Intraobserver and interobserver reproducibility in the evaluation of ultrasonic pachymetry measurements of central corneal thickness

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Abstract
Purpose: To assess reproducibility of central corneal thickness (CCT) measurement by means of ultrasonic pachymetry. Methods: Fifty one volunteers underwent three sessions of CCT measurements, each consisting of three CCT measurements, performed by each of three different observers. Intra- and interobserver reproducibility was calculated by means of intraclass correlation coefficient (ICC). The expected range of variability between two independent evaluations was calculated using scatter plots of each test-retest difference against their mean. The standard deviation of the mean differences in the test-retest scores was used to describe the differences in the score spread. Results: The ICC ranges of the intra- and interobserver evaluations were 0.95–0.97 and 0.89–0.95 respectively; the expected variability was ⩽±1% and ⩽± 2% respectively (95% confidence interval). Conclusions: The measurement of CCT by means of ultrasonic pachymetry is highly reproducible.