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Researchers studied the magnitude of bacterial load reduction on the surface of the skin 20 minutes after application of saline containing 0.01% pure hypochlorous acid as the preservative to the skin below the lower eyelid.
Take-home message: Researchers investigate the magnitude of bacterial load reduction on the surface of the skin 20 minutes after application of saline containing 0.01% pure hypochlorous acid as the preservative to the skin below the lower eyelid.
Reviewed by Arthur B. Epstein, OD
Phoenix-An eyelid wash preserved with pure hypochlorous acid (Avenova with Neutrox, NovaBay Pharmaceuticals) can significantly reduce the bacterial load on the surface of the eyelid.
Reducing the bacterial load can help reduce the signs and symptoms of dry eye, meibomian gland dysfunction (MGD), and other and other conditions related to bacterial overgrowth.
“I have been using this cleaner with some of my dry eye patients who had significant lid crud, inflammation, and discomfort,” said dry eye specialist Arthur B. Epstein, OD, founder of Phoenix Eye Care and the Dry Eye Center of Arizona. “The results are disruptive. Patients see and feel the improvement in a day or two.”
Before (left) and after (right) images of reduced bacterial load on surface of patient’s eyelid treated with the eyelid wash preserved with pure hypochlorous acid. (Photos courtesy of NovaBay Pharmaceuticals)
Dr. Epstein was third author on a study that examined the clinical impact of the 0.01% solution of hypochlorous acid.
“We had good data that hypochlorous acid kills bacteria very rapidly in vitro,” added lead author David Stroman, PhD, senior vice president of ophthalmology development for NovaBay Pharmaceuticals. “We wanted data on how quickly bacteria would be removed on the eyelid in a clinical setting with patients who had significant lid inflammation.”
Response in clinical setting
Microbiological specimens were taken before treatment and 20 minutes after treatment from both eyelids of 36 patients. Of the 72 specimens collected, 71 were processed. Most of the patients, 22, were women and the average age was 63 years.
The results were both startling and clinically important, Dr. Epstein said.
A single treatment significantly reduced the overall bacterial population on the eyelid but had little impact on the bacterial species diversity.
“The effect of bacterial overload on blepharitis and meibomian gland dysfunction has not been appreciated until recently,” Dr. Epstein said. “I had never seen this kind of response before.”
Most lid disease is the result of two related-but-distinct pathologies, he explained. As MGD progresses, the character and the amount of oil produced by the glands changes. They produce less meibomian, which becomes thicker and more saturated. This promotes increases in bacteria on the lid leading to overpopulation.
One pathology is a direct byproduct of bacterial competition as populations overgrow. Bacteria produce a number of inflammatory proteins to combat each other which can inflame host tissue. In the ocular environment, bacteria produce an abundance of enzymes including lipase, which breaks down the lipid layer in the tear film.
As the lipid layer breaks down and mixes with salt in the tears, saponification produces the frothy soapsuds often seen on the lid margin and in tears. These soaps are both irritating and further break down the lipid component that protects and stabilizes the tear film.
Polar, nonpolar phases
The oil layer of the tear film has two phases, polar and nonpolar, Dr. Epstein continued.
The polar phase bonds the nonpolar phase to the underlying aqueous layer while the nonpolar layer forms an evaporative barrier and provides structural stability. As lipase breaks down the lipid layer, it also mechanically destabilizes the tear film.
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“Bacterial overgrowth gives the eye a double whammy,” he said.
Lipase produced by the bacteria as a result of their overgrowth and competition breaks down the lipid layer. The soaps produced by the lipid breakdown also break down whatever lipid remains, creating an alternative pathway for tear film instability and dry eye, according to Dr. Epstein.
Before and after two weeks of treatment with the hypochlorus acid wash. Courtesy of NovaBay Pharmaceuticals“Hypochlorous acid not only knocks down the bacterial overgrowth that triggers overproduction of lipase, it almost totally shuts down lipase activity and halts that degradation of lipids that destroy the tear film,” he said. “We have never had a treatment for dry eye or blepharitis with this mechanism of action or a treatment this effective.”
Resistance to hypochlorous acid does not appear to be a problem, he continued.
Hypochlorous acid is the bactericidal element used by macrophages and other components of the innate immune system to directly destroy invading microbes. Where traditional antibiotics use subtle mechanisms, such as interference with cell wall synthesis, DNA gyrase, topoisomerase 4 DNA replication or other pathways that can be circumvented, hypochlorous acid directly attacks and kills pathogens.
“No one product works for every patient, although this is almost universal for meibomian gland dysfunction, dry eye, and blepharitis,” Dr. Epstein said.
“More importantly, hypochlorous acid is neutralized so quickly that it doesn’t kill all the bacteria,” he said. “It just helps reduce bacterial populations to more normal levels. You don’t want a population of pseudomonads moving in on the lid because all of the staphylococci have been killed off.”
The next step in the clinical program is to examine changes in bacterial populations and diversity after a normal course of treatment.
The product is used twice daily for 10 to 14 days for acute treatment. However, most patients continue use indefinitely.
Preliminary indications suggest changes similar to the 20-minute sample, Dr. Stroman said, but a controlled trial is needed.
“It is easy to look at the in vitro data and say hypochlorous acid removes everything, but the reality is that it does not sterilize the skin,” Dr. Epstein said. “You can’t practically sterilize the skin in the clinical setting and you don’t want to. But you can reduce the bacterial load on the lid surface and that makes a phenomenal difference to your patients.”
Arthur B. Epstein, OD
This article was adapted from a presentation by lead author David Stroman, PhD, senior vice president of ophthalmology development for NovaBay Pharmaceuticals, at the 2016 meeting of the Association for Research in Vision and Ophthalmology.