LPI is effective in deepening the angle recess in all forms of angle closure caused by pupillary block. However, some patients have persistent angle closure despite a patent iridotomy, and this requires further evaluation. LPI can be useful in controlling IOP in PAC patients, although approximately 40%–60% of PAC patients treated with LPI require long-term medical or surgical treatment as well. Iridotomy is also useful in the acute management of APAC. However, it is less effective than phacoemulsification for long-term IOP control. In 1 study, approximately 50% of patients who underwent LPI for APAC had IOP elevation above 21 mm Hg at 18 months, compared with 3% in the phacoemulsification group. Most PACG eyes will require additional IOP treatment despite iridotomy. The rate of conversion from PAC to PACG is low after iridotomy, though the rate of conversion from APAC to PACG is high despite iridotomy.
The Zhongshan Angle Closure Prevention (ZAP) trial prospectively enrolled 889 primary angle-closure suspects. Each patient had 1 eye treated with LPI, while the other eye was observed. At 6 years, control eyes were more likely to develop angle-closure disease (36 eyes vs 19 eyes; P = .004), most commonly on the basis of the formation of PAS. However, there was a very low rate of conversion in both groups overall and no significant difference in acute angle-closure events or IOP elevation >24 mm Hg. (See also Chapter 9, Treatment Controversies sidebar.)
He M, Jiang Y, Huang S, et al. Laser peripheral iridotomy for the prevention of angle closure: a single-centre, randomised controlled trial. Lancet. 2019;393(10181):1609–1618.
Radhakrishnan S, Chen PP, Junk AK, Nouri-Mahdavi K, Chen TC. Laser peripheral iridotomy in primary angle closure: a report by the American Academy of Ophthalmology. Ophthalmology. 2018;125(7):1110–1120.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.