Comparison of central corneal thickness measurements using different imaging devices and ultrasound pachymetry

PURPOSE: To compare central corneal thickness (CCT) measurements obtained by the AL-Scan, Lenstar LS900, Galilei, and ultrasound pachymetry (UP) in normal and cataractous eyes. METHODS: Eighty eyes of healthy subjects were included in the study. Each subject was assessed by four different methods of measurements using the AL-Scan, Lenstar LS900, Galilei, and UP by a single examiner. To assess the intraobserver repeatability, three consecutive measurements were taken for the AL-Scan. RESULTS: The mean CCT [± standard deviation (SD)] for the AL-Scan, Lenstar LS900, Galilei, and UP were 554.6 ± 30.9 μm, 542.9 ± 31.3 μm, 570.7 ± 30 μm, and 552.7 ± 32.8 μm, respectively. The differences between pairs of mean CCT for the methods are statistically significant for the pairs of Galilei–UP, AL-Scan–Galilei, and Lenstar LS900–Galilei. Bland–Altman plots showed that AL-Scan–UP have the closest agreement, followed by Lenstar–UP and AL-Scan–Lenstar. Galilei was found to have the poorest agreement with the other three methods. The intraobserver repeatability of the AL-Scan was very good with an intraclass correlation coefficient (ICC) of 0.980. CONCLUSION: We found that CCT measurements between the AL-Scan–UP, Lenstar LS900–UP, and AL-Scan–Lenstar LS900 showed very strong correlation and comparable agreement. AL-Scan–UP showed the closest agreement and these devices can be used interchangeably in clinical practice. Galilei significantly showed higher value of CCT compared to other methods. It was also observed that the Al-Scan had excellent intraobserver repeatability.