Use of laser peripheral iridotomy reduces the already low risk of AAC in PACS

A subanalysis of the Zhongshan Angle-Closure Prevention (ZAP) trial assessed the risk of acute angle closure (AAC) in eyes treated with laser peripheral iridotomy (LPI) and fellow untreated eyes.

Study design

The ZAP trial enrolled 990 patients with bilateral primary angle closure suspect (PACS) through community screening programs. Patients were treated with LPI in one randomly selected eye while the other served as an untreated control. During 6 years of follow-up, patients had their pupils pharmacologically dilated 6 times with 5% phenylephrine and 0.5% tropicamide. The main outcome measures were the incidence and risk of post-mydriasis AAC in LPI-treated and untreated eyes.

Outcomes

During the study period, 1 patient developed bilateral AAC and 4 patients developed unilateral AAC. All the unilateral AAC attacks occurred in the untreated eyes: 2 after dilation (one at 54 months and one at 72 months of follow-up) and 2 spontaneously. The AAC incidence rates were 1.11/1000 eye-years in the untreated eyes and 0.22/1000 eye-years in the treated eyes.

Limitations

Given the uniformity of the population in this study, the results may not be generalizable to other racial and ethnic groups.

Clinical significance

These results indicated that the risk of AAC in patients with PACS is extremely low, even in a higher-risk scenario with frequent pharmacologic mydriasis, and is even lower with the use of prophylactic LPI. It is likely reasonable to consider LPI in those patients with PACS who require frequent pharmacologic mydriasis.

Financial Disclosures: Dr. Igor Bussel discloses no financial relationships.