SAN ANTONIO, Texas – Hypochlorous acid causes less pain than povidone iodine when used as a disinfectant before intravitreal injections, researchers say.

Povidone iodine is the standard of care, but hypochlorous acid could offer a viable alternative, at least for patients who find povidone iodine intolerable, said Robert L. Avery, MD, of California Retina Consultants in Santa Barbara, Calif., Who does the Findings at the American Society of Retina Specialists (ASRS) Annual Meeting 2021.

“There’s no question that it’s less painful,” he told Medscape Medical News. “The only question is whether it will do the job.”

To compare the two treatments, Avery and colleagues recruited 62 patients and treated one eye with hypochlorous acid and the other eye with povidone iodine in each patient.

After instilling the disinfectant, the researchers asked patients to rate their pain on a scale of 1 to 10, with 10 being the worst pain the patients had ever felt. The researchers repeated the question immediately after the injection and 1-2 hours after the injection.

Table. Disinfectant pain


According to disinfectant, scale 1-10

Immediately after the injection, on a scale of 1-10

1-2 hours after injection, scale 1-10

Povidone iodine




Hypochlorous acid




P value




An hour or two after the procedure, 51 of the patients said the hypochlorous acid-treated eye was more comfortable than the povidone-iodine-treated eye. Neither said the povidone iodine-treated eye felt better, while eight said there was no difference and three did not respond. Thirty-nine reported a foreign body sensation in their eye with povidone iodine, versus three who said the same thing about their eye with hypochlorous acid.

The proportion of negative cultures was 68% with povidone iodine and 47% with hypochlorous acid. The difference was not statistically significant (P = 0.067) and none of the patients developed endophthalmitis, but the trend towards more negative cultures with povidone iodine raises concerns about hypochlorous acid, Avery said.

Previous studies have shown better disinfection results with increased use of povidone iodine drops; the same could be true of hypochlorous acid, Avery said. When used in their own practice on patients who cannot tolerate povidone iodine, Avery applies up to five times hypochlorous acid before and after applying an anesthetic seal.

A randomized controlled trial is underway to allow a more definitive comparison of the two disinfectants, Avery said.

Hypochlorous acid is an important potential addition to infection control tools for intravitreal injections, said Linda Lam, MD, MBA, professor of ophthalmology at the University of Southern California’s Roski Eye Institute at Arcadia. “It’s the aspect of the procedure that patients are most dissatisfied with,” she told Medscape Medical News.

Like Avery, she would need to see more research before she can use hypochlorous acid routinely. But she said it could be useful in patients who are unwilling to be re-treated after the povidone iodine sting. “There are a lot of patients who just don’t come back,” she said.

The study was funded by the California Retina Research Foundation. Avery reported on advising companies that make drugs for intravitreal injection. Lam has not disclosed any relevant financial relationships.

American Society of Retina Specialists: Comparing Hypochlorous Acid versus Povidone Iodine Pre-Intravitreal Injection: A Randomized Prospective Study (PAVE Study). Presented on October 9, 2021.

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

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