Uveitis is inflammation inside the eye, specifically in the middle layer of the eye wall called the uvea. It affects roughly 234 out of every 100,000 people in the United States, with about 52 new cases per 100,000 diagnosed each year. While it can strike at any age, uveitis is a leading cause of preventable vision loss because the inflammation can damage surrounding eye structures if left untreated.
The Uvea and Why It Matters
The uvea is the middle layer of your eye’s wall, sandwiched between the tough outer shell (sclera) and the light-sensitive retina at the back. It’s made up of three connected structures, each with a distinct job:
- Iris: The colored ring of muscle at the front of your eye that widens and narrows to control how much light gets in.
- Ciliary body: A ring of tissue just behind the iris. Its muscles change the shape of your lens so you can focus on objects at different distances. It also produces the fluid that fills the front of your eye and helps maintain its shape.
- Choroid: A thin sheet of tissue densely packed with blood vessels, wrapping around the back of the eyeball. It supplies oxygen and nutrients to the retina and absorbs stray light to keep your vision sharp.
Because the uvea is rich in blood vessels, it’s especially vulnerable to inflammation. Immune cells traveling through the bloodstream can easily reach these tissues and trigger a response there.
Types Based on Location
Uveitis is classified by which part of the uvea is inflamed, and the location determines both the symptoms you experience and the potential complications.
Anterior uveitis affects the front of the eye, primarily the iris. It’s the most common form and typically causes a red, painful eye along with light sensitivity and blurred vision. It can come on suddenly in one eye, though autoimmune-related cases sometimes affect both.
Intermediate uveitis involves the ciliary body and the gel-like substance (vitreous) in the middle of the eye. It usually isn’t painful but often produces floaters and blurry vision.
Posterior uveitis targets the choroid at the back of the eye, near the retina. Because of that location, the main symptom is worsening vision or changes in your visual field rather than redness or pain.
Panuveitis means inflammation is present throughout all layers of the uvea at once. It tends to combine symptoms from all three types and generally carries the highest risk of complications.
What Causes It
The vast majority of uveitis cases are noninfectious, driven by an overactive immune system. In the U.S., noninfectious uveitis has an incidence of about 51 per 100,000 people per year, compared to roughly 15 per 100,000 for infectious cases.
Autoimmune and Systemic Conditions
Many cases are linked to autoimmune diseases that affect other parts of the body. A genetic marker called HLA-B27 is one of the strongest associations: in one study of HLA-B27-positive uveitis patients, 58% had a related systemic condition such as ankylosing spondylitis or another inflammatory spine and joint disorder. Notably, nearly half of those patients were diagnosed with their systemic condition only after seeing an eye doctor for uveitis. Sarcoidosis, an inflammatory disease that causes clusters of immune cells to form in different organs, is another common trigger. Other linked conditions include inflammatory bowel disease, psoriatic arthritis, and reactive arthritis.
Infections
Viruses, bacteria, and parasites can all cause uveitis directly. Herpes simplex virus and varicella-zoster virus (the virus behind chickenpox and shingles) account for about 8% of uveitis cases in some populations. Syphilis is a well-known bacterial cause, with uveitis occurring in up to 5% of people with late-stage syphilis. Tuberculosis is another bacterial trigger seen worldwide. Among parasitic causes, toxoplasmosis stands out. It represents about 25% of posterior uveitis cases in the U.S. and up to 85% in countries like Brazil where the parasite is more prevalent.
In many cases, no specific cause is identified. These are labeled “idiopathic,” meaning the inflammation is real but the trigger remains unknown.
How It’s Diagnosed
An eye doctor typically starts with a standard vision check and a look at how your pupils respond to light. From there, the key tool is a slit-lamp exam, a specialized microscope that shines a thin, intense beam of light into your eye. This lets the doctor see individual inflammatory cells floating in the fluid at the front of the eye, which is the hallmark sign of anterior uveitis.
To evaluate the back of the eye, your pupils are dilated with drops so the doctor can examine the retina and choroid directly. If inflammation is suspected deeper in the eye, additional imaging may follow. Optical coherence tomography (OCT) creates detailed cross-sectional maps of the retina and choroid, revealing swelling that might not be visible otherwise. Specialized dye-based imaging can highlight leaking or swollen blood vessels inside the eye.
Because uveitis is so often tied to a systemic condition, your eye doctor may order blood tests or imaging of other body parts (chest X-ray, CT, or MRI) to look for an underlying cause. In some cases, a small sample of fluid from inside the eye is analyzed to check for specific infections.
Treatment Approach
The primary goal is to suppress the inflammation before it damages the eye’s internal structures. Treatment follows a “stepladder” approach, starting with the least aggressive option and escalating if needed.
For most people, the first step is corticosteroid eye drops, which control inflammation locally without affecting the rest of the body. When inflammation is deeper in the eye or more severe, steroid injections directly into or around the eye deliver medication right where it’s needed. Some implantable devices placed inside the eye release a low dose of steroids continuously for up to three years, which is useful for people with chronic posterior uveitis who would otherwise need frequent treatments.
If steroids alone can’t control the disease, or if someone needs to be on steroids long-term, the next step is an immune-modifying medication taken by mouth. These work by dialing down the overactive immune response that’s fueling the inflammation. The goal is typically to reduce oral steroid use to the lowest possible dose to avoid side effects like weight gain, bone thinning, and elevated blood sugar.
For cases that don’t respond to those conventional options, biologic medications that target specific parts of the immune signaling chain are available. These are given as injections under the skin or through an IV, usually on a regular schedule every few weeks. Infectious uveitis, of course, requires treating the underlying infection directly with the appropriate antiviral, antibiotic, or antiparasitic medication.
Recurrence and Long-Term Outlook
One of the most frustrating aspects of uveitis is that it tends to come back. Even among people experiencing their first episode of acute anterior uveitis who achieve a full, medication-free remission, about 39% relapse within a year and a half. The relapse rate is roughly 24% per person-year. People who carry the HLA-B27 marker, especially those who also have a spondyloarthropathy, face an even higher risk of repeated flares.
Chronic or frequently recurring uveitis can lead to serious complications over time. Macular edema, swelling of the central retina that blurs fine detail vision, is one of the most common. Glaucoma can develop when inflammation or steroid treatment raises the pressure inside the eye. Cataracts form earlier and more frequently in people with uveitis, and even after cataract surgery, complications are more common in this group: one study found that over 60% of eyes with uveitis experienced at least one complication in the months following surgery, with clouding behind the new lens and macular edema being the most frequent.
Despite these risks, most people with uveitis retain useful vision when inflammation is caught early and managed consistently. The key factor is staying on top of follow-up appointments so flares can be detected and treated before they cause lasting damage.