Magnetic resonance imaging and Orbscan assessment of the anterior chamber

PURPOSE: To evaluate the correlation between white-to-white (WTW) distance as assessed by Orbscan II (Bausch & Lomb) and high-resolution magnetic resonance imaging (MRI) sulcus-sulcus (S-S) measures and to analyze the correlation between age and anterior chamber parameters. SETTING: Istituto per la Ricerca e la Cura del Cancro, Candiolo, Torino, Italy. METHODS: Eighty-eight patients had MRI with a 1.5 Tesla imager (GE Medical Systems) using a 3-inch circular coil. T1 weighted fast spin-echo scans were performed on the axial plane. Orbscan II was also used to measure WTW distance, K, anterior chamber depth (ACD), and lens curvature. One eye was randomly selected for analysis. Measures were compared using Spearman correlation, paired Student t test, and analysis of variance (ANOVA; post hoc: Scheffé). Intersession variability was performed in 10 patients. Ten MRI images were randomly selected and measured by 2 operators in a masked fashion (intrasession variability). RESULTS: Intersession and intrasession correlation was good for MRI (r = 0.89 and r = 0.92, respectively), and intersession was good for Orbscan (r = 0.91). When comparing Orbscan II and MRI results, the ACD was well correlated and not significantly different, whereas the S-S and the WTW measures were not correlated and significantly different. Lens thickness and lens diameter were directly correlated with age; S-S, WTW, lens curvature, and ACD were inversely correlated with age. CONCLUSIONS: Current methods of measuring the WTW were poorly correlated with anatomical measures. The S-S diameter and other anterior chamber structures significantly change with age, which could give rise to potential problems with posterior chamber phakic intraocular lens sizing position.