Non-pupillary block angle-closure mechanisms: a comprehensive analysis of their prevalence and treatment outcomes

Purpose: To assess the prevalence and treatment outcomes of angle-closure mechanisms other than pupillary block in a population of Brazilian patients. Methods: A retrospective chart review was conducted to evaluate patients who had undergone laser peripheral iridotomy (LPI) due to occludable angles at a single institution between July 2009 and April 2012. An occludable angle was defined as an eye in which the posterior trabecular meshwork was not visible for ≥180° on dark-room gonioscopy. Key exclusion criteria were any form of secondary glaucoma and the presence of >90° of peripheral anterior synechiae. Collected data were age, race, gender, angle-closure mechanism (based on indentation goniocopy and ultrasound biomicroscopy), intraocular pressure (IOP), number of antiglaucoma medications and subsequent management during follow-up. If both eyes were eligible, the right eye was arbitrarily selected for analysis. Results: A total of 196 eyes of 196 consecutive patients (mean age 58.3 ± 11.6 years) who underwent LPI were included. In most of the patients [86% (169 patients; 133 women and 36 men]), LPI sucessfully opened the angle. Mean IOP was reduced from 18.3 ± 6.4 mmHg to 15.4 ± 4.5 mmHg after LPI (p<0.01). Among the 27 patients with persistent occludable angles, the most common underlying mechanisms were plateau iris (56%) and lens-induced component (34%). Most of these patients (85%) were treated with argon laser peripheral iridoplasty (ALPI); approximately 90% showed non-occludable angles following the laser procedure (mean IOP reduction of 18.9%), with no significant differences between patients with plateau iris and lens-induced components (p=0.34; mean follow-up of 11.4 ± 3.6 months). Conclusion: Our findings suggest that, in this population of Brazilian patients, several eyes with angle closure were not completely treated with LPI. In the present large case series involving middle-age patients, plateau iris was the leading cause of persistent angle closure and was effectively treated with ALPI. A detailed eye examination with indentation gonioscopy should always be performed after LPI to rule out persistent angle closure due to non-pupillary block mechanisms.