Reproducibility and variation of corneal thickness in different locations in the cornea as measured by an ultrasonic pachymeter.

Corneal thickness was measured in nine positions of nineteen normal eyes with an ultrasonic pachymeter. A standardized protocol was used to examine for intraobserver and interobserver variation, day to day variation, and time of day variation in the measurement of corneal thickness. No statistically significant difference was noted for most points in intraobserver, interobserver, day to day, or different time of day variation measurements. However, it was noted that central measurements of corneal thickness tended to be less variable (more reproducible) than paracentral (p = .0366) and peripheral (.0032) measurements. Paracentral measurements were less variable than peripheral measurements (p = .0323). While this was a small study, 95% confidence intervals were also calculated for each of the nine corneal positions where measurements were performed.