Ankylosing spondylitis (AS), a type of inflammatory arthritis that affects up to 1 percent of Americans, usually affects the lower back and pelvic area.

But it is often first suspected or initially diagnosed by an eye specialist — not by a rheumatologist. That’s because one of this condition’s complications is a kind of eye inflammation called uveitis, which could land you in an ophthalmologist’s chair.

"Uveitis is inflammation in the middle layer of the eye. If an eye doctor diagnoses uveitis in a young adult who also has back pain and stiffness, that is a big red flag for ankylosing spondylitis," says Brian Proctor, DO, an ophthalmologist at AMITA Health in La Grange, Illinois.

Uveitis causes the eyeball to appear red and bloodshot.

The Link Between Eye Inflammation and Ankylosing Spondylitis

As many as 50 percent of people with ankylosing spondylitis will develop uveitis at some point, according to the Spondylitis Association of America. This condition is considered a medical emergency, since it may lead to permanent damage or even blindness if left untreated.

“The most common type is uveitis in the front part of the eye, called anterior uveitis, or iritis,” says Dr. Proctor.

“Anyone with uveitis, or iritis, who also has joint pain, and has not been diagnosed with ankylosing spondylitis, should have imaging studies and a blood test to check for ankylosing spondylitis,” Proctor says.

Although the main symptoms of ankylosing spondylitis are joint pain and stiffness, it can cause inflammation in other parts of the body — including the heart, lungs, digestive system, and eyes.

Researchers have found certain genes to be common in both ankylosing spondylitis and uveitis. In an article published in January 2016 in the journal Ocular Immunology and Inflammation, the authors noted that people who develop uveitis — regardless of whether they have AS — and those with AS often share a genetic marker called HLA-B27, as well as others, including one called ERAP1. These genetic markers may interact in ways that lead to inflammation in different areas of the body.

Know the Symptoms of Uveitis

Uveitis is easier to treat if it is diagnosed early, says Proctor. Inflammation can be in one eye or in both eyes.

Here are the symptoms to watch out for, according to the Spondylitis Association of America:

Eye pain
Sensitivity to light
Eye redness
Blurred vision
Seeing spots in your vision

It’s important to see an eye specialist if you have symptoms of uveitis, because the diagnosis requires a special type of exam called a slit lamp examination, says Proctor.

During a slit lamp exam, an eye doctor will look through your pupil into the fluid that fills the inside of your eye. White blood cells floating in the fluid are the key to diagnosing uveitis.

With uveitis, “symptoms may go away without treatment, but they may also come back or get worse and cause complications, so it’s really important to let your doctor know right away if you have any signs of uveitis,” says Proctor.

Scarring from uveitis can cause the pupil to become fixed in place and may cause fluid to build up inside the eye — potentially leading to glaucoma, in which pressure builds up and damages the optic nerve, potentially leading to vision loss.

How Uveitis Is Treated

With proper treatment, uveitis symptoms should clear up in a few days, with the recovery time depending on how severe the inflammation is.

In some cases, topical drugs, taken as eye drops, are sufficient to treat uveitis. If not, systemic therapies, taken orally or by injection or infusion, are used.

According to an article published in The Permanente Journal, uveitis treatments include:

Steroid eye drops, to fight inflammation
Eye drops that dilate (widen) the pupil, to reduce pain
Periocular (around the eye) steroid injections
Steroids taken by mouth, for more severe cases
Systemic NSAIDs
Immunosuppressant drugs, for especially severe cases or those that don’t respond to steroids
Biologic therapies, including some of the same tumor necrosis factor (TNF) alpha-blockers that are used to treat ankylosing spondylitis itself
Dark glasses to protect your eyes

After you finish treatment for uveitis, you’ll need to be rechecked by an eye doctor — potentially several times — to make sure the condition hasn’t come back and to look for any scarring that may have occurred.

Strategies to Protect Your Eyes

"The most crucial tip is to always let your doctor know about any signs of eye inflammation,” says Proctor. “The first symptom is usually sensitivity to light — don't wait for other symptoms to develop."

The following general tips for eye health become especially important if you have a history of eye inflammation, or if you’ve already been diagnosed with ankylosing spondylitis:

Get an annual eye exam. But note that if you’ve been diagnosed with uveitis in the past, you may need to see an eye specialist more frequently than annually, says Proctor.

Wear protective eyewear. This guideline applies when you’re playing contact sports, using power tools, or if your workplace or leisure activities pose any risk to your eyes.

Wear sunglasses. Sunglasses that are designed to screen out 99 to 100 percent of ultraviolet rays should be worn on sunny days.

Give your eyes a break. When working in front of a monitor or screen, every 20 minutes, give your eyes a 20-second rest by looking 20 feet into the distance.

These precautions may not be enough to avoid uveitis, so it’s important to remain vigilant about any changes that occur.

“Ankylosing spondylitis is more common than people think, and so is uveitis,” says Proctor. “Both conditions can occur in otherwise healthy young adults. It’s important to seek treatment for these symptoms right away.”

Additional reporting by Quinn Phillips.