Comparison of Contact and Non-contact Pachymeters in the Measurement of Central Corneal Thickness (CCT)

Abstract

The Central Corneal Thickness (CCT) examination assists in the diagnosis of ocular diseases such as glaucoma, keratoconus and Fuch’s dystrophy (FD). Several instruments used for the measurement of CCT include the ultrasound pachymeter, optical coherence tomography(OCT) machine, specular microscopy, A- Scan etc. The aim of this study was to evaluate the relationship and determine the repeatability of CCT measurements in an OCT machine and an ultrasound pachymeter. This was an observational study carried out in Sight Care Specialist Eye clinic, Benin City, Nigeria. CCT measurements were taken three times from each participant using both instruments and the average was noted. The data were analysed using Pearson Correlation and Analysis of Variance (ANOVA). Eighty participants (49 males and 31 females) with mean age of 43.1 ± 17.2years participated in the study. The mean CCT value for the ultrasound pachymetry for the right eye was 545.46±44.56mm and for the left eye was 546.45±49.35mm. The mean CCT value for the OCT machine in the right eye was 525.32±42.17mm and for the left eye was 524.95±46.43mm. There was also a strong positive significant relationship between OCT and Pachymeter (r = 0.92, p = 0.001) in both eyes. The OCT machine slightly underestimates the CCT values when compared to ultrasound pachymetry, however both CCT  values were highly correlated. Therefore, the OCT machine can serve as an alternative for the measurement of CCT values due to the greater disadvantages associated with the use of ultrasound pachymetry.