Is peripheral iridotomy valid?

Dermot McGrath

Posted: Monday, February 1, 2021

Beatrice Des Marchais MD, PhD

Despite a re-evaluation of its utility in recent years, laser peripheral iridotomy (LPI) remains standard first-line treatment in patients with narrow angles, narrow angle glaucoma and acute closed angle glaucoma and eyes at risk for this condition, according to Beatrice Des Marchais MD, PhD.
“Glaucoma management continues to change and evolve in our daily practices and the indications for LPI have been revised accordingly in recent years. However, some fundamentals have not changed, and I still offer LPI to selected patients, informing them of the risk of complications and photopsia in particular,” she said at the World Ophthalmology Congress 2020 Virtual.Dr Des Marchais said that LPI has been used since the 1980s both as treatment and prevention of angle closure glaucoma.
“This has been the case even though the natural history of untreated shallow angle is not known and the efficiency of LPI is not obvious based on the evidence in the scientific literature,” she said.
One of the few controlled studies to look at the efficacy of prophylactic LPI in bilateral angle-closure suspects, the Zhongshan Angle Closure Prevention (ZAP) trial, suggested that perhaps laser iridotomy is not required in all angle-closure suspects, she said.
The study included 889 patients at different centres in China who were randomised to receive laser iridotomy in one eye, while the other eye remained an untreated control. The risk of converting from suspect angle closure to confirmed angle closure was low during this six-year study.
“The ZAP trial came out against the widespread practice of LPI in suspect cases because of the limited cost-benefit ratio. Laser iridotomy decreases the risk of this conversion, although the incidence of primary angle closure is remarkably low,” she said.
Based on a literature review carried out in conjunction with Jean-Philippe Rozon, Dr Des Marchais said it was important to check IOP after LPI for all patients with more than one risk factor.
“We need to watch for bleeding in the anterior chamber, pigment dispersion, high IOP pre-treatment, Asian ethnicity, patients with thick iris or those with pre-existing optic nerve damage,” she said.
Dr De Marchais also carried out a separate study to determine the rate of gonioscopy after LPI treatment.
“We were surprised that despite recommendations only 28% of patients received gonioscopy exams as part of their standard follow-up,” she said.
To address the situation, an interventional plan was implemented to educate surgeons and staff on the necessity to perform gonioscopy as part of the follow-up to LPI.
“It was successful, and our results one year later showed an increased rate of gonioscopy post iridotomy from the documented 28% to 64%, proving the value of an interventional plan to improve patient safety and quality of care,” she concluded.