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  • Glaucoma

    This study identified anterior segment OCT (AS-OCT) biometric parameters that are risk factors for progression from primary angle-closure suspect (PACS) to more severe disease and that can help in risk stratification.

    Study design

    This was a prospective, observational study conducted as part of the Zhongshan Angle Closure Prevention (ZAP) trial. A total of 643 Chinese patients (643 eyes) with untreated PACS underwent complete baseline eye examinations, including gonioscopy and AS-OCT imaging, as part of the ZAP trial. Participants were re-examined at 2 weeks and 6, 18, 36, 54, and 72 months after the initial baseline exam. The primary focus of the study was to identify the biometric risk factors which predict progression from PACS to primary angle closure (PAC) or acute angle closure (AAC).


    Thirty-four of the 643 eyes (5.3%) progressed from PACS to PAC or AAC, consistent with the overall rate of progression (5.4%) among participants who completed the ZAP trial. Most cases of progression were caused by peripheral anterior synechiae (PAS). In multivariate models, the AS-OCT biometric parameters of narrower horizontal angle opening distance from the scleral spur and flatter horizontal iris curvature were significantly associated with progression to PAC or AAC. Older age, higher IOP, and greater lens thickness at baseline were also factors which increased risk for progression, but cumulative gonioscopy scores were not.


    All participants in the ZAP trial were Chinese and between age 50 and 70 years, which may limit the generalizability of these results in other populations. Additionally, the number of patients who progressed in the study was small. Another possible limitation is that the study worked with a definition of PAC (IOP >24 mm Hg or any PAS) that was narrower than its original epidemiologic definition (IOP >21 mm Hg or any PAS).

    Clinical significance

    This study demonstrates that AS-OCT imaging of the anterior segment may be a better tool than gonioscopy for determining risk of progression from PACS to PAC or AAC. These biometric parameter measurements can help to identify patients with early angle closure who are at higher risk of progression to more severe disease.