Acute Angle-Closure Attacks Are Uncommon in Primary Angle-Closure Suspects after Pharmacologic Mydriasis

Angle-closure glaucoma is a major cause of blindness worldwide that carries an excessive risk of severe, bilateral visual impairment. A common concern among clinicians is the precipitation of acute angle-closure (AAC) attacks because of mydriasis. We evaluated the risk of AAC after pharmacologic dilation in Chinese individuals classified as having bilateral primary angle-closure suspects (PACSs).Randomized, interventional, controlled trial.A total of 889 patients with bilateral PACSs, aged between 50 and 70 years, were identified through community screening in Guangzhou, China, and enrolled in the study.In the Zhongshan Angle-Closure Prevention Trial, bilateral PACSs were treated with laser peripheral iridotomy (LPI) in 1 randomly selected eye, with the fellow eye serving as an untreated control. Over 72 months of follow-up, the participants had their pupils pharmacologically dilated 6 times with 5% phenylephrine and 0.5% tropicamide.Incidence and risk of post-mydriasis AAC in LPI-treated and untreated, control eyes classified as PACSs.One bilateral AAC attack occurred after mydriasis at the 2-week post-LPI visit. No other AAC events occurred in the LPI-treated eyes. In the untreated eyes, 4 additional attacks occurred: 2 occurred after dilation (1 at 54 months and 1 at 72 months of follow-up) and 2 occurred spontaneously. The risk of post-mydriasis AAC in the untreated eyes was 1 attack in 1587 dilations. The risk of spontaneous AAC in the untreated eyes was 0.44 per 1000 eye-years (95% confidence interval, 0.11-1.77 per 1000 eye-years).The risk of incident AAC attacks in PACSs was extremely low, even in a higher-risk group that underwent repeated pharmacologic pupillary dilation over 6 years of follow-up. Prophylactic LPI reduced this small but real risk. This trial was registered at ISRCTN.com as ISRCTN45213099.