Repeatability, Reproducibility and Agreement of Central Corneal Thickness Measurements by Two Noncontact Pachymetry Devices

Abstract This study was designed to assess the repeatability, reproducibility, and agreement of Noncontact Pachymetry (NPC) (Topcan TRK-۲P) and the non-contact optical low coherence reflectometer (Lenstar LS ۹۰۰) devices for measuring Central Corneal Thickness (CCT) of healthy corneas. A total of ۸۲ healthy volunteers were evaluated. The first observer used both the TopconTRK-۲P and Lenstar ۹۰۰ devices while the second observer only used the TopconTRK-۲P for the measurements. The measurements with either device were repeated three times for each patient, consecutively. The central corneal thickness measurements with the Topcon TRK-۲P revealed mean ± Standard Deviation (SD) values of ۵۵۳.۱ ± ۳۶.۱ micrometer (µm) for the first observer and ۵۵۲.۳ ± ۳۵.۹µm for the second observer and the mean ± SD of CCT was ۵۳۷.۳ ± ۳۴.۸µm with the Lenstar ۹۰۰. The difference between the CCT measurements of the observers using the Topcon TRK-۲P (P = ۰.۱۴۲) was insignificant. However, significantly lower measurements were found with the Lenstar ۹۰۰ compared with the Topcon TRK-۲P (P Ë‚ ۰.۰۰۱). The central corneal thickness measurements obtained by the Topcon TRK-۲P were found to have high repeatability for both observers with a lower SD, less than ۱% Coefficient of Variation (CV) and higher than ۰.۹۹ Intra-Class Correlation Coefficient (ICC) (Observer ۱: ۳.۷۷ SD, ۰.۶۸ CV and ۰.۹۹۵ ICC; the second observer: ۳.۵۸ SD, ۰.۶۵ CV and ۰.۹۹۵ ICC). There was an excellent inter-observer reproducibility between the two observers for Topcon TRK-۲P with ۲.۷۱ SD, ۰.۴۹ CV, and ۰.۹۹۴ ICC. The Bland-Altman plot showed high agreement between the two devices. These results suggest that the TopconTRK-۲P is a reliable device for evaluating CCT in healthy corneas compared with Lenstar ۹۰۰.