Comparison of central corneal thickness measurements by ultrasound pachymetry, konan noncontact optical pachymetry, and orbscan pachymetry

PURPOSE: To assess the repeatability of two optical techniques for measurement of central corneal thickness and to compare the validity of these techniques with standard ultrasound pachymetry. METHODS: Corneal thickness was measured twice with Konan optical pachymetry, Orbscan optical pachymetry, and 3 times by conventional ultrasound pachymetry in 100 eyes of 50 healthy volunteers between the ages of 22 and 74 years. The repeatability of measurements of each instrument was determined and compared. Validity was determined by comparing the means of the first Konan and Orbscan measurements to the mean of standard ultrasound pachymetry. Intraclass correlation coefficients (ICCs) were calculated, and their confidence intervals (CIs) were determined. RESULTS: Repeatability of ultrasound pachymetry had an ICC of 0.905 (95% CI: 0.870-0.932). The Konan pachymeter had an ICC of 0.947 (95% CI: 0.922-0.964), and the Orbscan pachymetry yielded an ICC of 0.972 (95% CI: 0.959-0.981). Validity of Konan pachymetry had an ICC of 0.730 (95% CI: 0.623-0.810). Orbscan pachymetry had an ICC of 0.865 (95% CI: 0.805-0.907). CONCLUSIONS: Both of the newer optical methods for determining corneal thickness produced measurements of greater repeatability than the standard ultrasound technique. Orbscan pachymetry provides greater repeatability (P = 0.02) and validity (P = 0.007) than the Konan optical pachymeter. © 2008 by Lippincott Williams & Wilkins.