Birdshot chorioretinopathy
Birdshot chorioretinopathy (BSCR) is a rare autoimmune disease affecting the back of the eye. Early symptoms include blurred vision and seeing floaters.
The condition goes by several names, including birdshot uveitis because it affects the uvea, the inner lining at the back of the eye. You might also see it called birdshot retinochoroidopathy, birdshot retinochoroiditis, birdshot retinopathy or simply birdshot.
There's no cure, but treatments can reduce inflammation in the eye and help prevent flare-ups. Later symptoms can include vision loss, so if you're diagnosed with birdshot chorioretinopathy, you'll have regular follow-up appointments with an ophthalmologist. You'll also get support to help you adjust and make the most of your vision.
Birdshot chorioretinopathy symptoms
Birdshot chorioretinopathy typically affects both eyes. Many different eye conditions share the same early symptoms as birdshot chorioretinopathy, making getting a diagnosis difficult. Your optician or ophthalmologist may need to rule out other more common conditions first.
Symptoms in the early stages tend to be mild and include:
- Seeing floaters in your vision (dark spots that pass across your vision)
- Blurred vision that gradually gets worse
As time goes on, other symptoms can develop, including:
- Difficulty seeing at night (night blindness)
- Seeing flashes of light
- Becoming more sensitive to light (photophobia)
- Trouble with glare
- Reduced colour vision, including difficulty with contrast sensitivity
- Distorted vision
- Loss of depth perception and/or peripheral vision
Birdshot chorioretinopathy gets its name from the yellow or white colour lesions (spots) that appear on the fundus in the retina at the back of the eye. These retinal spots show up in a scattered pattern resembling birdshot.
Birdshot chorioretinopathy is a type of posterior uveitis (posterior because it affects the back of the eye). It is more likely to lead to vision loss than other types, such as anterior uveitis. Untreated, it can lead to progressive loss of visual acuity, meaning you see less clearly.
Complications can also develop that have the potential to affect your vision. Most commonly, macular oedema, in which leakage from the affected blood vessels causes swelling in the macula. This swelling can affect your central vision and lead to vision loss.
Another potential complication is the growth of new abnormal blood vessels (subretinal choroidal neovascularisation). These can leak and bleed, affecting your vision.
Symptoms vary from person to person. Some people experience mild symptoms, others more severe. Many people also have episodes of flare-ups and remissions, with fluctuating symptoms.
Birdshot chorioretinopathy treatment
You'll see an ophthalmologist (hospital eye doctor) for review and treatment, and your treatment plan will depend on your symptoms. Around 20% of people with birdshot uveitis get better without needing treatment and don't experience vision loss (Source: Orphanet Journal of Rare Diseases).
However, most people develop chronic disease and need treatment to get the condition under control and help prevent complications that can worsen vision loss. Although it can't be cured, treatments aim to control inflammation and prevent sight loss.
The first treatment is usually oral corticosteroids to reduce inflammation in the eye (intraocular inflammation). The dose may be very high initially, then reduced. Steroids can also help improve your peripheral vision if it has been affected. You may also take immunosuppressants that prevent the immune system from attacking healthy tissue, as happens with birdshot chorioretinopathy.
Both steroids and immunosuppressants have side effects which need to be carefully monitored. You may need additional medicines or supplements to manage side effects, for example, vitamin D and calcium to protect against osteoporosis. Some people may develop bone problems, kidney problems and hypertension (high blood pressure), and cataracts can also be a side effect of immunomodulatory therapy.
Your ophthalmologist will aim to use the lowest possible dose of effective medicine to limit side effects. While taking immunosuppressants, you will have follow-up monitoring appointments with your ophthalmologist. You may also see other specialists such as a rheumatologist or renal specialist to monitor the side effects of treatment.
If you develop complications, you may need additional treatment. Macular oedema can be treated with topical steroids and anti-inflammatory medicine, although an intravitreal injection may also be used. If you develop new abnormal blood vessels, you may need laser therapy.
Diagnosis of birdshot chorioretinopathy
Birdshot chorioretinopathy can be tricky to diagnose. It's rare, and many other eye conditions cause similar symptoms, so it might not be the first thing your optician or ophthalmologist suspects. The tell-tale yellow and white lesions on the retina aren't always visible in the early stages.
The tests to diagnose birdshot chorioretinopathy can include:
- Optical coherence tomography (OCT), a non-invasive technique a bit like an ultrasound, takes images of the retina.
- Visual field tests to assess your peripheral vision.
- Fluorescein angiography uses fluorescein dye to show how well the blood vessels at the back of the eye are working.
- Indocyanine green angiography uses a dye visible in infrared light to take images of the retina, choroid, and optic disc blood vessels.
- Electroretinogram test (ERG) assesses how well the electrical responses in the retina are working.
- A blood test to confirm whether you have the HLA-A29 antigen.
- Examination of the pattern of birdshot lesions to help assess whether the condition is acute or chronic. In chronic birdshot chorioretinopathy, the choroidal lesions tend to merge and look larger.
- Sometimes a biopsy may be needed to confirm the diagnosis.
When to get medical advice
The NHS advises that we get regular eye tests, at least every two years. As well as checking your vision, an optometrist will look at your overall eye health and can detect a range of eye conditions.
Living with birdshot chorioretinopathy
It's completely natural to worry if you've been diagnosed with birdshot chorioretinopathy. You'll probably need long-term follow-up with your ophthalmologist and have to deal with flare-ups of the condition, along with treatment side effects. It's also normal to worry about how you'll cope if you experience loss of visual function over time.
We're here to support you at every step of living with birdshot chorioretinopathy. We can connect you to others with similar experiences and give practical advice and support.