Face Masks May Reduce Endophthalmitis 

Laird Harrison

October 11, 2021

SAN ANTONIO — When everyone in the room wears face masks, patients may be less likely to get endophthalmitis during intravitreal injections, researchers say.

"We can't eliminate the risk, but we can reduce it," said Sunir Garg, MD, a professor of ophthalmology at Wills Eye Hospital, Thomas Jefferson University, in Philadelphia, Pennsylvania.

Though physicians and patients rarely wore masks for the procedure before the COVID-19 pandemic, the practice has become common as a way to prevent its spread.

Garg presented the finding here at the American Society of Retina Specialists (ASRS) 2021 annual meeting.

Previous research has suggested that bacterial dispersal is lessened when physicians wear masks or refrain from talking during intravitreal injections.

But other studies show that face masks on patients channel the patient's breath into the his or her eyes, potentially increasing the infection risk.

To see what effect mask-wearing had in relation to endophthalmitis, Garg and his colleagues retrospectively analyzed data from eyes receiving intravitreal anti-VEGF injections from October 1, 2019 to July 31, 2020 at twelve centers in the United States.

They divided the injections into two groups: 294,514 in which no one in the room wore a face mask and 211,454 in which everyone in the room wore a mask as a COVID-19 precaution. They counted the both the number of presumed cases of endophthalmitis and the number of cases in which endophthalmitis was confirmed by culturing bacteria.

Of the injections with no one in the room wearing face masks, 0.0289% resulted in presumed endophthalmitis, compared to .0213% of the injections with everyone in the room wearing face masks. That difference was not statistically significant (P = .097.)

But narrowing the comparison to confirmed, culture-positive endophthalmitis, the researchers found a rate of .0092% without masks and .0040% with face masks. This difference was statistically significant (P = .041).

"As a rule of thumb, face masks seem to be beneficial in reducing at least the culture-positive endophthalmitis," Garg told Medscape Medical News.

The researchers also compared endophthalmitis in which oral flora was cultured and found no significant difference in the two groups.

One challenge in the research is that endophthalmitis associated with intravitreal injections is so rare that it is hard to get a large enough dataset to make a statistically valid comparison, Garg said.

That made it hard to do sub-analyses. One potential sub-analysis involved injections in which the clinicians took the extra precaution of taping the tops of the masks to prevent the patients' breath from reaching his or her eyes. There were only 18,602 such injections with only 4 cases of endophthalmitis among them (.021%), so the researchers couldn't tell whether the taping made a difference.

In an attempt to answer that question, the same research group put petri dishes on the patients' foreheads to see if bacteria were flowing in that direction. They tried two scenarios: with the patients reading a script or sitting in silence. And they tried six types of masking: no face mask, loose-fitting surgical masks, tight-fitting surgical masks, tight-fitting surgical masks with tape, N95 masks, and cloth face masks.

They did not isolate any oral organisms when the subjects refrained from talking, but they isolated these organisms in 8 of 75 experiments (10.7%) when the subjects read the script.

They found that the N95 and taped masks were much more effective than the other types of mask in containing the bacteria.

"Adding tape to the top of the mask can potentially be clinically significant," said Samir Patel, MD, a fellow at Wills Eye Hospital, who presented the petri-dish study at ASRS.

The study should allay concerns that masking can cause endophthalmitis during intravitreal injections, he said. "Based on our data, we know that, at minimum, it doesn't increase, but it has a potential to decrease, the risk," he told Medscape Medical News.

But the case for masks is not completely closed, Garg said. Masks do have a cost, and the overall rate of endophthalmitis is low, he said. He's not sure whether he'll keep wearing a mask for intravitreal injections after the pandemic subsides.

John T. Thompson, MD, a moderator during Garg's presentation and an assistant professor at the Wilmer Eye Institute of Johns Hopkins University in Baltimore, Maryland, said the research has convinced him of the benefits of mask-wearing during intravitreal injections. "I think it's generally a good idea," he said.

Garg, Patel, and Thompson have disclosed no relevant financial relationships.

American Society of Retina Specialists. "The Influence of Universal Face Mask Use on Endophthalmitis Risk After Intravitreal Anti-VEGF Injections During the COVID-19 Pandemic" - COVID Symposium. Presented October 9 and 10, 2021.

Laird Harrison writes about science, health, and culture. His work has appeared in national magazines, in newspapers, on public radio and on websites. He is at work on a novel about alternate realities in physics. Harrison teaches writing at the Writers Grotto. Visit him at lairdharrison.com or follow him on Twitter: @LairdH

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