Short-term variation of central corneal thickness measurements in keratoconus using the Tono-Pachymeter NT530P (Tonopachy (TM))

Repeatability of values is a crucial reliability index in any instrument used to measure ocular parameters. The purpose of this study was to investigate short-term variability of central corneal thickness (CCT) measurements in keratoconic eyes. The Tono-Pachymeter NT530P (Tonopachy (TM)) was used to take fifty successive automatic measurements of CCT of the right eyes of ten keratoconic subjects (six females and four males), aged 19 to 41 years (mean = 30.4 +/- 6.8 years). The means, standard deviations and variances of the measurements showed little variation with good repeatability. The inter-subject or overall mean values and standard deviations of the measurements were 452.1 +/- 30.3 pm. The Kolmogorov-Smirnov (K-S), Lilliefors and Shapiro-Wilks (S-W) tests showed that generally the data was normally distributed, with a few exceptions. The results of this study suggest that over short periods of time, the Tonopachy (TM) provides repeatable measures of CCT in keratoconic corneas.