Evaluating central corneal thickness measurements with noncontact optical low-coherence reflectometry and contact ultrasound pachymetry

PURPOSE: To compare the central corneal thickness (CCT) measurements obtained with noncontact optical low-coherence reflectometry (OLCR) and ultrasound (US) pachymetry. DESIGN: Prospective, comparative observational study. METHODS: Three sequential ultrasonic measurements and a set of five OLCR scans of 52 eyes of 26 healthy subjects were recorded. Noncontact measurement was repeated five minutes after anesthetic drop instillation. RESULTS: Mean CCT values for noncontact OLCR and US pachymetry were 544.03 mu m and 548.66 mu m, respectively, with mean SDs of 0.97 mu m and 4.63 mu m, respectively. Noncontact OLCR measured on average 4.64 mu m less than US pachymetry (95% confidence interval -7.56 to -1-72; P =.003). The OLCR measured 1.68 mu m less than US pachymetry in the thinner cornea group (<= 548.7 mu m, n = 24) and 7.48 mu m less in the thicker group (n = 25). This difference was statistically significant (P =.04). CONCLUSIONS: There was agreement between the two pachymetric measurements. Noncontact OLCR appeared to measure slightly smaller than US pachymetry.