Comparison of a computer-assisted laser pachometer with two ultrasonic pachometers in normal corneas

A computer-assisted laser pachometer was compared with two ultrasonic pachometers for intra- and interobserver error. Two observers each performed two examinations at 11 predetermined locations on the corneas of six subjects. The laser pachometer was found to have intra- and interobserver errors comparable to both of the ultrasonic pachometers. By performing multiple examinations on three subjects, the laser pachometer was found to have an average standard deviation of +/- 0.012 mm. Unlike ultrasonic pachometers, the laser pachometer has the advantage of being a noncontact method of evaluating corneal thickness, and does not require topical anesthesia; the trauma and anesthesia might alter corneal thickness by inducing epithelial edema. The nasal cornea was found to be slightly thicker than the temporal cornea in most patients. Lid closure for three hours caused a consistent thickening (about 6.3%) of central and peripheral cornea.