Comparison of A-scan, Scheimpflug Camera, and Orbscan for Measurement of Anterior Chamber Depth

ABSTRACT

PURPOSE: To assess the reproducibility and reliability of the A-scan, Scheimpflug camera and Orbscan Topography system in measuring anterior chamber depth (ACD) METHODS: In this prospective study of 207 eyes of 150 patients, ACD estimation prior to cataract surgery was done by three METHODS: A-scan, Scheimpflug camera, and Orbscan (in that order). One observer performed all measurements three times for each test. ACD was defined as the length between the center of anteror surface of cornea and the center of anterior lens surface. RESULTS: The mean ACD by the three methods were 2.86+/-0.46 mm, 3.22+/-0.46 mm, and 3.13+/-0.44 mm, respectively: the differences were statistically significant (P<0.01). The correlation coefficient between Scheimpflug camera and Orbscan was 0.93. The coefficient of variation for the three methods were 3.20% in the A-scan, 1.34% in the Scheimpflug camera, and 0.84% with Orbscan. CONCLUSIONS: Applanation A-scan gives lower measurements for ACD compared with Scheimpflug and Orbscan. There was good agreement between results obtained with the latter 2 methods based on optical principles. Orbscan had the best reproducibility of results among the three methods.