Comparison of the Prevalence of Plateau Iris Configurations Between Angle-closure Glaucoma and Open-angle Glaucoma Using Ultrasound Biomicroscopy

Purpose: To determine the prevalence of plateau iris configurations in acute primary angle-closure (APAC), chronic angle-closure glaucoma (CACG), and open-angle glaucoma (OAG) eyes using ultrasound biomicroscopy. Materials and Methods: The study included fellow eyes of 27 APAC patients, 26 OAG patients, and 26 CACG patients with no history of APAC. Patients with a history of earlier intraocular surgery or argon laser peripheral iridoplasty were excluded from the study. Eyes that had not undergone laser peripheral iridotomy were excluded from APAC and CACG groups. Radial scans were carried out using ultrasound biomicroscopy in all 4 quadrants. A plateau iris configuration within a quadrant was defined by the presence of an anteriorly positioned ciliary process, a narrow ciliary sulcus, a steeply rising peripheral iris, followed by a downward angulation from the corneoscleral wall and the presence of a flat iris plane. Eyes with plateau iris configurations were defined as those having at least 2 quadrants fulfilling these criteria. Results: Plateau iris configurations were found in fellow eyes of 10 of 27 patients with (37.0%) APAC, 9 of 26 (34.6%) patients with CACG, and 5 of 26 (19.2%) patients with OAG. No significant difference in the prevalence of plateau iris configurations was observed among the 3 groups (P = 0.314, chi(2) test). Conclusions: Eyes with OAG had a higher rate of plateau iris configurations than expected. Longitudinal studies to evaluate plateau iris height are required to determine its significance in the pathogenesis of angle-closure glaucoma.