Comparison of central corneal thickness measurements between optical and ultrasound pachometers

Abstract

The central corneal thickness measured by 2 methods was compared in 31 normal subjects. At each of the two examinations, central corneal thickness was evaluated by an ultrasonic and an optical method. Reliability was assessed by an analysis of variance (ANOVA) between repeated measurements for the electronic digital and the Humphrey ultrasonic pachometers. The former revealed a systematic right-left difference, the left cornea being significantly thicker. This phenomenon has been observed in many studies and has been attributed to a measurement not done perpendicularly to the cornea. Angle lambda measured on eight subjects was nasal in all cases. A very high correlation coefficient was obtained between the two methods of central pachometry and the results obtained for the right eye by these two methods were not significantly different. Also, a small but significant negative correlation was observed between the central corneal curvature and the corneal thickness as evaluated by either pachometer.