Comparison of Central Corneal Thickness Measurement by Specular Microscopy, Optical Coherence Tomography, Optical Biometry and Ultrasound Pachymetry in Normal Eyes

Abstract

BACKGROUND
 Precise central corneal thickness (CCT) measurement is of utmost importance in various corneal diseases and refractive procedures. Various methods are available to measure CCT. But studies comparing CCT measurements with different devices have shown variable results. This study compares the CCT measurements by different devices and Ultrasound Pachymetry (USP).
 METHODS
 This prospective study that was conducted from October 2017 to June 2019 included 100 subjects aged more than 18 years and CCT was measured by non-contact specular microscopy (NCSM), spectral domain optical coherence tomography (SD-OCT), optical biometry (OB) and USP in normal eyes. For every patient and with each device, three readings were taken and an average was recorded. The data recorded per protocol was analyzed using Intraclass correlation coefficient and Bland-Altman analysis.
 RESULTS
 The mean value of CCT with NCSM, SD-OCT, OB, USP was 528.98±32.18µm, 532.64±30.49µm, 517.47±31.89µm and 533.39±33.44µm, respectively. The intraclass correlation was found to be maximum between NCSM and USP (0.953, p<0.001). The mean paired difference of CCT values with SD-OCT and USP was statistically insignificant (-0.75±14.73, p=1.00) whereas the difference obtained with all other devices was statistically significant.
 CONCLUSIONS
 A statistically significant positive correlation (p<0.001) was observed on comparing all the four devices with each other for measurement of CCT. The OCT had the best agreement and also positively correlated with USP. Hence, we conclude that OCT can be an effective alternative to USP for measuring CCT.