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The link between eye conditions and gut health

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Gut health and your eyes

Good gut health starts with your gut microbiome. In fact, your digestive system contains trillions of bacteria, fungi, yeast and viruses that play a key role in maintaining healthy digestion. They also have a major impact on the health of the rest of your body – including your eyes.

Uveitis and your gut

New studies have found a clear connection between gut and eye health in mice that could lead to breakthroughs in the treatment of eye inflammation. This five-year project, funded by a grant from the National Eye Institute, aims to find new medications to treat uveitis.

Uveitis is inflammation of the middle layer of the eye, which consists of the iris, ciliary body and choroid. If uveitis becomes chronic, it can lead to other serious eye problems, such as cataracts, glaucoma, retinal detachment and vision loss. It is now often treated with corticosteroids.

The new research on uveitis and the gut at Oregon Health & Science University shows that the severity of chronic noninfectious uveitis in mice is linked to having fewer regulatory T cells in the gut. These specialized cells, also called "Tregs," help control and prevent inflammation. Scientists at OHSU found that giving mice antibiotics or short-chain fatty acids helped to both: 

  • Increase the number of Tregs in the gut and

  • Lower the amount of inflammation in the eyes

Scientists who have studied uveitis patients have found that they tend to have microbiomes that are different from healthy control subjects. For example, uveitis patients may have:

  • Less diversity in their gut microbiome

  • Fewer anti-inflammatory microbes in their gut

This doesn't necessarily mean that these differences cause uveitis, and researchers are continuing to look for more answers. On a similar track, studies are also being done to determine if uveitis patients benefit from having their gut imbalances corrected with immunomodulatory therapy.

Gut health, overall health and your eyes

Poor gut health can lead to a variety of problems, including issues with your eyes. Some signs of poor gut health may include:

  • Digestion issues (bloating, constipation etc.)

  • Dry eyes and other eye problems

  • Fatigue

  • Mood changes

  • Skin problems (rashes, etc.)

  • Sleep issues 

All these issues can be caused by other health problems, some of which may be serious. So it's important to see your family doctor and your eye doctor for any unexplained symptoms. Your doctor can help you rule out other issues and give you advice on improving your gut health.

Dry eyes

Dry eyes occur due to problems with the tear film on your eyes. A normal tear film consists of three components: oils, mucus and water. The tear film plays a key role in keeping your eyes moist and comfortable. Symptoms of dry eyes may include blurry vision, redness, light sensitivity (photophobia) and eye fatigue.

The microorganisms in the gut may also play a part in whether dry eye symptoms are developed. As with age-related macular degeneration, more research is needed to offer better answers in this area. But one study found that mice raised in a germ-free environment with no gut microbes developed extremely dry eyes. When the mice began living with normal mice and acquiring their gut microbes, their dry eye symptoms improved.

Age-related macular degeneration 

Age-related macular degeneration (AMD) affects the macula, a part of the retina that is key for good vision. In fact, macular degeneration can lead to vision loss, causing blurriness or shadowy spots in the center of your field of vision. 

Doctors don't fully understand the relationship between AMD and gut health, though research in mice suggests there is a connection. For example, it’s possible that an imbalance in the gut microbiome may cause inflammation that can affect the development and progression of macular degeneration.

In one study, mice that were fed a sugary diet developed degenerative changes in their eyes that could be reversed by changing their diet. Additionally, the gut microbiome may play a role in the effectiveness of antioxidant supplementation in slowing the progression of AMD in humans.


Glaucoma is an eye condition caused by increased pressure in the eyes. It's important to detect and treat glaucoma early as it can damage the optic nerves, which send signals between the eyes and the brain. If not caught early, glaucoma can lead to permanent vision loss.

Numerous studies have found links between gut microbiota and glaucoma, but more research is needed to find out if and how the microbes in the gut may affect the development and progress of glaucoma.

Researchers have also begun to look at possible links between oral microbiota and glaucoma. Still a relatively new area of research, scientists have so far found that glaucoma patients had much higher levels of oral bacteria than people without glaucoma. 

Good habits for gut health

There is still much research left to be done on the links between gut health and eye health. In the meantime, there are general steps you can take for a healthier gut that could have a positive impact on your eyes.

Follow these tips for good gut health, and you may also help protect your eyes:

  • Avoid unnecessary antibiotics. While antibiotics can be lifesavers when necessary, antibiotic overuse can lead to gut issues by killing good bacteria. 

  • Eat well for eye and gut health. Cut back on simple sugars, refined grains and fried foods such as bagels, donuts and sugary sodas. Add more whole foods: colorful fruits and vegetables, leafy greens, beans and whole grains. Eating an eye-healthy diet can benefit your gut and your eyes.

  • Try adding fermented foods to your diet. Experiment with fermented foods, such as yogurt, kefir, kimchi, kombucha and sauerkraut, that may benefit your gut.

If you have specific eye health concerns, talk to your eye doctor about other steps you may take. For example, some patients may benefit from taking probiotics or vitamin supplements for the eyes. It's also important to make sure you get a regular comprehensive eye exam, which is one of the most important steps you can take to keep your eyes healthy.

READ NEXT: 8 things your eyes can reveal about your health

The gut and the eye. American Academy of Ophthalmology. October 2020.

Pathway to better eye health runs through the gut. Oregon Health & Science University. December 2021.

Uveitis. National Eye Institute. November 2021.

Oral microbiome link to neurodegeneration in glaucoma. PLoS One. September 2014.

Microbiota and ocular diseases. Frontiers in Cellular and Infection Microbiota. October 2021.

Signs of poor gut health. Piedmont Healthcare. Accessed March 2022.

What is macular degeneration? American Academy of Ophthalmology. February 2022.

Dry eye. American Optometric Association. Accessed March 2022.

Sjögren-like lacrimal keratoconjunctivitis in germ-free mice. International Journal of Molecular Sciences. February 2018.

Glaucoma. National Eye Institute. September 2021.

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