Purpose: To determine the prevalence of appositional angle closure in eyes with a shallow peripheral anterior chamber but no peripheral anterior synechia (PAS) in Japanese patients. Design: Cross-sectional study. Participants: Eighty eyes of 80 consecutive patients with a shallow peripheral anterior chamber, determined using the method of van Herick, and no PAS. Methods: The anterior chamber angle was classified according to Shaffer's grading with noncompression gonioscopy superiorly, inferiorly, temporally, and nasally. The absence of PAS was confirmed by compression gonioscopy if necessary. The presence of appositional angle closure and the trabecular-iris angle (T-I angle) was determined with ultrasound biomicroscopy in each quadrant under light and dark conditions. Factors related to appositional angle closure were studied using logistic analysis, and the covariates included gender, age, refraction, gonioscopic grading, and the quadrant of the angle measured. Main Outcome Measures: Gonioscopic grading of the angle width, the T-I angle, and the prevalence of appositional closure. Results: The gonioscopic grading (P<0.001 in light and dark) and the T-I angle (P<0.001 in light and dark) varied significantly among the 4 quadrants. Narrower angle gradings were observed more frequently superiorly. The T-I angle was narrower superiorly (in light) and inferiorly (in dark) (P<0.001 and P = 0.040, respectively). The T-I angle was significantly narrower in dark than in light (P<0.001). The sites with the narrower gonioscopic gradings tended to have a smaller T-I angle (P<0.001 and P = 0.006 in light and dark, respectively). Conclusions: Appositional angle closure was found in at least 1 quadrant in 46 (57.5%) of 80 eyes in light and in 68 eyes (85%) in dark. Logistic analysis showed that gonioscopic grading and the quadrant were significantly related to the presence of appositional angle closure in light and dark (P<0.003 for both comparisons). Appositional angle closure was frequently observed in eyes with a shallow peripheral anterior chamber, especially under dark conditions in Japanese patients. The angle width, evaluated with conventional gonioscopic grading, and the quadrant of the angle were significantly related to the presence of appositional angle closure.
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