Ultrasound biomicroscopic and conventional ultrasonographic study of ocular dimensions in primary angle-closure glaucoma

Abstract

Objective To determine the biometric findings of ocular structures in primary angle-closure glaucoma (PACG). Design An observational case series with comparisons among three groups (patients with acute/intermittent PACG [A/I-PACG], patients with chronic PACG [C-PACG], and normal subjects [N]). Participants A total of 54 white patients with PACG (13 male, 41 female) were studied: 10 with acute, 22 with intermittent, and 22 with chronic types of PACG. Forty-two normal white subjects (11 male, 31 female) were studied as control subjects. Only one eye was considered in each patient or subject. Testing Ultrasound biomicroscopy (UBM) and standardized A-scan ultrasonography (immersion technique) were performed in each patient during the same session or within 1 to 3 days. Main outcome measures The following A-scan parameters were measured: anterior chamber depth (ACD), lens thickness (LT), axial length (AL), lens/axial length factor (LAF), and relative lens position (RLP). Ten UBM parameters were measured, the most important of which were anterior chamber angle, trabecular-ciliary process distance (TCPD), angle opening distance at 500 μm from the scleral spur (AOD 500), and scleral-ciliary process angle (SCPA). Results Compared to normal subjects, the patients with PACG presented a shorter AL (A/I-PACG = 22.31 ± 0.83 mm, C-PACG = 22.27 ± 0.94 mm, N = 23.38 ± 1.23 mm), a shallower ACD (A/I-PACG = 2.41 ± 0.25 mm, C-PACG = 2.77 ± 0.31 mm, N = 3.33 ± 0.31 mm), a thicker lens (A/I-PACG = 5.10 ± 0.33 mm, C-PACG = 4.92 ± 0.27 mm, N = 4.60 ± 0.53 mm), and a more anteriorly located lens (RLP values, A/I-PACG = 2.22 ± 0.12, C-PACG = 2.34 ± 0.16, N = 2.41 ± 0.15). The LAF values in A/I-PACG, C-PACG, and N were 2.28 ± 012, 2.20 ± 0.11, and 1.97 ± 0.12, respectively. Anterior chamber angle (A/I-PACG = 11.72 ± 8.84, C-PACG = 19.87 ± 9.83, N = 31.29 ± 9.18°) and SCPA (A/I-PACG = 28.71 ± 4.02, C-PACG = 30.87 ± 6.04, N = 53.13 ± 9.58°) were narrower, TCPD (A/I-PACG = 0.61 ± 0.12 mm, C-PACG = 0.71 ± 0.14 mm, N = 1.08 ± 0.22 mm) and AOD 500 shorter (A/I-PACG = 0.13 ± 0.09 mm, C-PACG = 0.21 ± 0.10 mm, N = 0.36 ± 0.11 mm) in patients with PACG. All the biometric differences proved statistically significant using the one-way analysis-of-variance test. Conclusions In patients with PACG, the anterior segment is more crowded because of the presence of a thicker, more anteriorly located lens. The UBM confirms this crowding of the anterior segment, showing the forward rotation of the ciliary processes. A gradual progressive shift in anatomic characteristics is discernible on passing from normal to chronic PACG and then to acute/intermittent PACG eyes.