Purpose: The aim of this study was to evaluate the repeatability of central corneal thickness (CCT) measurements in normal eyes using 2 new noncontact specular microscopes (NCSMs) EM-3000 (Tomey, Japan) and SP-02 (CSO, Italy) and to compare the results with those obtained from an SP-3000P NCSM (Topcon, Japan) and ultrasound pachymetry (USP).
Methods: Seventy subjects were enrolled in a prospective study. A single experienced ophthalmologist performed tests with each of the 4 instruments. Measurements were obtained in the right eye during the same session. The testing sequence of the NCSM was randomly selected. After performing noncontact examinations, the USP was performed to derive the CCT measurements. Intraoperator repeatability was analyzed using within-subject coefficient of variation and intraclass correlation coefficients. The agreement between NCSMs or NCSM and USP was assessed with Bland–Altman plots and 95% limits of agreement (LoA).
Results: The mean CCT values measured by SP-3000P, EM-3000, SP-02, and USP were 513.66 ± 33.14 μm, 529.12 ± 33.22 μm, 549.06 ± 40.27 μm, and 539.01 ± 35.73 μm, respectively. All coefficients of variation were <1.3%, and the intraclass correlation coefficients were >0.95. There were statistically significant differences between any 2 devices as determined by CCT measurements. The mean difference between paired comparisons was >9 μm. The 95% LoA ranges were broad, and the greatest 95% LoA was found to exist between SP-3000P and SP-02.
Conclusions: The new NCSMs and USP all show a high intraoperator repeatability for CCT measurements in normal eyes. However, interdevice agreement was poor and prevented the comparison of CCT measurements taken with different instruments.
*School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China;
†Key Laboratory of Vision Science, Ministry of Health PR China, Wenzhou, Zhejiang, China;
‡Hubei University of Medicine Affiliated Taihe Hospital, Shiyan, Hubei, China;
§G. B. Bietti Eye Foundation-IRCCS, Rome, Italy; and
¶Department of Ophthalmology, Zhongshan Hospital, Fudan University, Shanghai, China.
Reprints: Jinhai Huang, Eye Hospital of Wenzhou Medical University, 270 West Xueyuan Rd, Wenzhou, Zhejiang 325027, China (e-mail: firstname.lastname@example.org).
F. Bao and Q. Wang have contributed equally as first authors.
The authors have no conflicts of interest to disclose.
Supported in part by the Foundation of Wenzhou City Science and Technology Bureau (Y20110045, Y20120176); the Health Bureau of Zhejiang Province (2012KYB135); and the Scientific Research Fund of Zhejiang Provincial Education Department (Y201223147).
Received January 12, 2014
Accepted February 13, 2014