In this study utilizing the results of the Zhongshan Angle-Closure Prevention (ZAP) Trial, the rates of acute angle-closure (AAC) attacks upon dilation were evaluated. Among participants who were classified as primary angle-closure suspects (PACS), one eye was randomized to laser peripheral iridotomy (LPI) at the start of the study. There were 889 subjects enrolled in the ZAP Trial and dilation occurred at two weeks, six months, 18 months, 36 months, 54 months, and 72 months. There was a total of five patients who developed an AAC attack during the course of the study. One case was a bilateral case (both a control eye and a LPI-treated eye) and four were unilateral cases (all control eyes). Among the five patients (six eyes) with AAC, the ones that occurred after dilation were one LPI-treated eye and two control eyes. From these results, the risk of developing an attack after dilation was estimated to be 1 in 1587 among non-LPI eyes and 1 in 4762 among LPI-treated eyes.
The authors conclude that it is extremely rare to develop an AAC attack after dilation in LPI-treated eyes, and that it is reasonably safe to do so when needed
The authors conclude that it is extremely rare to develop an AAC attack after dilation in LPI-treated eyes, and that it is reasonably safe to do so when needed. Among PACS eyes which have not received LPI, the risk with multiple dilations is small but should be considered. Patients who require routine dilation, such as those with diabetic retinopathy, may wish to consider LPI due to the additive risk with multiple dilations.
Patients who require routine dilation, such as those with diabetic retinopathy, may wish to consider LPI due to the additive risk with multiple dilations
Overall, the results of the present study are very helpful to clinicians as this scenario of whether to dilate in PACS eyes occurs commonly. The large population cohort and prospective nature of this study give credibility to the findings and recommendations. However, it should be noted that there are limitations due to the study design including the inclusion of only Chinese subjects, community recruitment causing potential selection bias, exclusion of very high-risk patients (eyes positive on the dark room prone provocative test), and the aggressive use of medications to prevent IOP elevation after LPI. Many of these issues may lead to underestimation of the true risk for AAC after dilation.