[Detecting appositional angle closure by photopic and scotopic ultrasound biomicroscopy]

To evaluate the prevalence of appositional angle closure in eyes with a shallow peripheral anterior chamber (AC) and the anatomic narrow chamber angle by photopic and scotopic ultrasonic biomicroscopy (UBM).

Prospective case series study. 379 eyes of 194 consecutive patients with the shallow peripheral AC and the anatomic narrow chamber angle, which was determined by Van Herick technique and gonioscopy, were collected from the clinic and an epidemiological study. The presence of appositional angle closure and the angle-opening distance (AOD) was determined with photopic and scotopic ultrasound UBM in eight positions. The prevalence of appositional angle closure and AOD calculated by photopic and scotopic ultrasound biomicroscopy were compared. Paired chi2 test and Wilcoxon test (SPSS 12.0) were used to determine any significant differences at P < 0.05.

The prevalence of appositional angle closure was found at least one position in 264 eyes (69.7%) by scotopic UBM and in 99 (26.1%) eyes by photopic UBM. The prevalence of appositional angle closure was significantly higher by scotopic UBM than by photopic UBM (xhi2 = 159.148, P = 0.000 respectively), and was the highest in superior quadrant. The narrower AC was, the higher prevalence of appositional angle closure occurred. Furthermore, 98.3% of patients with peripheral AC < 1/4 corneal thickness (CT) were found to have an appositional angle closure by scotopic UBM. The AOD varied significantly among the four quadrants and was significantly narrower by scotopic UBM than by photopic UBM (Z = - 7.471, - 15.407, - 16.237, -16.782; P = 0.000). AOD in superior quadrant was narrowest with highest of the prevalence of appositional angle closure.

The prevalence of appositional angle closure varied with the depth of AC and can be effectively detected by photopic and scotopic UBM, more preferably by scotopic UBM at the clinic and the mass screening.