Prediction of angle closure after laser peripheral iridotomy: The fourteen-year Zhongshan Angle Closure Prevention trial

Anterior chamber angles in primary angle closure suspects (PACS) can continue to narrow after laser peripheral iridotomy (LPI). The aim of this study is to identify risk factors and develop prediction models for the progression in LPI-treated eyes during a 14-year follow-up. From 2008 to 2010, 889 Chinese participants aged 50-70 years with bilateral PACS were enrolled in the Zhongshan Angle Closure Prevention (ZAP) trial and received LPI in one randomly selected eye. Examinations before LPI included Goldmann tonometry, ultrasound A-scan biometry, both light-room and dark-room anterior-segment optical coherence tomography (AS-OCT). Logistic regression models were built to predict the 14-year risk of progression in PACS eyes after LPI (peripheral anterior synechiae, intraocular pressure [IOP] ��24mmHg, or acute angle closure). Within 370 eligible PACS eyes, 26 progressed to PAC during 14 years after LPI. For both light-room and dark-room AS-OCT metrics before LPI, the narrowing of anterior chamber angle was identified as risk factor for the 14-year risk of progression in LPI-treated PACS eyes. In addition, change in IOP after dark-room prone provocative test and change in lens vault from light to dark before LPI were found to be negatively associated with the risk of progression during 14 years after LPI. Based on aforementioned predictors, multivariable logistic models provided good performance in the prediction for long-term risk of progression after LPI (area under the curve = 0.80-0.84). This study suggested that closer monitoring is still required for PACS eyes at high risk of progression even after prophylactic LPI.