Comparison of three methods of measuring corneal thickness and anterior chamber depth

PURPOSE: To compare three different methods of measuring corneal thickness (CT) and anterior chamber depth (ACD). DESIGN: Prospective clinical trial (Medical University of Vienna, Austria). METHODS: Central CT (CCT), CT at four peripheral points, and central ACD were measured in 88 eyes of 44 healthy subjects with the Pentacam (rotating Scheimpflug camera; Oculus, Wetzlar, Germany), Orbscan I (scanning-slit topography system; Orbtek Inc, Salt Lake City, Utah, USA), and AC-Master (partial coherence interferome try; Zeiss Meditec, Jena, Germany), and the results were compared. RESULTS: The upper (lower) limits of agreement for CT measurements were 7.9 (-22.2) mu m between AC- Master and Pentacam, 17.6 (-32.5) mu m between AC- Master and Orbscan, and 25.2 (-25.9) mu m between Pentacam and Orbscan. Correlation was high between all three methods (r = 0.94 to 0.97). The upper and lower limits of agreement for ACD were 0.174 (-0.251) mm between AC-Master and Pentacam, 0.406 (-0.004) mm between AC-Master and Orbscan, and 0.384 (0.095) mm between Pentacam and Orbscan. Correlation was high between the three methods (r = 0.96 between Orbscan and Pentacam; others 0.92). Correlation was lower for the CT measurements at the four peripheral points. CONCLUSIONS: The CCT and ACD values obtained by Pentacam, Orbscan, and AC-Master measurements correlated well and showed few outliers. The two new systems (Pentacam, AC,Master) provide a reliable, easy-to-use, noncontact method of measuring CCT and ACD. Larger differences occurred only when measuring peripheral CT values, especially between AC,Master and the other two methods.