Comparison of optical coherence tomography and ultrasound biomicroscopy for detection of narrow anterior chamber angles

Objective: To assess the accuracy of classification of narrow anterior chamber (AC) angles using quantitative imaging by optical coherence tomography (OCT) and ultrasound biomicroscopy (UBM). Design: Observational comparative study. Methods: A high-speed (4000 axial scans/s) anterior segment OCT prototype was developed using a 1.3-mu m light source. Seventeen normal subjects (17 eyes) and 7 subjects (14 eyes) with narrow angle glaucoma were enrolled. All subjects underwent gonioscopy, OCT, and UBM. Quantitative AC angle parameters (angle opening distance, angle recess area, and the trabecular-iris space area [a new parameter we have defined]) were measured from OCT and UBM images using proprietary processing software. Main Outcome Measures: Specificity and sensitivity in identifying narrow angles with image-derived AC angle parameters. Results: Eight of 31 eyes were classified as having narrow angles (Shaffer grade <= 1 in all quadrants). The AC angle parameters measured by both OCT and UBM had similar mean values, reproducibility, and sensitivity-specificity profiles. Both OCT and UBM showed excellent performance in identifying eyes with narrow angles. Areas under the receiver operating characteristic curves for these parameters were all in the range of 0.96 to 0.98. Conclusions: Optical coherence tomography was similar to UBM in quantitative AC angle measurement and detection of narrow angles. In addition, it was easier to use and did not require contact with the eye. Optical coherence tomography is a promising method for screening individuals at risk for narrow angle glaucoma.