How and whether microorganisms in the human gut cause a variety of diseases is a hot topic among medical researchers.
Now, a pilot study led by ophthalmologist Sanjay Kedhar, MD, director of UCI Health’s Ocular Immunology and Uveitis Service, hopes to learn how gut bacteria may instruct immune cells to attack the eye, creating an inflammation called uveitis.
Risks of untreated uveitis
Uveitis is actually the name for more than 50 different autoimmune diseases that attack the middle layer of the eye. This rare condition — it affects fewer than 200,000 people in the United States each year — causes:
Very severe uveitis can lead to blindness.
Mild cases of uveitis can be treated with eye drops or antibiotics, but when infection elsewhere in the body is the cause, severe uveitis cases must be treated with powerful steroids and immunosuppressive drugs.
It’s with these infections that Kedhar suspected a connection between human gut bacteria and uveitis, a link that previously had only been observed in animal experiments.
Drawing an antibiotic link
Sometimes medications, themselves, may make patients susceptible to various infections, says Kedhar, associate professor of ophthalmology at UCI School of Medicine’s Gavin Herbert Eye Institute.
And when those infections are treated with antibiotics, some patients who also suffer from uveitis see their eye inflammation disappear.
“One woman we’ve been treating for an autoimmune disease that caused a chronic inflammation of the eye has had no recurrence two years after receiving antibiotics,” he says.
Kedhar suspects the antibiotics killed the gut bacteria responsible for attacking the eye tissue. In the pilot study, he and his researchers will take samples of the microorganisms living in the guts of patients with uveitis to try to draw a link.
The study, which is just getting underway, will benefit from the relatively large number of uveitis patients who seek specialized care at the eye institute. Kedhar sees about 100 to 120 uveitis patients each month.
“If we can establish certain patterns in the bacteria we see, the implication may be that we’ll be able to treat these uveitis patients without immunosuppression drugs,” Kedhar says. “Our ultimate goal would be to treat it through diet and probiotics.”
Hard evidence needed
Although the connection has not yet been proven between gut bacteria and uveitis, studies like Kedhar’s are gaining steam across the country. He predicts that something definitive will be known within the next five years.
Should people start taking probiotics now as a precaution? Not so fast, Kedhar says, because we lack hard evidence that they work to prevent or cure uveitis. Others also theorize that other measures, including eating a high-fiber diet, may also be helpful in reducing eye inflammation. More study is needed in both areas, he says.
In the meantime, Kedhar advises people to consider how diet, exercise and sleep can affect their immune system and their health.
Learn more about the eye-gut connection
Kedhar will discuss his research on the gut microbiome's role in eye disease in a free lecture Sept. 24 at the Newport Beach Central Library, 1000 Avocado Ave., Newport Beach, CA 92660. Doors open at 6:30 p.m. His talk begins at 7 p.m.