Prevalence of Plateau Iris in Primary Angle Closure Suspects. An Ultrasound Biomicroscopy Study

Purpose: To determine the prevalence of plateau iris in a cohort of primary angle closure suspects (PACSs) using ultrasound biomicroscopy (UBM). Design: Cross-sectional observational study. Participants: Subjects over the age of 50 years diagnosed as PACSs. Intervention: Subjects were randomized to undergo laser peripheral iridotomy (LPI) in one eye. Ultrasound biomicroscopy was performed before and a week after LPI. Main Outcome Measures: Ultrasound biomicroscopy images were qualitatively assessed using standardized criteria. Plateau iris was defined in a quadrant by the presence of an anteriorly directed ciliary body, an absent ciliary sulcus, a steep iris root from its point of insertion followed by a downward angulation from the corneoscleral wall, presence of a central flat iris plane, and irido-angle contact. At least 2 quadrants had to fulfil the above criteria for an eye to be defined as plateau iris. Results: Two hundred five subjects were enrolled; UBM images of 167 subjects were available for analysis. Plateau iris was found in 54 of 167 (32.3%) PACS eyes after LPI. Quadrantwise analysis showed that 44 of 167 (26.3%) eyes had plateau iris in 1 quadrant, 36 (21.5%) in 2 quadrants, 16 (9.5%) in 3 quadrants, and 2 (1.2%) in all 4 quadrants. Plateau iris was most commonly observed in the superior and inferior quadrants. Conclusions: Using standardized UBM criteria, plateau iris was found in about a third of PACS eyes after LPI. Prospective longitudinal studies are required to determine the clinical significance of this finding for the management of PACSs.