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

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™) 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. Theinter-subject or overall mean values and standard deviations of the measurements were 452.1 ± 30.3 μm. The Kolmogorov-Smirnov (K-S), Lilliefors and Shapiro-Wilks (S-W) tests showed that gener- ally the data was normally distributed, with a few exceptions. The results of this study suggest that over short periods of time, the Tonopachy™ provides repeatable measures of CCT in keratoconic corneas. (S Afr Optom 2012 71(3) 102-108)