Background: Primary angle closure glaucoma (PACG) accounts for nearly 50% of global glaucoma blindness. There are currently no public health strategies to deal with this problem. Screening and prophylactic treatment of primary angle closure suspects (PACS) with laser peripheral iridotomy (LPI) may form a feasible population-level intervention. However, more information about the natural history of PACS is required before such an approach could be considered. Methods: Six hundred and forty-four participants aged 50 years with a central anterior chamber depth (cACD) of Results: At follow-up, 41 participants (20.4%, 95% CI: 14.8 to 25.7) were diagnosed as having incident PACS. Narrower angles, identified by grading of limbal chamber depth and gonioscopy at baseline, were strongly associated with incident occludable angles (p = 0.01 and pConclusions: Narrower angles as determined by limbal chamber depth grading and gonioscopy at baseline were the main risk factors identified for the development of occludable angles.