What is birdshot chorioretinitis?
Birdshot chorioretinitis is a long‑lasting disease that causes inflammation, or swelling, in two important parts of the eye called the retina and the choroid. The retina is the thin, light‑sensitive layer at the back of your eye that helps you see, and the choroid is a layer of blood vessels behind it that brings the eye food and oxygen. In this disease, doctors can see many small, pale spots in the back of the eye that look like tiny shotgun pellets, which is why it is called “birdshot.” It almost always affects both eyes and can slowly change a person’s vision over many years if the swelling continues.
People with birdshot chorioretinitis usually notice that their vision changes slowly over time. They may see floaters, which look like tiny spots, strings, or cobwebs drifting across what they are looking at. They may also notice strange light effects called photopsias, which can look like quick flashes, flickers, sparkles, or shimmering lights, even when nothing bright is around. Because flashes and floaters can also be a sign of a retinal tear or detachment, anyone who suddenly notices these symptoms should see an eye doctor right away.
People may notice that their vision is blurry or fuzzy, making it harder to read or see small details, and straight lines can look wavy or bent. Some people have trouble seeing at night or in dim light and may bump into things or misjudge steps because their side or depth vision is not as good. Colors can look faded, washed out, and dull, and some people see a shimmery, fan‑like pattern, especially when their eyes are closed. These changes usually affect both eyes and often start so slowly that a person just feels that “something is not right” with their vision.
For many people with birdshot chorioretinitis, this is how their journey begins, and it can take several visits and sometimes more than one eye doctor before the correct diagnosis is finally made.
What causes it?
Doctors do not know the exact cause of birdshot chorioretinitis. They believe it is an autoimmune disease, which means the body’s own defense system gets confused and starts attacking healthy eye tissue by mistake. Most people with this disease have a special gene marker called HLA‑A29, which may make them more likely to get it, but having this marker does not mean a person will definitely get the disease. HLA‑A29 is found in about 7-10% of people in Western countries. Almost all people with birdshot chorioretinitis have this HLA‑A29 marker, so it is strongly linked to the disease. However, birdshot chorioretinitis itself is very rare, affecting only about one out of a million people in the general population. This means that even though the HLA‑A29 marker is common, only a very small number of people who have it will ever develop birdshot chorioretinitis. Other things, like infections or the environment, may also help trigger the problem in people who already have this gene marker.
How is it treated?
The main goal of treatment is to calm the swelling in the eyes and protect vision as much as possible. Doctors often start with strong medicines called corticosteroids, which are powerful drugs that reduce inflammation; these can be given as pills, eye drops, injections near or inside the eye, or through a vein. Because steroids can cause side effects if used at high doses for a long time, doctors usually lower the dose over time and often add other medicines called immunosuppressants to help keep the immune system from attacking the eyes. Some people with very mild disease and good vision may not need treatment right away, but they still need regular eye checkups to watch for changes.
Doctors do not use just one “best” medicine for everyone with birdshot chorioretinitis. Instead, they choose from several strong medicines that calm down the immune system and protect vision, such as cyclosporine, mycophenolate, azathioprine, or methotrexate, often along with a low dose of steroids to control eye swelling. The patient and doctor choose the medicine together. They talk about possible side effects and how each treatment fits the patient’s daily life, aiming to keep the uveitis from coming back while keeping side effects as low as possible.
If these medicines do not work well enough or cause too many side effects, some people may get newer “biologic” medicines, which are special drugs that target parts of the immune system more directly. The most commonly used medicine is adalimumab (Humira), which is the only non‑steroid drug officially approved to treat non‑infectious uveitis. Adalimumab is given as a shot under the skin, usually every two weeks, and can help some people lower their steroid dose and keep eye inflammation under better control. Because each person’s health and eyes are different, the eye specialist and patient work together to choose the medicine or mix of medicines that controls the disease while causing the fewest side effects, and it is very important to take these medicines exactly as directed and have regular blood tests and checkups to make sure they stay safe and effective.
What is the prognosis?
The outlook for birdshot chorioretinitis is not the same for everyone and depends on how severe it is and how early it is found and treated. With careful, long‑term treatment and regular visits to an eye doctor, many people can keep their vision steady, see some improvement, and in some cases go into remission, which means the disease becomes quiet for a long time with little or no active inflammation.
If the eye inflammation is not well controlled, it can lead to serious eye changes over time. These can include swelling in the center of the retina called cystoid macular edema, damage to the optic nerve, thinning and narrowing of the blood vessels in the retina, and abnormal new blood vessels under the retina, all of which can cause permanent vision loss. People can also develop cataracts or glaucoma, which may cause further vision loss even after the inflammation is treated.
Birdshot chorioretinitis lasts a long time and can flare up again, some people may still lose vision over the years, especially if the swelling is not well controlled or if treatment starts late. This is why it is very important to follow the treatment plan closely and see the eye doctor often so any new problems can be found and treated early. Birdshot chorioretinitis mainly affects the eyes and is usually described as an “eye‑only” condition, meaning there is eye inflammation but no regular pattern of serious problems in the rest of the body.
It’s important to see a uveitis specialist (Like me!) to control inflammation early and aggressively, and use advanced treatments to get better long-term results and reduce the chance of permanent vision loss from uveitis.
