FEATURE 24 EWAP DECEMBER 2023 W hen it comes to malignant glaucoma, why it occurs, its management, and if possible, its prevention, Matt Schlenker, MD, and Devesh Varma, MD, both think it’s important to first discuss some of the misunderstanding that has surrounded this topic. The term “malignant glaucoma” was coined by Albert von Graefe in 1869 when he published a paper on acute angle closure glaucoma in patients after peripheral iridotomy, with shallowing of the anterior chamber and high intraocular pressure. 1 Dr. Varma and Dr. Schlenker said there is a history of malignant glaucoma being described as aqueous misdirection. As Dr. Varma put it, “In the early days, malignant glaucoma was described as the shallowing of the peripheral and central anterior chamber with high pressure. People weren’t sure what the cause was. They thought maybe aqueous was going in the wrong direction and called it aqueous misdirection.” Dr. Varma and Dr. Schlenker said this is not what’s happening. The seminal paper in 2009 by Harry Quigley, MD, cleared up what’s happening in these cases and began to change what Dr. Varma said is a misnomer. 2 In the abstract of the paper, Dr. Quigley wrote: When the pupil dilates, the iris typically decreases its volume by losing extracellular fluid. Eyes with angle-closure lose less iris volume with pupil dilation, contributing to obstruction of the trabecular meshwork. Expansion of choroidal volume is a dynamic phenomenon and is a major risk factor in angle-closure. The mechanism of malignant glaucoma seems likely to result from poor conductivity of fluid through the vitreous, and past suggestions that it results from “misdirected” aqueous are not consistent with physiological principles. When malignant glaucoma can occur There are a few clinical scenarios in which malignant glaucoma is more likely to occur. Dr. Schlenker said the most profound precipitating event is shallowing of the anterior chamber, for instance after filtering surgery, such as a trabeculectomy or tube shunt surgery in at-risk eyes. He said that any manipulation in the eye, even phacoemulsification, depending on other risk factors, can also result in malignant glaucoma. Female patients are more likely to have this occur, as are eyes with a small anterior chamber and a small axial length, according to Dr. Schlenker. He added that there is mounting evidence that zonulopathy is a risk factor for malignant glaucoma. Dr. Varma said there is a risk for malignant glaucoma, in certain eyes, when anterior chamber shallowing occurs, for instance when you’re changing instruments in and out of the eye. “It causes the choroid to swell, and in a small eye, there is not much space for that swelling, so it pushes everything forward,” he said. “In a small eye, the normal mechanisms to reset, to balance between the front chamber and the back chamber, don’t work as well, so you end up unable to reverse it. The eye can’t recalibrate, and it progressively pushes everything forward. The back chamber and the front chamber get out of balance.” The physicians said that malignant glaucoma can occur intraoperatively or can develop over time postoperatively. Postoperatively, Dr. Varma said the lens will start to shift forward. “At day 1 the patient could look good, but at week 1 they’re a –1 or –1.5 myope because the lens has shifted forward, then they could be –3 or –4 by the end of the month; … they come back unhappy because now they’re nearsighted even more. Progressive myopia is not an IOL calculation problem; one needs to look deeper,” Dr. Varma said. Inas Aboobakar, MD, told EyeWorld that malignant glaucoma classically occurs in the early postop period after incisional glaucoma surgery in eyes with a history of angle Contact information Aboobakar: inas_aboobakar@meei.harvard.edu Schlenker: matt.schlenker@utoronto.ca Varma: devesh.varma@prismeye.ca Malignant glaucoma: Why it happens and its management by Liz Hillman Editorial Co - Director This article originally appeared in the September 2023 issue of EyeWorld. It has been slightly modified and appears here with permission from the ASCRS Ophthalmic Services Corp.
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