August 2019

GLAUCOMA

Research Highlight
Malignant glaucoma risk following laser peripheral iridotomy


by Maxine Lipner EyeWorld Senior Contributing Writer


Malignant glaucoma can sometimes result even from a safe laser iridotomy.
Source: David Greenfield, MD

 

Primary angle closure glaucoma (PACG) accounts for 25% of world-wide glaucoma and affects approximately 20 million people. Prophylactic laser peripheral iridotomy (LPI) is recommended in eyes with anatomically narrow anterior chamber angles who are at increased risk for PACG. Laser iridotomy is a common procedure in the U.S., with 50,000 procedures performed annually. A small subset of patients may develop adverse effects such as visual dysphotopsia due to stray light reaching the retina or transient IOP elevation. David Greenfield, MD, treated a 58-year-old patient with PACG who developed a rare complication following an uneventful LPI—malignant glaucoma.1
“It is extremely uncommon to develop malignant glaucoma as a complication of laser iridotomy, and there have only been approximately a dozen cases previously reported,” Dr. Greenfield said. “Typically, this is seen as a postoperative complication of glaucoma filtration surgery in hyperopic eyes and presents with elevated IOP and shallowing of both the peripheral and axial anterior chamber.” Although poorly understood, the pathophysiology is thought to involve an alteration of the anatomic relationship among the lens, ciliary body, anterior hyaloid face, and vitreous leading to diversion of aqueous into the posterior segment.
While the treatment may require surgical intervention, medical therapy can suffice in approximately 50% of patients, he noted. This patient was treated conservatively for about 7 months with cycloplegia and aqueous suppression. Despite normal IOP, the patient developed progressive shallowing of the anterior chamber and myopic shift, and ultimately required pars plana vitrectomy with lensectomy and placement of a posterior chamber IOL. This restored normal anterior segment anatomy, and the patient ended up with 20/15 best corrected visual acuity and an IOP of 11 mm Hg.
“One should consider this entity in eyes that develop progressive anterior shallowing with progressive myopia, as our patient did,” he said. “IOP elevation may not always occur, particularly in eyes with early onset malignant glaucoma.” It is important to note that practitioners should avoid performing an iridotomy in the fellow eye due to the high risk of developing bilateral malignant glaucoma.
New evidence suggests that the benefit of performing prophylactic LPI in primary angle closure suspects may be limited. Until recently, there was little data regarding the natural history of untreated narrow angle. The Zhongshan Angle Closure Prevention trial2 was a prospective randomized clinical trial and found that among 889 people aged 50–70 with bilateral PAC suspected who received prophylactic LPI in one eye and observation in the fellow eye, the overall beneficial effect of prophylactic LPI was limited given the extremely rare development of AACG in both groups after 6 years of follow-up. “Although extended follow-up is warranted, the authors suggest that widespread laser peripheral iridotomy in eyes with narrow angles in patients who are primary angle closure suspects might not necessarily be warranted unless they are diabetic and require frequent pupillary dilation or they have glaucomatous optic neuropathy,” Dr. Greenfield said. “Another caveat is that this study was performed in Guangzhou, China and may not be applicable to other populations.”

About the doctor

David Greenfield, MD
Douglas R. Anderson
Distinguished Professor
of Ophthalmology
Bascom Palmer Eye Institute
Miami

References

1. Greenfield JA, et al. Malignant glaucoma after laser peripheral iridotomy. J Glaucoma. 2019;28:e44–e45.
2. He M, et al. Laser peripheral iridotomy for the prevention of angle closure: a single centre, randomised controlled trial.
Lancet. 2019;393:1609–1618.

Financial interests

Greenfield: None

Contact information

Greenfield
: d.greenfield@med.miami.edu

Malignant glaucoma risk following laser peripheral iridotomy Malignant glaucoma risk following laser peripheral iridotomy
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