Plateau Iris in Primary Angle Closure Glaucoma: An Ultrasound Biomicroscopy Study.

PURPOSE: To determine prevalence and anterior segment morphology of plateau iris in patients with primary angle closure glaucoma (PACG) after laser peripheral iridotomy using ultrasound biomicroscopy (UBM).

METHODS: In this prospective study, 262 PACG patients and 144 normal controls underwent UBM examination. Plateau iris in a quadrant was defined by the presence of anteriorly directed ciliary process, absent ciliary sulcus, steep iris root from its point of insertion followed by a downward angulation, flat iris plane, and irido-angle contact in the same quadrant. At least 2 quadrants had to fulfill these UBM criteria.

RESULTS: UBM analysis showed plateau iris in 83/262 (31.68%, 95% confidence interval: 26.7%-37.9%) PACG eyes, it was common in female individuals (61.44%), and patients were significantly younger than PACG patients (P=0.006). Plateau iris was found in superior quadrant in 19/83 (22.89%) eyes, inferior quadrant in 19/83 (22.89%) eyes, nasal quadrant in 21/83 (25.3%) eyes, and temporal quadrant in 24/83 (28.91%) eyes. In plateau iris patients, the central anterior chamber depth was shallower, the anterior chamber angle, the scleral-iris angle, and the sclera-ciliary process angle were significantly narrower, and the trabecular ciliary process distance and the iris ciliary process distance were significantly shorter in patients than in PACG subjects.

CONCLUSIONS: Patients with plateau iris had significantly shallow central ACD when compared with those with pupillary block and normal eyes. After laser peripheral iridotomy, about a third of PACG eyes had plateau iris. This is clinically important because these patients can develop synechial angle closure and should be followed up closely.