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

Abstract

To determine the prevalence of plateau iris in a cohort of primary angle closure suspects (PACSs) using ultrasound biomicroscopy (UBM). Cross-sectional observational study. Subjects over the age of 50 years diagnosed as PACSs. Subjects were randomized to undergo laser peripheral iridotomy (LPI) in one eye. Ultrasound biomicroscopy was performed before and a week after LPI. 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. 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. 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.