The GI-Eye Connection
If you’ve had Crohn’s disease for a while and it’s been you-don’t-even-know-how-long since you had an eye exam, read this report to see if it might be time.
Editor's Note: This story is part of a new series on HealthCentral called "Get Your Ph.D.!", which is geared toward people who've got the basics of their condition down and want to up their expertise. Who's ready to go pro?!
When you’re first diagnosed with a chronic condition like Crohn’s disease (CD), your focus is on dealing with the (literally) urgent symptoms at hand. After a while, most people find their new normal and with it, a new rhythm. But even when your CD is well-controlled, it’s crucial to stay on top of your care—especially when it comes to eye health.
Crohn’s disease may be a digestive disorder, but at least 1 in 10 people experience issues with their eyes, which range from mild pain and irritation to severe dryness and (less commonly) vision loss. In fact, when researchers gave inflammatory bowel disease (IBD) patients an eye exam, they found previously undiagnosed conditions in a whopping 92% of them, according to a small study published in the European Journal of Gastroenterology & Hepatology. Despite finding like this, there are no routine screening guidelines or recommended eye exams for any inflammatory bowel disease, which includes Crohn's and ulcerative colitis, says Sumitra Khandelwal, M.D., assistant professor of ophthalmology at Baylor College of Medicine in Houston.
While we don’t know exactly why Crohn's sometimes causes complications in the eyes, the current thinking is this: The inflammation in your digestive tract is your body’s reaction to gastrointestinal antigens (toxins or other foreign substances that initiate an immune response in the body). Some of the antigens in your eyes are like those in your GI system. Once these antigens are recognized, the body attacks them, too, creating another type of autoimmune reaction, explains Benjamin Bert, M.D., ophthalmologist at MemorialCare Orange Coast Medical Center in Fountain Valley, CA.
Alternatively, some researchers believe certain immune complexes (a.k.a. molecules that form when an antigen and antibody bind together) from the gut could be absorbed and travel through the bloodstream, where they're then deposited in the blood vessels of the eyes, causing inflammation.
Either way, we know that any ocular complication from a systemic inflammatory disorder like Crohn’s can damage your vision and the structure of your eye if not identified and treated swiftly. And while every patient who's been living with IBD should be aware of these potential problems—and see your optometrist and/or ophthalmologist regularly—it's particularly important for women, anyone diagnosed with Crohn's before age 40, and those with a family history of Crohn's or UC, says Dr. Bert. These groups tend to be a higher risk for eye problems.
Our guide to the most common Crohn's-related eye issues can help you stay one step ahead.
What it is: The condition causes inflammation in the layer between the conjunctiva (that’s the clear layer on top of the white of the eye) and the sclera (the white tissue of the eye). Among all the eye complications, episcleritis is tied to Crohn’s inflammation the most, according to a study analysis in the World Journal of Gastroenterology. That means if your inflammation levels are high, your eyes are going to feel it. But getting the underlying IBD under control will help improve the symptoms, Dr. Bert adds.
Symptoms and possible complications: Episcleritis is a benign condition and most symptoms are limited to mild pain and irritation of the eye. It doesn't cause permanent damage.
How it’s treated: Most of the time, docs will treat episcleritis with just observation as they continue to treat the systemic inflammation of the disease, Dr. Bert says. In some cases, lubricating eye drops can help soothe the discomfort. Corticosteroid eye drops may also be prescribed for short-term use but should never be used long term because of the potential for complications like cataracts or glaucoma.
Dry Eye Disease
What it is: Dry eye disease is three times higher in people with inflammatory bowel disease compared to people without, according to a study published in Eye & Contact Lens. But folks with Crohn's specifically are the most likely to develop dry eye disease compared to those with other types of digestive inflammation, according to Hungarian research. Here’s why:
Dry eye disease typically stems from the malabsorption of nutrients, which comes with the CD, Dr. Bert explains. People with Crohn's have a harder time absorbing water, vitamins, and minerals. As a result, they have a harder time producing enough liquid for tears, and the tears they do produce may evaporate more quickly, creating the symptoms of dry eye.
Symptoms and possible complications: The most common symptoms are dryness (of course), blurry vision, aching, and a scratchy sensation. If dry eyes become chronic or severe, they can affect new blood vessel growth or scar the surface of your eye, both of which can lead to poor vision.
How it’s treated: Treating the underlying inflammation of Crohn's and using daily artificial tears are the most common way to treat dry eye, but many docs also recommend adding moisture to the environment with humidifiers and warm compresses over the eyes. Your doctor may also recommend eye drops like a weak corticosteroid or cyclosporine to relieve inflammation and increase tear production.
What it is: Keratopathy is a rare manifestation of Crohn’s that usually develops from extreme dry eye disease. With less moisture coating the eyes, this can create a situation where the eye becomes so dry that it creates its own type of inflammation, Dr. Bert explains.
Symptoms and possible complications: Surprisingly, keratopathy doesn't create any pain or vision issues, so it's super hard to diagnose. An ophthalmologist must be looking for it specifically, using a special slit lamp to spot white deposits at the edge of the cornea. Doctors don't know what the dots are exactly—there are no known biopsies of the lesions, reports a paper in The Scientific World Journal. But we do know that since they typically occur at the corners of your cornea, they often spare your central vision.
How it’s treated: Overall, keratopathy doesn't usually cause serious damage and often resolves on its own (that is, the best treatment is systemic immunosuppressives for the underlying Crohn's). However, if the inflammation, and therefore keratopathy, is left untreated, it can advance and become bothersome to the point that it may need to be treated with calcium-binding eye drops or (last resort) an in-office procedure where the doctor scrapes the deposits off the surface of the cornea.
What it is: Uveitis is inflammation within the eyeball itself and is the most dangerous of all eye complications because it progresses quickly and can lead to permanent vision loss. “Typically, the inside of the eye is protected by a blood-aqueous barrier, which prevents blood cells from entering the fluid inside of the eye. With the inflammation created by the autoimmune condition, this barrier breaks down and components of the blood can enter the fluid within the eye,” Dr. Bert explains. That's bad news because it leads to inflammation and swelling that destroys eye tissue. It's a more common ocular complication, but it mostly manifests in people with severe Crohn's disease, according to a 2019 meta-analysis in Therapeutic Advances in Gastroenterology.
Symptoms and possible complications: The breakdown of the blood-aqueous barrier and, therefore, the release of blood into the eye creates symptoms like redness, light sensitivity, pain, blurry vision, and floaters, Dr. Khandelwal adds. The real risk comes with complications though: Inflammation in the eye can lead to tiny lesions, which in turn cause vision-impairing scar tissue to develop. It can create elevated eye pressure, which can lead to cataract formation. Or it can contribute to retinal swelling called macular edema, or even glaucoma (a break down of the eye's optic nerve), both of which can cause irreversible loss of vision, Dr. Bert adds.
How it’s treated: Unlike the other conditions, uveitis doesn’t necessarily follow the activity level of Crohn's disease itself. Instead of focusing on the underlying inflammation to treat it, the condition typically requires topical steroids, then systemic immunomodulators (meds that help regulate your immune system, like methotrexate and azathioprine) if it becomes chronic, Dr. Bert explains.
Interestingly, emerging research suggests dysfunction in your gut microbiome may come into play. A study by researchers in India, for example, found that people with uveitis were more likely to have dysbiosis (a microbial imbalance in the body) compared to people without the condition. Early stage research by the NIH found that mice who were genetically engineered to eventually develop uveitis had higher levels of activated T-cells (your immune cells that penetrate that blood-aqueous barrier and cause the problems) specifically in the gut.
When the mice were given meds to clear out their gut bacteria, including the activated T-cells, they didn't develop uveitis till much later and with less severity. Researchers are therefore starting to consider fecal transplants (yep, that’s poop in a pill) for people with uveitis to help reset sufferer’s microbiome.
Give the Eye Doc a Full Picture
Although most complications in the eye are treatable, research shows the symptoms may be easily overlooked by your doc, so it's super important to tell your optometrist that you have Crohn's disease.
Outside of the complications mentioned here, inflammatory bowel disease can cause other, peripheral issues: For example, a recent study in Seminars in Ophthalmology found that those with IBD (either Crohn's or ulcerative colitis) have thinner corneas compared to those without the inflammatory disease. Other research has shown that having a thin cornea can lead to "artificially low" readings when doctors measure your eye pressure. That could lead to possibly missing a glaucoma diagnosis, a condition that can permanently damage your vision when left untreated, according to the Glaucoma Research Foundation.
Another thing to remember: You can have eye complications even if it appears your Crohn’s is under control, Dr. Bert adds. Even if levels of blood inflammation are low enough that they won’t manifest as your typical Crohn’s symptoms, there are some eye conditions that are related to side effects of treatment. For instance, long-term use of corticosteroids (often used for inflammation) is associated with a higher risk of getting cataracts and specific types of keratopathy.
In some cases, if you’ve developed ocular complications while wrangling your Crohn’s, those issues tend to stick around and need to be treated once the inflammation is controlled, he explains. “Any symptoms of redness, pain, light sensitivity or decreased vision in a patient who has Crohn’s deserves to be worked up and examined,” says Dr. Bert.
Prevalence of Eye Complications: Crohn’s and Colitis Foundation. “Eye Complications.”
IBD and Undiagnosed Eye Complications: European Journal of Gastroenterology & Hepatology. (2018). “High frequency of secondary, but not primary ocular manifestations of inflammatory bowel disease in patients treated at a tertiary care center.” https://pubmed.ncbi.nlm.nih.gov/30148806-high-frequency-of-secondary-but-not-primary-ocular-manifestations-of-inflammatory-bowel-disease-in-patients-treated-at-a-tertiary-care-center/
IBD Eye Issues: Korean Journal of Gastroenterology. (2019). “Ophthalmologic Manifestation of Inflammatory Bowel Disease: A Review.” ncbi.nlm.nih.gov/pubmed/31132833
Eye Complications with IBD: Scientific World Journal. (2015). “Ocular Complications of Inflammatory Bowel Disease.” ncbi.nlm.nih.gov/pubmed/25879056
Study Analysis of Ophthalmic Manifestations with IBD: World Journal of Gastroenterology. (2017). “Ophthalmic Manifestations in Patients with Inflammatory Bowel Disease.” ncbi.nlm.nih.gov/pubmed/28932076
Tear Film Study: Eye Contact Lens. (2018). “Conjunctival Impression Cytology and Tear-Film Changes in Patients with IBD.” ncbi.nlm.nih.gov/pubmed/30005056
Dry Eye Research: Biomed Research International. “Evaluation of Objective Signs and Subjective Symptoms of Dry Eye Disease in Patients with IBD.” ncbi.nlm.nih.gov
Uveitis and IBD Info: Therapeutic Advances in Gastroenterology. (2019). “Uveitis Manifestations in Patients of the Swiss Inflammatory Bowel Disease Cohort Study.” ncbi.nlm.nih.gov
Thin Corneas and IBD: Glaucoma Research Foundation. (2017). "The Importance of Corneal Thickness."