**11. SPAC examination**

All subjects underwent examination with SPAC. Paramedical staff correctively measured the ACD of 658 subjects (703 eyes of 354 men, 607 eyes of 304 women). SPAC examines the region from the optical axis to the temporal limbus in approximately 0.66 s, taking 21 consecutive slitlamp images at 0.4-mm intervals. The camera-captured cross-sectional slit-lamp images are immediately subjected to analysis, and the radius of curvature, the corneal thickness, and ACD values are displayed. The SPAC yields numeric and categorical grades that are calculated by comparison with the ACD values derived from a sample of Japanese subjects [18]. In our study, the range of ACD values of the patients was divided into 12 groups, each representing an equal increment in the ACD. Group 12 consisted of eyes with the deepest mean ACD values, whereas eyes with the shallowest mean ACD values were allocated to group 1.

Based on the data provided by SPAC, the following parameters were determined: distri‐ bution of ACD from the central and the peripheral region, distribution of the grades of ACD, and frequency of suspected (S) or possible (P) angle-closure eyes. The high risk of angle closure group includes eyes judged as S or P, or grade ≤5 by SPAC. These eyes were eligible for the definitive examination, The SPAC automatically calculates central ACD along the visual axis. Peripheral ACD means anterior chamber depth at 5.6 mm apart from the anterior pole of the lens (Fig. 3).

Of 1420 eyes of the 710 participants of the glaucoma screening study, reliable SPAC re‐ sults were analyzed in 1310 eyes of 658 participants (Table 3). 104 eyes of fifty two par‐ ticipants were omitted from the study. The main reason for exclusion were that SPAC measurements could not be completed at the screening sites for various reasons, such as subjects' ocular or physical problems. 100 eyes were unable to fixate the fixation lamp due to poor visual acuity, and 2 subjects (4 eyes) were unable to keep their faces on the chin rest during measurement. Between the included and excluded subjects, the male/ female ratio was not statistically different (P = 0.44, χ2 test).

Screening for Narrow Angles in the Japanese Population Using Scanning Peripheral Anterior Chamber Depth Analyzer http://dx.doi.org/10.5772/54556 261


**Table 3.** Number of patients and eyes and the percentage of eyes (in parenthesis) examined by SPAC in each age group.
