Quantitative evaluation of iris convexity in primary angle closure

center dot PURPOSE: In eyes with primary angle closure (PAC), we quantitatively evaluated anterior bowing of the iris by means of ultrasound biomicroscopy (UBM). center dot DESIGN: Retrospective, observational, and consecutive case series. center dot METHODS: A total of 203 phakic eyes with PAC that had not undergone any surgical or laser treatment were included. Using UBM, we measured anterior chamber depth (ACD) and iris convexity (IC): the maximum distance from the posterior surface of the iris to the iris plane passing through the pupillary margin of the iris and iris root. center dot RESULTS: The average IC was 0.22 +/- 0.1 mm, although there was considerable individual variation. The IC value was correlated weakly, albeit significantly, with age (r = 0.22, P < .01), and strongly with ACD (r = -0.57, P < .0001). center dot CONCLUSIONS: In eyes with PAC, older age and a more shallow ACD appear to be important causes of increased forward bowing of the iris resulting from pupillary block.