Evaluation of the anterior chamber angle in Asian Indian eyes by ultrasound biomicroscopy and gonioscopy

PURPOSE: To compare the ultrasound biomicroscopic measurement of the anterior chamber angle in Asian Indian eyes, with the angle width estimated by gonioscopy. MATERIALS AND METHODS: Participants: Patients with open and closed angles attending a glaucoma clinic were recruited for the study. OBSERVATION PROCEDURES: Temporal quadrants of the angles of patients were categorized by gonioscopy as Grade 0 to Grade 4, using Shaffer's classification. These angles were quantified by ultrasound biomicroscopy (UBM) using the following biometric characteristics: Angle opening distance at 250 micro (AOD 250) and 500 micro (AOD 500) from the scleral spur and trabecular meshwork-ciliary process distance (TCPD). The angles were further segregated as "narrow angles" (Schaffer's Grade 2 or less) and "open angles" (Schaffer's Grade 3 and 4). MAIN OUTCOME MEASURES: The UBM measurements were computed in each case and analyzed in relation to the gonioscopic angle evaluation. RESULTS: One hundred and sixty three eyes of 163 patients were analyzed. One hundred and six eyes had "narrow angles" and 57 eyes had "open angles" on gonioscopy. There was a significant difference among the mean UBM measurements of each angle grade estimated by gonioscopy (P < 0.001). The Pearson correlation coefficient between all UBM parameters and gonioscopy grades was significant at the 0.01 level. The mean AOD 250, AOD 500 and TCPD in narrow angles were 58+/-49 micro, 102+/-84 micro and 653+/-124 respectively, while it was 176+/-47 micro, 291+/-62 micro and 883+/-94 micro in eyes with open angles (P < 0.001) respectively. CONCLUSIONS: The angle width estimated by gonioscopy correlated significantly with the angle dimensions measured by UBM. Gonioscopy, though a subjective test, is a reliable method for estimation of the angle width.