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Kim and Chung: Comparison of Corneal Curvatures Obtained with Different Devices
Original Article
Journal of the Korean Ophthalmological Society

Journal of the Korean Ophthalmological Society 2012; 53(5): 618-625.

Published online: 16 May 2012

DOI: https://doi.org/10.3341/jkos.2012.53.5.618

Comparison of Corneal Curvatures Obtained with Different Devices

Soyoon Kim, MD, Sung Kun Chung, MD, PhD

Department of Ophthalmology and Visual Science, Yeouido St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Korea.

Address reprint requests to Sung Kun Chung, MD, PhD. Department of Ophthalmology, The Catholic University of Korea, Yeouido St. Mary's Hospital, #63-ro 10, Yeongdeungpo-gu, Seoul 150-713, Korea. Tel: 82-2-3779-1150, Fax: 82-2-761-6869, eyedoc@catholic.ac.kr

Received 12 August 2011       Accepted 24 March 2012

Copyright © 2012 The Korean Ophthalmological Society

Abstract

Purpose

To evaluate device efficacy using the corneal curvature value.

Methods

Prospectively, 35 patients (70 eyes) were enrolled in the present study. Three sets of corneal curvature values were obtained using the autorefractor (RK-F1®), manual keratometer (OM-2®), partial coherence interferometry keratometer (IOL Master®), wavefront analyzer (KR-1W®), and videokeratography (Orbscan II®). Repeatability of each device was evaluated by coefficient of variation, standard deviation, and intraclass correlation coefficient. RM-ANOVA on ranks was used to compare the differences in corneal curvatures among the devices. The Bland-Altman plot was performed to assess measurement agreement among the devices.

Results

The coefficient of variation values from each device ranged from 2.92% (IOL master®) to 3.06% (Orbscan II®), and the values of intraclass correlation coefficient ranged from 0.965 (KR-1W®) to 0.997 (IOL master®). Compared with the manual keratometer, there was a maximum corneal curvature difference of 1.23 D in KR-1W®, while the other devices had differences less than 0.82 D.

Conclusions

When assessing corneal curvature, the repeatability values were similar among the 5 devices, although a difference greater than 1 D was observed when comparing the KR-1W® to the manual keratometer.

Keywords: Corneal curvature, Keratometry

Figures and Tables

Figure 1
Bland-Altman plots showing differences in corneal curvature measurements between devices. The upper and lower dashed lines indicate 95% limits of agreement and the solid line indicates the mean.
jkos-53-618-g001
Table 1
Results for repeatability of seven corneal curvature measurements by coefficient of variation, standard deviation, and intraclass correlation coefficient
jkos-53-618-i001

CV = coefficient of variation; D = diopters; ICC = intraclass correlation coefficient; SD = standard deviation

Table 2
Results for the comparison of the 6 corneal curvature measurements among devices
jkos-53-618-i002

The mean difference, SD, upper LoA, lower LoA, RM-ANOVA on Ranks are displayed for each pair of devices.

D = diopters; SD = standard deviation; LoA = 95% limits of agreement; RM-ANOVA on Ranks = repeated measures analysis of variance on ranks; 15 comparisons were made for each device pair (3 measurements each).

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