Journal of Refractive Surgery

Original Article Supplemental Data

Repeatability, Reproducibility, and Agreement of Two Scheimpflug-Placido Anterior Corneal Analyzers for Posterior Corneal Surface Measurement

Fangjun Bao, MD; Giacomo Savini, MD; Bao Shu, MD; Senmiao Zhu, MD; Rongrong Gao, MD; Guanxin Dang, MD; Ayong Yu, MD, PhD; Qinmei Wang, MD; Jinhai Huang, MD

Abstract

PURPOSE:

To evaluate the intraoperator repeatability and interoperator reproducibility of two Scheimpflug-Placido anterior corneal analyzers (Sirius; Costruzione Strumenti Oftalmici, Florence, Italy, and TMS-5; Tomey, Nagoya, Japan) for the measurement of posterior corneal surface in normal eyes and the agreement between the two devices.

METHODS:

The current prospective study investigated 55 right eyes of 55 healthy patients in a random order. The posterior steep keratometry (Ks), flat keratometry (Kf), mean keratometry (Km), and astigmatism were randomly measured by two independent experienced operators using the Sirius and TMS-5 Scheimpflug-Placido systems. Three consecutive measurements were obtained. Vector analysis was used for astigmatism. To assess intraoperator repeatability and interoperator reproducibility, within-subject standard deviation (Sw) and test–retest repeatability (TRT, 2.77 Sw) were calculated. The Bland–Altman plots and 95% limits of agreement (LoA) were used to evaluate the agreement between the two systems.

RESULTS:

In the Sirius Scheimpflug-Placido system, the Sw and TRT of keratometry and astigmatism were less than 0.04 and 0.12 diopters (D), respectively. The interoperator Sw and TRT were less than 0.03 and 0.07 D, respectively. In the TMS-5 Scheimpflug-Placido system, the intraoperator Sw and TRT did not exceed 0.03 and 0.08 D, respectively. The interoperator Sw and TRT were no greater than 0.02 and 0.05 D, respectively. All parameters showed minor fluctuations in the 95% LoA.

CONCLUSIONS:

Both Scheimpflug-Placido systems show high repeatability and reproducibility for posterior corneal surface measurement. A high concordance between the two devices suggests interchangeable use in normal eyes.

[J Refract Surg. 2017;33(8):524–530.]

Abstract

PURPOSE:

To evaluate the intraoperator repeatability and interoperator reproducibility of two Scheimpflug-Placido anterior corneal analyzers (Sirius; Costruzione Strumenti Oftalmici, Florence, Italy, and TMS-5; Tomey, Nagoya, Japan) for the measurement of posterior corneal surface in normal eyes and the agreement between the two devices.

METHODS:

The current prospective study investigated 55 right eyes of 55 healthy patients in a random order. The posterior steep keratometry (Ks), flat keratometry (Kf), mean keratometry (Km), and astigmatism were randomly measured by two independent experienced operators using the Sirius and TMS-5 Scheimpflug-Placido systems. Three consecutive measurements were obtained. Vector analysis was used for astigmatism. To assess intraoperator repeatability and interoperator reproducibility, within-subject standard deviation (Sw) and test–retest repeatability (TRT, 2.77 Sw) were calculated. The Bland–Altman plots and 95% limits of agreement (LoA) were used to evaluate the agreement between the two systems.

RESULTS:

In the Sirius Scheimpflug-Placido system, the Sw and TRT of keratometry and astigmatism were less than 0.04 and 0.12 diopters (D), respectively. The interoperator Sw and TRT were less than 0.03 and 0.07 D, respectively. In the TMS-5 Scheimpflug-Placido system, the intraoperator Sw and TRT did not exceed 0.03 and 0.08 D, respectively. The interoperator Sw and TRT were no greater than 0.02 and 0.05 D, respectively. All parameters showed minor fluctuations in the 95% LoA.

CONCLUSIONS:

Both Scheimpflug-Placido systems show high repeatability and reproducibility for posterior corneal surface measurement. A high concordance between the two devices suggests interchangeable use in normal eyes.

[J Refract Surg. 2017;33(8):524–530.]

The increasing popularity of cataract and intraocular lens (IOL) implantation and keratorefractive surgery1,2 has raised the expectations of optimal postoperative visual quality over the years, not only for corrected distance visual acuity, but also to facilitate routine and comfortable reading. Accurate measurement of corneal parameters plays an important role in detailed preoperative ocular examinations. Previous studies emphasized the role of anterior corneal surface while neglecting the posterior corneal surface, which also plays an indispensable role. Posterior corneal astigmatism has been shown to influence both magnitude and axis of total corneal astigmatism,3 and thus plays an important role in the calculation of toric intraocular lenses (IOLs).4 Moreover, the posterior corneal surface is a key factor for the detection of subclinical disorders such as forme fruste keratoconus and monitoring of corneal stability during follow-up.5,6 In recent years, several ophthalmic instruments have been used to measure the posterior corneal surface.

Technologies enabling the assessment of posterior corneal surface include scanning-slit corneal topography (Orbscan; Bausch & Lomb, Rochester, NY),7–9 optical coherence tomography, and Scheimpflug imaging. The latter technology has been adopted by the Pentacam (Oculus Optikgeräte, Wetzlar, Germany), a single rotating Scheimpflug camera; Sirius (Costruzione Strumenti Oftalmici, Florence, Italy) and TMS-5 (Tomey Corporation, Nagoya, Japan), both featuring a single rotating Scheimpflug system combined with a Placido disk corneal topographer; and the Galilei (Ziemer, Port, Switzerland), a dual Scheimpflug camera combined with a Placido disk corneal topographer.10

To our knowledge, there are no published studies comparing the posterior corneal surface measurements provided by the Sirius and TMS-5. Therefore, our study evaluated the intraoperator repeatability, interoperator reproducibility, and concordance of the two analyzers for posterior keratometry and astigmatism measurements, as well as their preferential use in clinical examinations.

Patients and Methods

Patients

Fifty-five right eyes of 55 healthy patients (20 men and 35 women) were analyzed in this prospective study. The mean age was 25 ± 1.61 years (range: 23 to 34 years). Patients were recruited at the Eye Hospital of Wenzhou Medical University in China. All participants underwent comprehensive ophthalmologic examination before the measurement. The exclusion criteria were: active ocular disease, corneal pathology or corneal scarring, previous ocular surgery or ocular trauma, a history of contact lens wearing (more than 4 weeks for rigid contact lens and 2 weeks for soft contact lens), intraocular pressure greater than 21 mm Hg, systemic disease (eg, autoimmune diseases and connective tissue diseases), and poor eye fixation. This study was approved by the Research Review Board of the Eye Hospital of Wenzhou Medical University. All patients were advised of the objectives and procedures of the study and all participants provided written informed consent. This study was conducted in accordance with the tenets of the Declaration of Helsinki and Good Clinical Practices.11

Instruments

The Sirius system consists of a 180° rotating Scheimpflug camera and a small-angle Placido disk corneal topographer (22 rings), which provide a full analysis of the anterior and posterior corneal surface within 12 mm. The 2-second scan using the Scheimpflug camera captures a series of 25 images with up to 25,000 points defining the anterior segment of the eye. Simultaneously, the Placido disk projects 22 rings to capture more than 30,000 points and defines the ring edges and slope. By merging the ring topography with the Scheimpflug tomography, the results of the anterior corneal segment are obtained.12,13

Similar to the Sirius system, the TMS-5 system includes a rotating Scheimpflug camera and a Placido disk corneal topographer (32 rings). However, the two parts of the TMS-5 system capture images separately. By aligning the reflection of the laser light on the center of the cornea mire ring automatically, the Placido topography completes a measurement with more than 7,300 data points collected. In the Scheimpflug pattern, the TMS-5 system captures no fewer than 40,960 data points to analyze the anterior and posterior corneal surfaces.14,15

Procedures

Two well-trained independent experienced operators (SB, GD) operated the instruments following the manufacturer's guidelines. Both examiners were blinded to the previous test results of each participant. All measurements were conducted between 10:00 AM and 5:00 PM to minimize the effect of diurnal fluctuation on corneal shape. To avoid any interference of the correlation between the eyes, only the right eye was analyzed, as previously done in other studies.16–18 Under natural pupil conditions, measurements were collected in a dim room within 30 minutes. Both devices were calibrated before commencing the prospective study.

All patients were examined with both devices. The measuring sequence was randomized according to a computer-generated random number sequence to avoid methodological bias. Patients were positioned on the chin rest and gate at an internal center fixation target with both eyes open. The examiner adjusted the joystick until a clear alignment along the visual axis was obtained. Each time before imaging, the patients were asked to blink completely to provide an optically smooth tear film over the cornea. After each measurement, patients were asked to sit back for 3 minutes. Only good quality images (with quality specification exceeding 90%) were collected for analysis. Data that failed to meet the requisite standards were deleted and additional scans were obtained. To assess the intraoperator repeatability, the measurements were repeated three times by each observer, consecutively. The interoperator reproducibility of each system was determined by averaging the values of three successive measurements. The difference in the mean values obtained by the two operators was used to assess interoperator reproducibility.

The following parameters of posterior corneal surface were recorded: keratometry in the flattest meridian (Kf), keratometry in the steepest meridian (Ks), mean keratometry (Km, which is equal to the average of Kf and Ks), and magnitude of astigmatism (ie, the dioptric difference between Ks and Kf without considering the axis orientation). To include the astigmatism axis, vector analysis was used to convert the sphere (S) and cylinder (C) notation into J0 and J45 power vectors. The equations are as follows: J0 = −C/2cos2α, J45 = −C/2sin2α, where α corresponds to the steep axis of the cylinder. In the Jackson cross cylinder, J0 refers to the cylinder axis at the 180° and 90° meridians, whereas the J45 refers to the cylinder axis at the 45° or 135° meridians.19 The J0 and J45 vectors from different patients are averaged to calculate the mean corneal astigmatism (magnitude and axis) using the formulae previously described by Thibos et al.19

Statistical Analysis

The SPSS software for Windows (version 21; IBM Corporation, Armonk, NY) was used for statistical analysis. Results were expressed as mean ± standard deviation. Normality of the data distribution was assessed by the Kolmogorov–Smirnov test. To evaluate the intraoperator repeatability and interoperator reproducibility, the within-subject standard deviation (Sw), and test–retest repeatability (TRT, 2.77 Sw) were calculated from consecutive measurements obtained by two operators.

The Sw, which is defined as the arithmetic square root of variance, reflects the discrete degree between individuals in the group. Sw is calculated as follows:

∑i=1N(ki−1)si2∑i=1Nki−N
where N is the total number of patients, i is the ith subject, k is the replicate measurement, and si, which corresponds to the ith subject, is computed from k. The TRT represents the 95% distribution range of differences between measurements.

The paired t test was used to compare the differences in posterior corneal parameter determined by the two instruments. A P value of less than .05 was considered statistically significant.20 Bland–Altman plots were used to assess the concordance between Sirius and TMS-5. The x axis represents the average values measured by the Sirius and TMS-5, whereas the y axis refers to the differences between them. The 95% limits of agreement (LoA) were evaluated by the mean difference ± 1.96 standard deviation of the difference, which defines the range within which 95% of the differences between measurements by the two devices are expected to lie.21

Results

Intraoperator Repeatability

Tables AB (available in the online version of this article) show the high intraoperator repeatability of both the Sirius and TMS-5 systems. The Sw and TRT for Kf and Ks were less than 0.03 and less than 0.09 D, respectively, with the Sirius. For astigmatism, the Sw was no more than 0.04 D and the TRT was no more than 0.12D. For J0 and J45, the Sw and TRT were less than 0.02 and 0.06 D, respectively. The TMS-5 analyzer showed a Sw and TRT for Kf and Ks within 0.02 and less than 0.06 D, respectively. The magnitude of astigmatism showed a Sw of no more than 0.03 D and the TRT was no greater than 0.08 D, respectively. For J0 and J45, the Sw and TRT were less than 0.02 and 0.05 D, respectively.

Intraobserver Repeatability of Posterior Corneal Surface Parameters Measured Using the Sirius Scheimpflug-Placido Analyzer

Table A:

Intraobserver Repeatability of Posterior Corneal Surface Parameters Measured Using the Sirius Scheimpflug-Placido Analyzer

Intraobserver Repeatability of Posterior Corneal Surface Parameters Measured Using the TMS-5 Scheimpflug-Placido Analyzer

Table B:

Intraobserver Repeatability of Posterior Corneal Surface Parameters Measured Using the TMS-5 Scheimpflug-Placido Analyzer

Interoperator Reproducibility

Tables CD (available in the online version of this article) display the interoperator reproducibility results of all parameters. Similar to the repeatability data, both the Sirius and TMS-5 showed excellent measurements. The Sw for Sirius and TMS-5 was within 0.03 and less than 0.02 D, respectively. The TRT for Sirius and TMS-5 was not greater than 0.07 and 0.05, respectively.

Interobserver Reproducibility of Posterior Corneal Surface Parameters Measured Using the Sirius Scheimpflug-Placido Analyzer

Table C:

Interobserver Reproducibility of Posterior Corneal Surface Parameters Measured Using the Sirius Scheimpflug-Placido Analyzer

Interobserver Reproducibility of Posterior Corneal Surface Parameters Measured Using the TMS-5 Scheimpflug-Placido Analyzer

Table D:

Interobserver Reproducibility of Posterior Corneal Surface Parameters Measured Using the TMS-5 Scheimpflug-Placido Analyzer

Sirius vs. TMS-5

The measurements obtained with both devices are compared in Table 1 and Figure 1. According to Table 1, except for the Ks, statistically significant differences were observed between the two Scheimpflug-Placido analyzers in terms of posterior corneal surface measurements. The Sirius yielded slightly lower values of Kf, Km, and J0 than the TMS-5, but slightly higher values for astigmatism and J45. The mean values for posterior corneal astigmatism were 0.38 D at 89° and 0.26 D at 91° for the Sirius and TMS-5, respectively. On average, the Sirius overestimated the posterior corneal astigmatism by 0.12 D at 86° with respect to the TMS-5. Figure 1 displays the Bland–Altman plots, with narrow 95% LoA, which indicate excellent concordance between these two devices.

Comparison of Posterior Corneal Surface Parameters Measured Using the Sirius and the TMS-5 Scheimpflug-Placido Analyzers

Table 1:

Comparison of Posterior Corneal Surface Parameters Measured Using the Sirius and the TMS-5 Scheimpflug-Placido Analyzers

Bland–Altman plots show agreement between the Sirius (Costruzione Strumenti Oftalmici, Florence, Italy) and the TMS-5 (Tomey, Nagoya, Japan) Scheimpflug-Placido analyzers for measurement of the posterior corneal dioptric power for (A) flattest meridian, (B) steepest meridian, (C) mean, (D) astigmatism vector J0, (E) astigmatism, and (F) astigmatism vector J45. The solid line indicates the mean difference (bias), and the dotted lines indicate the 95% limits of agreement. D = diopters

Figure 1.

Bland–Altman plots show agreement between the Sirius (Costruzione Strumenti Oftalmici, Florence, Italy) and the TMS-5 (Tomey, Nagoya, Japan) Scheimpflug-Placido analyzers for measurement of the posterior corneal dioptric power for (A) flattest meridian, (B) steepest meridian, (C) mean, (D) astigmatism vector J0, (E) astigmatism, and (F) astigmatism vector J45. The solid line indicates the mean difference (bias), and the dotted lines indicate the 95% limits of agreement. D = diopters

Discussion

In the current study, the posterior corneal refractive power measured by the Sirius and TMS-5 showed high repeatability and reproducibility. The Sw values were less than 0.04 D and the TRT values were within 0.09 D. Because the posterior corneal surface measurements were based on the Scheimpflug principle, the results were similar to those previously reported with other Scheimpflug systems.22,23

Using the Pentacam system for the posterior corneal surface in normal eyes, Piñero et al.23 reported that the TRT of the Kf and the Ks was not greater than 0.08 and 0.12 D, respectively, which suggested high precision. Miranda et al.24 found highly repeatable metrics derived from the corneal posterior surface over the tested timescales. Chen and Lam25 also showed high intraoperator reliability (intraclass correlation coefficient [ICC] ≥ 0.804), except for the posterior corneal power vector J45 (ICC = 0.742). The Galilei dual Scheimpflug analyzer was also investigated in previous studies. Güler et al.22 evaluated the posterior corneal power, posterior elevation, and eccentricity obtained by the Galilei and found a high level of repeatability and reproducibility in normal, keratoconic, and postrefractive corneas. Similar results were reported by Fahd et al.26 on posterior elevation and best-fit sphere.

Although only a few studies directly investigated the posterior corneal surface measurements obtained by the two devices used in our study, several researchers reported satisfactory repeatability and reproducibility of other corneal parameters. Huang et al.27 found excellent intraoperator repeatability and reproducibility of corneal thickness measurements used by the Sirius in post-LASIK eyes with a TRT of less than 0.7% and an ICC higher than 0.99. De la Parra-Colín et al.28 assessed six anterior segment biometry parameters in healthy patients and found that the Sirius presented high ICC and low coefficient of variation values. In a study of corneal curvature, minimal corneal thickness, and anterior chamber depth measurements assessment reported by Nasser et al.,29 the Sirius showed excellent repeatability with low coefficient of variation. However, the 95% LoA between the Sirius and Pentacam HR were wide, suggesting that the two devices may not be used interchangeably. Savini et al.30 found a TRT of 0.05 D for posterior corneal power in normal and post-LASIK eyes using the Sirius. The TMS-5 system also exhibited accuracy and precision in anterior corneal surface measurements. Guilbert et al.31 reported excellent repeatability for corneal thickness, keratometry, and anterior or posterior best-fit sphere measurements, all of which showed high ICC values exceeding 0.96. Huang et al.32 evaluated the central corneal thickness and thinnest corneal thickness measurements obtained from the TMS-5 and found high repeatability and reproducibility. The TRT was less than 19 µm and the ICC was greater than 0.90.

Agreement between the two devices was high, as shown by the narrow 95% LoAs, which were comparable to a previous study by Savini et al.14 Furthermore, although paired comparisons produced a statistically significant difference in Kf and Km, it was not clinically significant because it was lower than 0.25 D in 95% of cases.

Preexisting corneal astigmatism is routinely encountered in patients with cataract.33 Nearly 15% to 30% of patients with cataract manifest more than 1.50 D of corneal astigmatism, which has a significant effect on visual acuity if left uncorrected and leads to unsatisfactory postoperative visual outcomes.3 Posterior corneal astigmatism has been shown to influence total corneal astigmatism34,35 and cannot be neglected when planning toric IOLs implantation.3,4,36,37 In the current study, we used the Jackson vectors to analyze the posterior astigmatism. The Sw and TRT values acquired by the Sirius were less than 0.04 and 0.12 D, respectively, whereas those obtained by the TMS-5 were no greater than 0.03 and 0.08 D, respectively. Both showed excellent repeatability and reproducibility. On average, the Sirius yielded a slightly higher astigmatism than the TMS-5, but this difference (0.12 D @ 6°) was not clinically significant. Similarly, Lee et al.38 compared the corneal astigmatism measured by six instruments and found concordance between manual keratometry and Pentacam in polar value analysis.

The current study had several limitations. First, our sample was restricted to healthy patients, who are not representative of patients with corneal pathology, and post-LASIK patients or patients with keratoconus. Second, we evaluated the astigmatism-related parameters provided by the two devices and did not assess other values related to aberration and elevation. Third, the patient group in our study was a rather young population, whose age range may be extended in future studies. Finally, we analyzed only the right eye of each participant to avoid the correlation between fellow eyes and its influence on the statistical outcomes. This approach has been extensively adopted in the literature, but randomization might be a stronger tool to avoid biases from the correlation between fellow eyes.

The Sirius and TMS-5 systems showed high repeatability and reproducibility of the three consecutive measurements involving the posterior corneal surface. The narrow 95% LoA suggests a high degree of concordance, which indicates that the two devices may be used interchangeably in normal eyes.

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Comparison of Posterior Corneal Surface Parameters Measured Using the Sirius and the TMS-5 Scheimpflug-Placido Analyzers

ParameterMean Difference ± SDP95% LoA
Kf (D)−0.12 ± 0.06< .001−0.23 to 0.00
Ks (D)0.01 ± 0.04.213−0.08 to 0.10
Km (D)−0.06 ± 0.04< .001−0.14 to 0.03
Astigmatism0.13 ± 0.06< .0010.01 to 0.24
J0−0.06 ± 0.03< .001−0.12 to −0.01
J450.01 ± 0.03.027−0.05 to 0.07

Intraobserver Repeatability of Posterior Corneal Surface Parameters Measured Using the Sirius Scheimpflug-Placido Analyzer

ParameterObserverMean (D) ± SDSw (D)2.77 Sw (D)
Kf1st−6.39 ± 0.260.030.08
2nd−6.38 ± 0.260.030.09
Ks1st−6.00 ± 0.190.020.06
2nd−6.00 ± 0.190.020.06
Km1st−6.19 ± 0.220.010.04
2nd−6.19 ± 0.220.020.05
Astigmatism magnitude1st0.39 ± 0.120.040.11
2nd0.39 ± 0.120.040.12
J01st−0.19 ± 0.060.020.06
2nd−0.19 ± 0.060.020.06
J451st0.00 ± 0.040.020.06
2nd0.00 ± 0.040.020.05

Intraobserver Repeatability of Posterior Corneal Surface Parameters Measured Using the TMS-5 Scheimpflug-Placido Analyzer

ParameterObserverMean (D) ± SDSw (D)2.77 Sw (D)
Kf1st−6.27 ± 0.250.020.06
2nd−6.27 ± 0.250.020.05
Ks1st−6.01 ± 0.200.020.04
2nd−6.01 ± 0.200.020.05
Km1st−6.14 ± 0.220.010.04
2nd−6.14 ± 0.220.010.04
Astigmatism magnitude1st0.26 ± 0.090.030.08
2nd0.26 ± 0.090.020.07
J01st−0.13 ± 0.050.010.04
2nd−0.13 ± 0.050.020.05
J451st0.00 ± 0.030.020.05
2nd0.00 ± 0.030.010.04

Interobserver Reproducibility of Posterior Corneal Surface Parameters Measured Using the Sirius Scheimpflug-Placido Analyzer

ParameterMean (D) ± SDSw (D)2.77 Sw (D)
Kf−6.27 ± 0.910.020.06
Ks−5.89 ± 0.840.020.04
Km−6.08 ± 0.870.010.04
Astigmatism0.38 ± 0.120.030.07
J0−0.18 ± 0.070.010.04
J450.00 ± 0.040.020.04

Interobserver Reproducibility of Posterior Corneal Surface Parameters Measured Using the TMS-5 Scheimpflug-Placido Analyzer

ParameterMean (D) ± SDSw (D)2.77 Sw (D)
Kf−6.16 ± 0.890.020.05
Ks−5.90 ± 0.840.020.04
Km−6.03 ± 0.870.010.04
Astigmatism0.26 ± 0.090.020.05
J0−0.12 ± 0.050.010.03
J450.00 ± 0.030.010.03
Authors

From the School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China (FB, BS, SZ, RG, GD, AY, QW, JH); Key Laboratory of Vision Science, Ministry of Health P.R. China, Wenzhou, Zhejiang, China (FB, AY, QW, JH); and G.B. Bietti Foundation IRCCS, Rome, Italy (GS).

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

Drs. Wang and Huang contributed equally to this work and should be considered as equal corresponding authors.

Supported in part by the National Natural Science Foundation of China (81300807); Foundation of Wenzhou City Science & Technology Bureau (J20140014, Y20150076); Health Bureau of Zhejiang Province (2016RCB013); Zhejiang Provincial & Ministry of Health Research Fund For Medical Sciences (WKJ-ZJ-1530); and The National Key Research and Development Program of China (2016YFC0100200, 2016YFC0100201). The contribution of G.B. Bietti Foundation IRCCS was supported by the Italian Ministry of Health and Fondazione Roma.

AUTHOR CONTRIBUTIONS

Study concept and design (FB, QW, JH); data collection (BS, GD); analysis and interpretation of data (GS, SZ, RG, AY, JH); writing the manuscript (FB, GS, BS, QW, JH); critical revision of the manuscript (FB, GS, SZ, RG, GD, AY, QW, JH); statistical expertise (GS, JH); administrative, technical, or material support (AY, QW); supervision (JH)

Correspondence: Jinhai Huang, MD, Eye Hospital of Wenzhou Medical University, 270 West Xueyuan Road, Wenzhou, Zhejiang, 325027, China. E-mail: wqm6@mail.eye.acn.cn (Qinmei Wang) and vip999vip@163.com (Jinhai Huang)

Received: December 04, 2016
Accepted: May 16, 2017

10.3928/1081597X-20170606-01

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