Journal of Refractive Surgery

Original Article 

Comparison of Measurements and Clinical Outcomes After Wavefront-Guided LASEK Between iDesign and WaveScan

Ji Won Jung, MD; Byung Hoon Chung, MD; Sun Hyup Han, BA; Eung Kweon Kim, MD, PhD; Kyoung Yul Seo, MD, PhD; Tae-im Kim, MD, PhD

Abstract

PURPOSE:

To compare the measurements of refractive errors and ocular aberrations obtained using iDesign and WaveScan (Abbott Medical Optics, Inc., Santa Ana, CA), and to compare surgical outcomes of wavefront-guided LASEK using ablation profiles based on both aberrometers.

METHODS:

Ninety myopic eyes of 45 normal patients were evaluated using both the iDesign and WaveScan to measure spherical and cylindrical errors, spherical equivalents, and Zernike coefficients of ocular aberrations. Wavefront-guided LASEK was performed in a different group of 59 eyes of 30 patients divided into two groups, the iDesign and Wavescan groups. The clinical outcomes between the two groups including uncorrected visual acuity, refractive errors, contrast sensitivity, and ocular aberration were compared at 1, 3, and 6 months postoperatively.

RESULTS:

The iDesign produced significantly higher myopic values for refractive errors than the WaveScan, as well as significantly lower levels of total higher order, third, fourth, and fifth order root mean square values and Zernike coefficients of vertical coma and spherical aberration. At postoperative 1, 3, and 6 months, there were no statistically significant differences between the two groups in terms of uncorrected visual acuity and remaining refractive errors. The percentages of patients with spherical equivalents within ±1.00 and ±0.50 diopters of emmetropia were 100% (29 eyes) and 75.9% (22 eyes), respectively, in the iDesign group and 96.7% (29 eyes) and 70.0% (21 eyes), respectively, in the WaveScan group. Mesopic contrast sensitivity values were significantly higher, and the change in root mean square values for spherical aberration was significantly lower in the iDesign group.

CONCLUSIONS:

There were significant differences between the iDesign and the WaveScan in the measurements of refraction and ocular aberrations. Wavefront-guided LASEK based on an ablation profile from the iDesign demonstrated comparable refractive predictability with the WaveScan group, resulting in minimal physician adjustment and superior postoperative visual quality.

[J Refract Surg. 2015;31(6):398–405.]

From the Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea (JWJ, BHC, SHH, EKK, KYS, TIK); the Department of Ophthalmology and Inha Vision Science Laboratory, Inha University School of Medicine, Incheon, South Korea (JWJ); and the Corneal Dystrophy Research Institute, Severance Biomedical Science Institute, and Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea (EKK).

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

Supported in part by a grant from the Korean Health Technology R & D Project, Ministry of Health & Welfare, Republic of Korea (HI14C2044) and the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science, and Technology (2013R1A1A2058907).

AUTHOR CONTRIBUTIONS

Study concept and design (JWJ, TIK); data collection (JWJ, BHC); analysis and interpretation of data (JWJ, EKK, KYS, TIK); writing the manuscript (JWJ, TIK); critical revision of the manuscript (JWJ, EKK, KYS, TIK); statistical expertise (JWJ); administrative, technical, or material support (SHH); supervision (TIK)

Correspondence: Tae-im Kim, MD, PhD, Department of Ophthalmology, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul, South Korea, 120-752. E-mail: tikim@yuhs.ac

Received: December 29, 2014
Accepted: April 15, 2015

Abstract

PURPOSE:

To compare the measurements of refractive errors and ocular aberrations obtained using iDesign and WaveScan (Abbott Medical Optics, Inc., Santa Ana, CA), and to compare surgical outcomes of wavefront-guided LASEK using ablation profiles based on both aberrometers.

METHODS:

Ninety myopic eyes of 45 normal patients were evaluated using both the iDesign and WaveScan to measure spherical and cylindrical errors, spherical equivalents, and Zernike coefficients of ocular aberrations. Wavefront-guided LASEK was performed in a different group of 59 eyes of 30 patients divided into two groups, the iDesign and Wavescan groups. The clinical outcomes between the two groups including uncorrected visual acuity, refractive errors, contrast sensitivity, and ocular aberration were compared at 1, 3, and 6 months postoperatively.

RESULTS:

The iDesign produced significantly higher myopic values for refractive errors than the WaveScan, as well as significantly lower levels of total higher order, third, fourth, and fifth order root mean square values and Zernike coefficients of vertical coma and spherical aberration. At postoperative 1, 3, and 6 months, there were no statistically significant differences between the two groups in terms of uncorrected visual acuity and remaining refractive errors. The percentages of patients with spherical equivalents within ±1.00 and ±0.50 diopters of emmetropia were 100% (29 eyes) and 75.9% (22 eyes), respectively, in the iDesign group and 96.7% (29 eyes) and 70.0% (21 eyes), respectively, in the WaveScan group. Mesopic contrast sensitivity values were significantly higher, and the change in root mean square values for spherical aberration was significantly lower in the iDesign group.

CONCLUSIONS:

There were significant differences between the iDesign and the WaveScan in the measurements of refraction and ocular aberrations. Wavefront-guided LASEK based on an ablation profile from the iDesign demonstrated comparable refractive predictability with the WaveScan group, resulting in minimal physician adjustment and superior postoperative visual quality.

[J Refract Surg. 2015;31(6):398–405.]

From the Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea (JWJ, BHC, SHH, EKK, KYS, TIK); the Department of Ophthalmology and Inha Vision Science Laboratory, Inha University School of Medicine, Incheon, South Korea (JWJ); and the Corneal Dystrophy Research Institute, Severance Biomedical Science Institute, and Brain Korea 21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea (EKK).

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

Supported in part by a grant from the Korean Health Technology R & D Project, Ministry of Health & Welfare, Republic of Korea (HI14C2044) and the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science, and Technology (2013R1A1A2058907).

AUTHOR CONTRIBUTIONS

Study concept and design (JWJ, TIK); data collection (JWJ, BHC); analysis and interpretation of data (JWJ, EKK, KYS, TIK); writing the manuscript (JWJ, TIK); critical revision of the manuscript (JWJ, EKK, KYS, TIK); statistical expertise (JWJ); administrative, technical, or material support (SHH); supervision (TIK)

Correspondence: Tae-im Kim, MD, PhD, Department of Ophthalmology, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul, South Korea, 120-752. E-mail: tikim@yuhs.ac

Received: December 29, 2014
Accepted: April 15, 2015

There have been several studies involving changes in aberrations after corneal refractive surgery.1–6 Poor surgical outcomes are often associated with postoperatively increased aberrations, mainly HOAs, which compromise patient satisfaction.1,6 Thus, accurate measurement and elimination of ocular aberrations, including HOAs, are important to yield superior visual outcome after refractive surgery. In this regard, several studies have compared wavefront-guided refractive surgery with conventional treatments and demonstrated that wavefront-guided customized ablation significantly reduced HOAs.7–9

It is critical to objectively evaluate all aberrations in the eyes preoperatively. With several technological developments, more precise measurements and better surgical corrections by wavefront-based refractive surgery have been achieved. These include improvements in the accuracy and resolution of wavefront sensors, increases in the sampling capability, and development of novel mathematical approaches for wavefront data reconstruction.10,11 The recently introduced Hartmann-Shack aberrometer, iDesign Advanced WaveScan aberrometer (Abbott Medical Optics, Inc., Santa Ana, CA), provides resolution five times greater than that of the WaveScan, a previous version of the aberrometer from the same manufacturer. The iDesign Advanced WaveScan aberrometer captures approximately 1,257 data points from a 7.0-mm pupil compared to the WaveScan, which captures 240 data points. Recently, Schallhorn et al.12 reported promising postoperative outcomes of wavefront-guided myopic LASIK using the iDesign aberrometer.

The purpose of this study was to compare the measurements of refractive errors and ocular aberrations using the iDesign Advanced WaveScan aberrometer and WaveScan. Also, the clinical data after wavefront-guided LASEK using ablation profiles based on the iDesign and the WaveScan were collected for comparative analysis.

Patients and Methods

This study was prospectively conducted on a total of 90 myopic eyes from 45 normal patients. Both the iDesign and WaveScan were used to obtain measurements on all eyes. None of the patients had any history of ocular disease, previous ocular surgery, or general disorders that affected the cornea. This study was approved by the Severance Hospital Institutional Review Board, Seoul, South Korea, and adhered to the tenets of the Declaration of Helsinki.

Measurements included spherical errors, cylindrical errors, spherical equivalents, and Zernike coefficients up to the sixth order. The wavefront across the entire pupil diameter was measured in the natural scotopic pupil condition and the data were then recalculated to a 4-mm pupil, using the device-incorporated software.13 The normalized Zernike coefficients were also used to calculate the root mean square (RMS) of HOAs (third to sixth order), and Zernike coefficients of trefoil-y (Z3−3), vertical coma (Z3−1), horizontal coma (Z31), trefoil-x (Z33), and spherical aberration (Z40) were determined.

The second part of this study consisted of performing wavefront-guided myopic LASEK in a different group of 59 eyes of 30 patients divided into two groups: the iDesign and the WaveScan group. Randomization was performed according to a computer-generated randomization schedule that assigned the patients to receive wavefront-guided LASEK using ablation profiles based on either iDesign or WaveScan. The wavefront data of 29 eyes from 15 patients obtained using the iDesign aberrometer were assigned to the iDesign group. The operations were performed according to the device’s own ablation profile with only the manufacturer’s suggested nomogram adjustment of spherical errors based on the amount of astigmatism as developed from previous studies of LASIK.12 The 30 eyes (15 patients) in the WaveScan group used wavefront data obtained using the WaveScan. The surgery was performed using a physician’s nomogram with adjustment of both spherical and cylindrical errors considering the manifested refraction and refractive errors of the WaveScan. Pre-operative examinations were performed, including slit-lamp microscopy, manifested, cycloplegic, and postcycloplegic manifested refractions, and uncorrected and corrected distance visual acuity (UDVA and CDVA). Postoperative visual and refractive outcomes of patients who underwent wavefront-guided LASEK were compared between the iDesign and WaveScan groups at 1-, 3-, and 6-month intervals postoperatively. Postoperative contrast sensitivity and ocular aberrations were evaluated at 6 months. The contrast sensitivity was measured after surgery using an Optec 6500 test system (Stereo Optical Co., Inc., Chicago, IL) at photopic (target illumination, 85 cd/m2) and mesopic (3.0 cd/m2) levels with or without glare. For control measurement of ocular aberrations after surgery in the iDesign and WaveScan groups, the iTrace ray-tracing type aberrometer (Tracey Technology, Houston, TX), which had a different mechanism from that of the iDesign and WaveScan systems, was used. Ocular aberrations were measured with a pupil dilated to larger than 6 mm in diameter induced by topical installation of one drop of 2.5% phenylephrine hydrochloride and 1% tropicamide (Mydrin-P; Pharmaceutical Co., Ltd., Osaka, Japan). Measurements were repeated at least three times and the best scan was chosen for the final analysis. The iTrace displayed entire ocular aberrations in RMS values automatically.

Wavefront-Guided LASEK Procedure

The wavefront-guided LASEK procedure was performed under topical anesthesia by a single surgeon (TIK). A speculum was used and, after pre-incision of the corneal epithelium using a special microtrephine with an 8.0-mm diameter blade (J 2900S; Janach, Como, Italy), an alcohol solution cone (J 2905; Janach) with a 8.5-mm diameter was placed on the cornea. Then, 20% ethanol was applied for 30 seconds and carefully washed off with ophthalmic balanced salt solution. The epithelium was detached as a single sheet upward toward the 12-o’clock position using a spatula. Wavefront-guided excimer laser ablation was performed using the Star S4 IR Laser System with iris registration (Abbott Medical Optics, Inc.). The following operative parameters were used: emission wavelength 193 nm, energy fluency 160 mJ/cm2, and repetition rate 10 Hz. For all treatments, the optical zone diameter was 6.0 mm with a transition zone of 8.00 mm. After ablation, the ablated corneal bed was irrigated with chilled balanced salt solution, the epithelium was then carefully repositioned with a spatula (J 2920A; Janach), and a therapeutic soft contact lens was placed on the cornea. Topical moxifloxacin (Vigamox; Alcon Laboratories, Inc., Fort Worth, TX) and 0.1% fluorometholone (Ocumetholone; Samil Pharmaceutical Co., Seoul, South Korea) were prescribed four times a day for 4 weeks, and then tapered.

Statistical Analysis

To compare measurements of refractive errors and ocular aberrations between the two devices, the paired t test was used. The relationship between the difference in measurements of the two study groups and the mean measurement of the devices was evaluated using linear regression analysis. A scatter plot showing the differences between two measurements against their average was used as described by Bland and Altman.14 For analysis of surgical outcomes, intergroup comparisons were performed using the Mann–Whitney test for continuous variables and comparisons between the preoperative and postoperative data were analyzed by Wilcoxon rank sum tests. Statistical analyses were performed using the SPSS statistical software package (version 20.0; SPSS Inc., Chicago, IL) and P values less than .05 were considered statistically significant.

Results

Comparison of Measurements Using iDesign and WaveScan

A total of 90 eyes of 45 patients (22 men and 23 women) were included. The mean age of the patients was 26 ± 6 years (range: 19 to 44 years). The mean spherical equivalents were −4.84 ± 2.77 diopters (D) with the iDesign and −4.45 ± 2.61 D with the WaveScan.

Table 1 shows the mean refractive errors, the corresponding ranges (minimum, maximum) obtained by the iDesign and WaveScan, and the mean difference between the two devices in terms of spherical and cylindrical errors and spherical equivalents. The iDesign tended to generate higher myopic values than the WaveScan. The paired t test revealed significant differences between spherical errors and spherical equivalents obtained by the iDesign and WaveScan.

Comparisons of Refractive Error Measurements Using iDesign and WaveScan in 90 Eyes of 45 Normal Subjects

Table 1:

Comparisons of Refractive Error Measurements Using iDesign and WaveScan in 90 Eyes of 45 Normal Subjects

Bland–Altman plots were used to assess the agreement of the measured refractive errors between the iDesign and the WaveScan groups, shown in Figure 1. Inspection of the plots revealed that there were correlations between measurements obtained by the two instruments. The limits of agreement range (95% confidence interval) of the mean measurements between the two devices were 1.64 D (sphere), 1.52 D (cylinder), and 1.87 D (spherical equivalent). Additionally, significant increase of positive correlations in refractive errors were observed in the iDesign compared to the WaveScan (P < .05). In agreement with the increase of refractive errors, the linear regression analysis showed that the iDesign measurements tended to be higher than those of the WaveScan.

A scatter plot showing the differences between two measurements of refractive errors against their average was used, as described by Bland and Altman.14 The coefficient of determination (r2) and probability of linear correlation (P value) are shown. The iDesign and WaveScan are manufactured by Abbott Medical Optics, Inc., Santa Ana, CA. D = diopters; SE = spherical equivalent

Figure 1.

A scatter plot showing the differences between two measurements of refractive errors against their average was used, as described by Bland and Altman.14 The coefficient of determination (r2) and probability of linear correlation (P value) are shown. The iDesign and WaveScan are manufactured by Abbott Medical Optics, Inc., Santa Ana, CA. D = diopters; SE = spherical equivalent

The comparison of measurements for ocular aberrations using iDesign and WaveScan is shown in Table 2. Compared to the WaveScan, the iDesign showed significantly lower measurements for RMS of total HOA (P < .001), third order (P < .001), fourth order (P < .001), fifth order (P = .003), Zernike coefficients of vertical coma (P < .001), and spherical (P < .001) aberration.

Comparisons of RMS Values (µm) for Ocular Aberration Using iDesign and WaveScan in 90 Eyes of 45 Normal Subjects

Table 2:

Comparisons of RMS Values (µm) for Ocular Aberration Using iDesign and WaveScan in 90 Eyes of 45 Normal Subjects

Clinical Outcomes of Wavefront-Guided LASEK Using iDesign and WaveScan

Fifty-nine eyes of 30 patients underwent wavefront-guided LASEK. The iDesign group included 29 eyes of 15 patients and the WaveScan group included 30 eyes of 15 patients. There were no postoperative complications such as severe corneal haze, delayed corneal wound healing, and postoperative infection in either group. In terms of the preoperative values, such as age, sex, and preoperative visual acuity or refractive errors except for cylindrical errors, no statistically significant differences were found between the two groups (Table 3). Although the patients were randomized into two groups, preoperative mean cylindrical error in the iDesign group (−1.92 ± 0.89 D) was significantly higher than in the WaveScan group (−1.29 ± 0.80 D).

Preoperative Characteristics and Postoperative Visual and Refractive Outcomes of Patients Who Underwent Wavefront-Guided LASEK for the iDesign and the WaveScan Groupsa

Table 3:

Preoperative Characteristics and Postoperative Visual and Refractive Outcomes of Patients Who Underwent Wavefront-Guided LASEK for the iDesign and the WaveScan Groups

Dramatic improvements in UDVA with reduction of refractive errors were observed at postoperative 1, 3, and 6 months in both groups when compared with the preoperative data (P < .001). Six months postoperatively, the number of eyes that achieved 20/20 was 28 eyes (96.6%) in the iDesign group and 28 eyes (93.3%) in the WaveScan group. All of the patients in both groups achieved 20/25 UDVA. There were no eyes that lost one or more lines of CDVA. The percentages of patients that gained one or more lines of CDVA were 3.4% and 3.3%, respectively (1 eye), in the iDesign and WaveScan groups. At 1, 3, and 6 months postoperatively there were no statistically significant differences in the UDVA or remaining refractive errors between the two groups. Although the patients in the iDesign group had higher preoperative cylindrical error, the postoperative cylindrical errors were not significantly different between the two groups (Table 3).

Figure 2 shows the achieved spherical equivalent correction against the intended correction. The percentages of patients with spherical equivalents within ±1.00 and ±0.50 diopters of emmetropia were 100% (29 eyes) and 75.9% (22 eyes), respectively, in the iDesign group and 96.7% (29 eyes) and 70.0% (21 eyes), respectively, in the WaveScan group. At postoperative 6 months, the frequency of astigmatism 1.00 D or less was 93.1% in the iDesign group and 96.6% in the WaveScan group. No statistical significance was observed (Pearson’s chi-square test, P > .050).

Scattergram showing the relationship between the achieved postoperative spherical equivalent corrections at postoperative 6 months, and the intended corrections. The iDesign and WaveScan are manufactured by Abbott Medical Optics, Inc., Santa Ana, CA. D = diopters

Figure 2.

Scattergram showing the relationship between the achieved postoperative spherical equivalent corrections at postoperative 6 months, and the intended corrections. The iDesign and WaveScan are manufactured by Abbott Medical Optics, Inc., Santa Ana, CA. D = diopters

Under photopic and mesopic conditions with or without glare, the iDesign group showed better contrast sensitivity than the WaveScan group. This was especially profound under mesopic conditions, with contrast sensitivity values significantly higher in the iDesign group in the spatial frequency of 3 cycles/ degree without glare and 6 cycles/degree with glare (P = .047 and .023, respectively; Figure 3).

Contrast sensitivity test values 3 months after wavefront-guided LASEK at (A) 85 cd/m2 photopic levels without glare, (B) photopic level with glare, (C) 3 cd/m2 mesopic level without glare, and (D) mesopic level with glare. The asterisks indicate statistically significant differences (P < .050) between groups. The iDesign and WaveScan are manufactured by Abbott Medical Optics, Inc., Santa Ana, CA.

Figure 3.

Contrast sensitivity test values 3 months after wavefront-guided LASEK at (A) 85 cd/m2 photopic levels without glare, (B) photopic level with glare, (C) 3 cd/m2 mesopic level without glare, and (D) mesopic level with glare. The asterisks indicate statistically significant differences (P < .050) between groups. The iDesign and WaveScan are manufactured by Abbott Medical Optics, Inc., Santa Ana, CA.

In the iDesign group, the RMS values of total HOAs, coma aberration, spherical aberration, secondary astigmatism, and trefoil significantly increased after surgery. In the WaveScan group, the RMS values of ocular aberrations excluding coma aberration significantly increased after surgery (Table 4). However, intergroup comparison of changes in entire ocular aberration was performed, and the change in RMS values for spherical aberration was significantly lower in the iDesign group (Figure 4).

Preoperative and Postoperative Ocular Aberrations of Patients Who Underwent Wavefront-Guided LASEK for the iDesign and WaveScan Groups

Table 4:

Preoperative and Postoperative Ocular Aberrations of Patients Who Underwent Wavefront-Guided LASEK for the iDesign and WaveScan Groups

Comparison of changes in ocular higher-order aberrations (HOA) before and after wavefront-guided LASEK. The asterisks indicate statistically significant differences (P < .050) between groups. The iDesign and WaveScan are manufactured by Abbott Medical Optics, Inc., Santa Ana, CA. RMS = root mean square

Figure 4.

Comparison of changes in ocular higher-order aberrations (HOA) before and after wavefront-guided LASEK. The asterisks indicate statistically significant differences (P < .050) between groups. The iDesign and WaveScan are manufactured by Abbott Medical Optics, Inc., Santa Ana, CA. RMS = root mean square

Discussion

This study was conducted to compare the efficacy of the iDesign and the WaveScan in terms of measurements of refractive errors and ocular aberrations and surgical outcomes using ablation profile of both machines. The iDesign showed higher myopic values than the WaveScan, and there was a correlation between the refractive errors of the two systems, with significant differences in values. Because the chromatic aberration was also considered in the iDesign, higher values of refractive errors were obtained in the iDesign group compared to the WaveScan group. A previous study15 reported that the refractions of the iDesign, which used video fixation target and comprehensive fogging sequence, were more reproducible than manifested refraction. In this study, the ocular aberrations measured using the iDesign were significantly lower than those measured by the WaveScan. Fadlallah et al.16 revealed that there were significant discrepancies in refractions and lower and higher order aberrations between the two devices, similar to our results.

Preoperative accurate evaluation that reflects all ocular aberrations is important for wavefront-based refractive surgery, creating a need for technological developments to produce satisfactory postoperative results. There is no current standard for wavefront aberrometers, and the measurements from various types of aberrometers are not interchangeable.17 Hartmann-Shack aberrometers have used a narrow laser beam that projects into the eye.18 After reflection from the retina, the light that passes through the pupil is guided through a set of relay lenses that splits the wavefront into individually focused spots onto a lenslet array, which breaks the beam of light into many beams focused onto a charged coupled device.19–21 The iDesign, a new Hartmann-Shack aberrometer, captures more data points than previous sensors (an average 1,257 data points from a 7.0-mm pupil) and analyzes the aberration data using Fourier reconstruction algorithms. It has a high-definition wavefront sensor that shows a resolution five times higher than the WaveScan. Owing to such technological developments, we hypothesized that significant differences between the two devices could be observed.

We compared the surgical outcomes of wavefront-guided LASEK between the iDesign and WaveScan groups to evaluate the effects of technological improvements on postoperative results of refractive surgery. In the iDesign group, the predictability of refractive errors was comparable to that of the WaveScan group because all patients were within 1.00 D of the target. Recently, Schallhorn et al.12 reported similar results showing good postoperative outcomes of myopic wavefront-guided LASIK using the iDesign. They found good refractive predictability, good cylinder correction, a high level of achieved UDVA, and good patient reported satisfaction. They attributed the greater precision of the iDesign for measurement of aberrations, including astigmatism, to the fourfold increase of lenslets in the device and the improved internal software. The enhanced iris registration system improved rotational and directional alignment of the ablation profile and astigmatism outcomes. Therefore, their results and ours suggest that wavefront-guided refractive surgery using the iDesign profile provides satisfactory surgical outcomes. Based on our previous surgical experiences of WaveScan refractive surgery, adjustment with a surgeon-based nomogram is required. However, the iDesign instructions recommended adhering to the manufacturer’s nomogram instead of surgeon-based adjustments for better surgical outcomes. This study confirmed that the manufacturer’s nomogram based on the iDesign shows comparable or better results without adjustment.

Previous studies indicated that poor postoperative outcomes were often associated with increased HOAs after refractive surgery.1,6 The aberrometric outcome after wavefront-guided myopic LASIK using the iDesign demonstrated a minimal induction of HOAs regardless of achieved myopic correction or preoperative aberrations.22 We compared the changes in ocular aberrations between the two groups using a ray-tracing type aber-rometer, the iTrace, which has a different mechanism from the iDesign and WaveScan systems. The increase of spherical aberration after wavefront-guided LASEK in the iDesign group was less than that in the WaveScan group. These results might be associated with greater precision when measuring and correcting aberrations and with the enhanced iris registration system, because even small rotational misalignments could affect the residual HOAs.23 Contrast sensitivity was also thought to be related to coma, spherical aberration, and total HOAs after refractive surgery.1,24 Our results showed better contrast sensitivity in mesopic conditions with less increase of spherical aberration in the iDesign group.

One limitation of this study was the relatively small number of cases. However, this is the first report comparing clinical outcomes after wavefront-guided LASEK using the new aberrometer with those using the previous version of the device.

The results showed significant differences in the measurements of refraction and ocular aberrations obtained by the iDesign and WaveScan. Wavefront-guided LASEK using a new aberrometer, the iDesign, showed good refractive predictability with minimal physician adjustment. The iDesign particularly improved postoperative visual qualities, such as contrast sensitivity and ocular aberration. Significant differences in measurements between the two devices appeared to be attributable to the technological advancement of providing optimal measurement for refractive surgery, and the iDesign showed promising outcomes following wavefront-guided LASEK.

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Comparisons of Refractive Error Measurements Using iDesign and WaveScan in 90 Eyes of 45 Normal Subjects

ParameteriDesignWaveScanMean Difference ± SD (iDesign – WaveScan)Pa


Mean ± SDRangeMean ± SDRange
Sphere (D)−4.15 ± 2.45−9.65 to −0.90−3.81 ± 2.32−8.57 to −0.24−0.42 ± 0.41< .001
Cylinder (D)−1.38 ± 1.01−4.78 to −0.07−1.28 ± 0.87−3.93 to −0.18−0.10 ± 0.38.021
Spherical equivalent (D)−4.84 ± 2.77−11.04 to −0.41−4.45 ± 2.61−10.13 to −0.61−0.47 ± 0.45< .001

Comparisons of RMS Values (µm) for Ocular Aberration Using iDesign and WaveScan in 90 Eyes of 45 Normal Subjects

Zernike Coefficient (µm)iDesign (Mean ± SD)WaveScan (Mean ± SD)Pa
Higher order RMS0.137 ± 0.0750.411 ± 0.166< .001
Third order RMS0.121 ± 0.0730.305 ± 0.159< .001
Fourth order RMS0.058 ± 0.0330.213 ± 0.126< .001
Fifth order RMS0.010 ± 0.0080.085 ± 0.051.003
Sixth order RMS0.005 ± 0.0040.073 ± 0.043.627
Trefoil-y (Z3−3)−0.017 ± 0.063−0.031 ± 0.126.295
Vertical coma (Z3−1)0.033 ± 0.0950.109 ± 0.224< .001
Horizontal coma (Z31)−0.003 ± 0.061−0.031 ± 0.170.102
Trefoil-x (Z33)−0.001 ± 0.045−0.003 ± 0.106.839
Spherical aberration (Z40)0.033 ± 0.0360.143 ± 0.153< .001

Preoperative Characteristics and Postoperative Visual and Refractive Outcomes of Patients Who Underwent Wavefront-Guided LASEK for the iDesign and the WaveScan Groupsa

ParameteriDesign GroupWaveScan GroupP
No. of eyes2930
Sex (M:F)10:511:4
Age (range) (years)23.9 ± 3.9 (20 to 32)23.7 ± 3.5 (19 to 30).823b
Preoperative data
  UCVA (logMAR)0.90 ± 0.401.03 ± 0.35.413c
  CDVA (logMAR)0.02 ± 0.020.02 ± 0.05.354c
  Sphere (D)−4.92 ± 2.00−5.07 ± 1.58.747
  Cylinder (D)−1.92 ± 0.89−1.29 ± 0.80.023
  Spherical equivalent (D)−5.90 ± 1.77−5.67 ± 1.82.627
Postoperative data
  1M UCVA (logMAR)0.08 ± 0.060.04 ± 0.06.051c
  1M sphere (D)−0.41 ± 0.92−0.24 ± 0.64.420
  1M cylinder (D)−0.76 ± 0.42−0.84 ± 0.54.842
  1M spherical equivalent (D)−0.81 ± 0.92−0.64 ± 0.73.529
  3M UCVA (logMAR)0.02 ± 0.030.01 ± 0.03.459b
  3M CDVA (logMAR)0.01 ± 0.020.01 ± 0.03.521b
  3M sphere (D)−0.05 ± 0.580.00 ± 0.50.777
  3M cylinder (D)−0.45 ± 0.37−0.46 ± 0.30.900
  3M spherical equivalent (D)−0.27 ± 0.56−0.23 ± 0.52.804
  6M UCVA (logMAR)0.00 ± 0.010.01 ± 0.02.795c
  6M CDVA (logMAR)0.00 ± 0.010.01 ± 0.02.795c
  6M sphere (D)0.14 ± 0.48−0.03 ± 0.54.217
  6M cylinder (D)−0.53 ± 0.47−0.31 ± 0.36.058
  6M spherical equivalent (D)−0.15 ± 0.49−0.17 ± 0.48.843

Preoperative and Postoperative Ocular Aberrations of Patients Who Underwent Wavefront-Guided LASEK for the iDesign and WaveScan Groups

Ocular Aberration (RMS, µm)iDesign GroupWaveScan Group


PreoperativePostoperativePaPreoperativePostoperativePa
Total HOAs0.495 ± 0.0370.686 ± 0.061.0040.479 ± 0.0280.674 ± 0.039.001
Coma aberration0.264 ± 0.0290.433 ± 0.064.0040.328 ± 0.0390.437 ± 0.049.083
Spherical aberration0.058 ± 0.0130.146 ± 0.061< .0010.081 ± 0.0070.283 ± 0.016< .001
Secondary astigmatism0.112 ± 0.0160.269 ± 0.061< .0010.105 ± 0.0090.199 ± 0.025< .001
Trefoil0.190 ± 0.0120.307 ± 0.028.0010.229 ± 0.0080.267 ± 0.006< .001

10.3928/1081597X-20150521-06

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