to WFG treatment or WFO LASIK treatment in both eyes with questionnaires directed at patient satisfaction.26 They showed no difference between the two groups in terms of patient satisfaction. Patients were observed for 6 months and questioned about the level of glare, halos, light sensitivity, fluctuations of vision, ghost images, and starbursts they experienced. They again found no differences between the two treatment groups except perhaps an increase in ghost images in the WFO group at 6 months.26
The results of this study are consistent with those previously performed that show no differences in patient symptoms in aggregate or when looking at individual questions on experiences of glare, halos, haze, vision clarity, and starbursts. Similar to previous studies, symptoms increased from baseline at 1 month but returned to preoperative levels from 3 months onward.2 This reversal in the symptoms was most likely due to epithelial remodeling.27 It has been suggested that WFG LASIK may benefit patients who have larger higher-order aberrations.22,28 We performed post-hoc subgroup analysis by separating patients by higher-order aberrations using a threshold of 0.3 microns as previously suggested to investigate this question in these patients with PRK.23 Our patient population may be slightly different from the U.S. Food and Drug Administration trial in that 55% of our patients had higher-order aberrations greater than 0.3 microns compared to only 17% in Stonecipher and Kezirian’s study.22 We found no differences in aggregate and for most individual symptoms for the first 6 months. However, with higher levels of higher-order aberrations, patients in the WFO group reported significantly fewer problems with clarity during the day and at night (P = .035 and .040, respectively) a year after their procedure. There was also a significant preference in patients for the WFO eye at 1 month (P = .005), although this difference disappeared at 3 months and thereafter. Finally, at 12 months patients had lower composite symptom scores in the WFO group overall and when separated by high higher-order aberrations levels (P = .044 and .039, respectively). Taken all together, this may indicate that WFO ablation profiles are equally effective in eyes with average and higher preoperative levels of higher-order aberrations.
We evaluated several potential questionnaires when designing this study. The NEI Quality of Life Questionnaire is the most commonly used questionnaire for ophthalmic studies.29 We elected not to use this questionnaire due to its design as a binocular assessment tool and its lack of specific questions directed at the most commonly reported symptoms associated with LASIK and PRK surgery (ie, halos, glare, etc). We were unable to identify any monocular validated questionnaires that were designed specifically to measure the symptoms that are commonly reported with keratorefractive surgical procedures when we began our study. Due to the lack of a suitable questionnaire and our contralateral study design, we used a previously validated survey2,12–14 to investigate a multitude of components (glare, halos, clarity, haze, double vision, and starbursts) that may contribute to patients’ overall quality of vision. Several excellent validated questionnaires have subsequently been developed that specifically measure quality of vision in subjects undergoing refractive surgery.30 This questionnaire and others should help standardize quality of vision reporting following keratorefractive surgery in future studies.
WFG treatments may be difficult to perform due to the challenge of obtaining aberrometry images. In Perez-Straziota et al.’s retrospective comparison of the two treatment profiles, 14 of 66 (21%) eyes were scheduled for but unable to complete WFG treatment because of alignment or inconsistencies with their manifest refraction.31 In our study, we were able to perform high quality wavefront analysis of all enrolled patients. If WFO treatments are easier than WFG treatments, practices may consider using them instead because they can be more easily and reliably performed.
To date, this is the largest prospective study with the longest follow-up investigating the visual differences experienced by patients receiving these excimer ablation profiles for PRK. Even though the enrollment in this study is larger than the numbers required by our initial power calculation, it was not specifically designed to investigate differences in patients with high levels of higher-order aberrations. Additionally, although surveys of patients’ subjective symptoms may be a good gauge of their quality of vision, it may be difficult for patients to distinguish between their two eyes when answering questions directed at each individually. The most robust conclusions can be drawn from the average of all symptoms questioned in our survey and this did not show any differences between the two types of treatments. Further investigation will more definitively yield guidelines for when patients should be treated with either profile.
- Hatch BB, Moshirfar M, Ollerton AJ, Sikder S, Mifflin MD. A prospective, contralateral comparison of photorefractive keratectomy (PRK) versus thin-flap LASIK: assessment of visual function. Clin Ophthalmol. 2011;5:451–457.
- Manche EE, Haw WW. Wavefront-guided laser in situ keratomileusis (LASIK) versus wavefront-guided photorefractive keratectomy (PRK): a prospective randomized eye-to-eye comparison (an American Ophthalmological Society thesis). Trans Am Ophthalmol Soc. 2011;109:201–220.
- Nassiri N, Safi S, Aghazade Amiri M, et al. Visual outcome and contrast sensitivity after photorefractive keratectomy in low to moderate myopia: wavefront-optimized versus conventional methods. J Cataract Refract Surg. 2011;37:1858–1864. doi:10.1016/j.jcrs.2011.05.023 [CrossRef]
- Guerin MB, Darcy F, O’Connor J, O’Keeffe M. Excimer laser photorefractive keratectomy for low to moderate myopia using a 5.0 mm treatment zone and no transitional zone: 16-year follow-up. J Cataract Refract Surg. 2012;38:1246–1250. doi:10.1016/j.jcrs.2012.03.027 [CrossRef]
- Karimian F, Feizi S, Jafarinasab MR. Conventional versus custom ablation in photorefractive keratectomy: randomized clinical trial. J Cataract Refract Surg. 2010;36:637–643. doi:10.1016/j.jcrs.2009.10.050 [CrossRef]
- Myrowitz EH, Chuck RS. A comparison of wavefront-optimized and wavefront-guided ablations. Curr Opin Ophthalmol. 2009;20:247–250. doi:10.1097/ICU.0b013e32832a2336 [CrossRef]
- Schallhorn SC, Farjo AA, Huang D, et al. Wavefront-guided LASIK for the correction of primary myopia and astigmatism a report by the American Academy of Ophthalmology. Ophthalmology. 2008;115:1249–1261. doi:10.1016/j.ophtha.2008.04.010 [CrossRef]
- Bababeygy SR, Manche EE. Wavefront-guided photorefractive keratectomy with the VISX platform for myopia. J Refract Surg. 2011;27:173–180.
- Smadja D, Reggiani-Mello G, Santhiago MR, Krueger RR. Wavefront ablation profiles in refractive surgery: description, results, and limitations. J Refract Surg. 2012;28:224–232. doi:10.3928/1081597X-20120217-01 [CrossRef]
- McGhee CN, Craig JP, Sachdev N, Weed KH, Brown AD. Functional, psychological, and satisfaction outcomes of laser in situ keratomileusis for high myopia. J Cataract Refract Surg. 2000;26:497–509. doi:10.1016/S0886-3350(00)00312-6 [CrossRef]
- Brown MC, Schallhorn SC, Hettinger KA, Malady SE. Satisfaction of 13,655 patients with laser vision correction at 1 month after surgery. J Refract Surg. 2009;25:S642–S646.
- Murakami Y, Manche EE. Prospective, randomized comparison of self-reported postoperative dry eye and visual fluctuation in LASIK and photorefractive keratectomy. Ophthalmology. 2012;119:2220–2224. doi:10.1016/j.ophtha.2012.06.013 [CrossRef]
- Chan A, Manche EE. Effect of preoperative pupil size on quality of vision after wavefront-guided LASIK. Ophthalmology. 2011;118:736–741. doi:10.1016/j.ophtha.2010.07.030 [CrossRef]
- Golas L, Manche EE. Dry eye after laser in situ keratomileusis with femtosecond laser and mechanical keratome. J Cataract Refract Surg. 2011;37:1476–1480. doi:10.1016/j.jcrs.2011.03.035 [CrossRef]
- Bailey MD, Mitchell GL, Dhaliwal DK, Boxer Wachler BS, Zadnik K. Patient satisfaction and visual symptoms after laser in situ keratomileusis. Ophthalmology. 2003;110:1371–1378. doi:10.1016/S0161-6420(03)00455-X [CrossRef]
- Brunette I, Gresset J, Boivin JF, et al. Functional outcome and satisfaction after photorefractive keratectomy: Part 2. Survey of 690 patients. Ophthalmology. 2000;107:1790–1796. doi:10.1016/S0161-6420(00)00267-0 [CrossRef]
- Brunette I, Gresset J, Boivin JF, Boisjoly H, Makni H. Functional outcome and satisfaction after photorefractive keratectomy: Part 1. Development and validation of a survey questionnaire. Ophthalmology. 2000;107:1783–1789. doi:10.1016/S0161-6420(00)00268-2 [CrossRef]
- Bühren J, Martin T, Kühne A, Kohnen T. Correlation of aberrometry, contrast sensitivity, and subjective symptoms with quality of vision after LASIK. J Refract Surg. 2009;25:559–568.
- Falavarjani KG, Hashemi M, Modarres M, Sanjari MS, Darvish N, Gordiz A. Topography-guided vs wavefront-optimized surface ablation for myopia using the WaveLight Platform: a contralateral eye study. J Refract Surg. 2011;27:13–17. doi:10.3928/1081597X-20100310-02 [CrossRef]
- Miraftab M, Seyedian MA, Hashemi H. Wavefront-guided vs wavefront-optimized LASIK: a randomized clinical trial comparing contralateral eyes. J Refract Surg. 2011;27:245–250. doi:10.3928/1081597X-20100812-02 [CrossRef]
- Padmanabhan P, Mrochen M, Basuthkar S, Viswanathan D, Joseph R. Wavefront-guided versus wavefront-optimized laser in situ keratomileusis: contralateral comparative study. J Cataract Refract Surg. 2008;34:389–397. doi:10.1016/j.jcrs.2007.10.028 [CrossRef]
- Stonecipher KG, Kezirian GM. Wavefront-optimized versus wavefront-guided LASIK for myopic astigmatism with the ALLEGRETTO WAVE: three-month results of a prospective FDA trial. J Refract Surg. 2008;24:S424–S430.
- Tran DB, Shah V. Higher order aberrations comparison in fellow eyes following intraLase LASIK with wavelight allegretto and custom cornea LADArvision4000 systems. J Refract Surg. 2006;22:S961–S964.
- Moshirfar M, Churgin DS, Betts BS, et al. Prospective, randomized, fellow eye comparison of WaveLight Allegretto Wave Eye-Q versus VISX CustomVue™ STAR S4 IR™ in photorefractive keratectomy: analysis of visual outcomes and higher-order aberrations. Clin Ophthalmol. 2011;5:1185–1193. doi:10.2147/OPTH.S24319 [CrossRef]
- AlMahmoud T, Munger R, Jackson WB. Advanced corneal surface ablation efficacy in myopia: changes in higher order aberrations. Can J Ophthalmol. 2011;46:175–181. doi:10.3129/i10-104 [CrossRef]
- Yu J, Chen H, Wang F. Patient satisfaction and visual symptoms after wavefront-guided and wavefront-optimized LASIK with the WaveLight platform. J Refract Surg. 2008;24:477–486.
- Abbas UL, Hersh PSSummit PRK Study Group. Late natural history of corneal topography after excimer laser photorefractive keratectomy. Ophthalmology. 2001;108:953–959. doi:10.1016/S0161-6420(01)00549-8 [CrossRef]
- Fares U, Suleman H, Al-Aqaba MA, Otri AM, Said DG, Dua HS. Efficacy, predictability, and safety of wavefront-guided refractive laser treatment: metaanalysis. J Cataract Refract Surg. 2011;37:1465–1475. doi:10.1016/j.jcrs.2011.02.029 [CrossRef]
- Mangione CM, Lee PP, Gutierrez PR, Spritzer K, Berry S, Hays RD. Development of the 25-item National Eye Institute Visual Function Questionnaire. Arch Ophthalmol. 2001;119:1050–1058. doi:10.1001/archopht.119.7.1050 [CrossRef]
- McAlinden C, Pesudovs K, Moore JE. The development of an instrument to measure quality of vision: the Quality of Vision (QoV) questionnaire. Invest Ophthalmol Vis Sci. 2010;51:5537–5545. doi:10.1167/iovs.10-5341 [CrossRef]
- Perez-Straziota CE, Randleman JB, Stulting RD. Visual acuity and higher-order aberrations with wavefront-guided and wavefront-optimized laser in situ keratomileusis. J Cataract Refract Surg. 2012;36:437–441. doi:10.1016/j.jcrs.2009.09.031 [CrossRef]
Baseline Characteristics of Eyes Randomized to the Wavefront-Guided and Wavefront-Optimized Groups
|Pupil size (mm)||6.47 ± 0.83||6.50 ± 0.85||0.03 (−0.03 to 0.09)||.332|
|Sphere||−5.10 ± 2.25||−4.92 ± 2.30||−0.18 (−0.35 to −0.01)||.040|
|Cylinder||0.87 ± 0.72||0.74 ± 0.73||0.13 (0.03 to 0.23)||.013|
|Spherical equivalent||−4.66 ± 2.29||−4.55 ± 2.31||−0.11 (−0.27 to 0.04)||.156|
|Root mean square error||0.35 ± 0.13||0.38 ± 0.13||−0.01 (−0.04 to 0.02)||.501|
|Spherical aberration||0.10 ± 0.12||0.11 ± 0.14||−0.01 (−0.04 to 0.02)||.448|
|Coma||0.20 ± 0.12||0.21 ± 0.12||−0.01 (−0.03 to 0.01)||.227|
|Trefoil||0.16 ± 0.09||0.17 ± 0.11||−0.03 (−0.06 to 0.01)||.113|