tA probiotic bacterial strain may help with dry eye, a study in mice suggests. Image credit: Jonathan Knowles/Getty Images.
- About 12% of the global population has dry eye, a condition in which the eyes are unable to self-lubricate sufficiently.
- There is currently no cure for dry eye disease.
- Researchers from Baylor College of Medicine in Houston, TX have identified a probiotic bacterial strain that helped improve dry eye via a mouse model.
Almost 12% of the entire world’s population has dry eye, a condition where the eyes do not make enough tears to keep them properly lubricated, causing discomfort.
Although there is currently no cure for dry eye disease, there are a number of treatments available to help treat the condition’s symptoms.
These treatments include over-the-counter eye drops, prescription medications, or procedures such as the addition of punctal plugs in the eye’s tear ducts.
Now, researchers from Baylor College of Medicine in Houston, TX have identified a probiotic bacterial strain that helped improve dry eye via a mouse model.
This research was recently presented at ASM Microbe 2023, the annual meeting of the American Society for Microbiology.
What is dry eye?
While people may associate tears with crying, healthy eyes actually produce tears all the time. As a person blinks, these tears — known as the tear film — are distributed over the surface of the eye to provide lubrication, remove any foreign particles, and protect the eyes from infection.
Sometimes a person’s eyes may not make enough natural tears, causing dry eye disease. This can happen for a number of reasons, including:
- a dysfunction in the tear film
- tears that evaporate too quickly
- age over 50 years
- taking certain medications, such as antihistamines
- environmental issues including smoke, wind, and dry climate
- eyelid disfiguration
- extended contact lens use
- having certain diseases, including Sjögren’s syndrome, lupus, rheumatoid arthritis, diabetes, or thyroid disorders.
Symptoms of dry eye disease include:
- burning, stinging, or scratchy feeling in your eyes
- feels like something is in your eye
- mucus in or around the eyes
- light sensitivity
- red or irritated eyes
- difficulty wearing contact lenses
- blurred vision
- excessively watery eyes.
If undiagnosed and untreated, dry eye can cause eye infections and potential damage to the surface of the eye known as the cornea. If corneal damage becomes severe, it can even lead to vision loss.
Dry eye and the gut
In addition to medical treatments for dry eye, previous research shows that dietary changes may help combat the condition.
A study in 2019 found that omega-3 supplements significantly improved dry eye symptoms and signs in people with dry eye disease.
Another study in 2019 reported short-term vitamin A supplementation helped improve the quality of tears in people with dry eye disease.
According to Dr. Laura Schaefer, assistant professor of molecular virology and microbiology at Baylor College of Medicine in Houston, TX, and lead author of this study, it is important to look for new treatments for dry eye.
“Despite the prevalence of dry eye — approximately 1 in 20 people in the U.S. — there are only a handful of drugs currently available to treat dry eye, and for some patients, these drugs do not work very well to improve symptoms,” she told Medical News Today.
Dr. Schaefer said she and her team decided to focus on looking at a probiotic bacterial strain in the gut to treat dry eye because their previous work showed a functional link between gut bacteria and dry eye disease symptoms.
“We performed several experiments using gut bacteria isolated from Sjögren syndrome patients who have severe dry eye, from healthy patients with no eye disease,” she detailed. “When mice are colonized with Sjögren patient gut bacteria, they develop worse dry eye under dry conditions than mice colonized with gut bacteria from healthy patients.”
“This suggests that the gut bacteria from healthy people protect the surface of the eye in dry conditions, and therefore one possible treatment avenue for dry eye would be probiotic bacteria that have similar protective effects,” Dr. Schaefer added.
Examining probiotic bacteria for dry eye
For this study, Dr. Schaefer and her team utilized a mouse model of dry eye. Mice were first given an antibiotic to kill off “good” bacteria in the gut. They were then exposed to very dry conditions and given either the probiotic bacterial strain, Limosilactobacillus reuteri DSM17938, or a saline solution as a control.
After 5 days, scientists found the mice given the probiotic bacterial strain had healthier and more intact corneal surfaces than those given the saline solution.
Additionally, the mice fed the probiotic bacteria also had an increased amount of goblet cells in their eye tissue. Goblet cells are cells that produce an essential component of tears called mucin.
“Our hypothesis was that the probiotic would be protective of the eye, and it was exciting to prove that is true,” Dr. Schaefer said. “This particular probiotic strain, DSM17938, has been well-studied and shown to lower inflammation in other tissues, notably the gut, and improve intestinal barrier function. It has not, however, been evaluated before in the context of the eye.”
“These findings show that bacteria with anti-inflammatory effects in the gut can also reduce inflammatory conditions in the eye. It is known that a healthy diet that is low in harmful fats and high in fiber feeds the ‘good’ bacteria that live in our guts naturally, and the anti-inflammatory effects of these bacteria in the gut can extend to other tissues in the body, including the eye.”
– Dr. Laura Schaefer
Future treatment abilities
MNT also spoke with Dr. Benjamin Bert, an ophthalmologist at MemorialCare Orange Coast Medical Center in Fountain Valley, CA, about this study, in which he was not involved.
“It was actually a pretty fascinating study to see the multi-components that are involved with both our understanding of dry eye and then also our future abilities to treat dry eye,” he commented.
We had seen previously that taking supplements — omega-3 supplements, for example — [was] shown to be beneficial for treating patients with certain types of dry eye. So looking more at the gut microbiome as a potential treatment point is fascinating,” Dr. Bert added.
As for the next steps in this research, he said that as this was conducted via a mouse model, a study in humans would be needed.
“It would be really interesting to see this used as a supplement in a human trial to really prove what their hypothesis is, of this being a significant benefit or a possible treatment that could be used for patients with dry eye,” he added.
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