Chorioretinitis

What happens in chorioretinitis

The choroid is a layer of blood vessels that nourishes the outer retina. The retina is the light-sensing layer that sends images to the brain. Infections or immune reactions can inflame both layers at once. The inflamed patch swells, white blood cells spill into the gel of the eye (the vitreous) and cause floaters and haze, and the damaged retina in that spot stops working.

When the inflammation settles it leaves a scar, a pale patch edged with dark pigment. A scar in the edge of the retina may cause only a small blind spot you never notice. A scar in the macula, the center of vision used for reading and faces, can cause permanent loss of central vision.

Doctors sometimes use retinochoroiditis when the retina is mainly inflamed (as in toxoplasmosis), and chorioretinitis when the choroid is the main site. In practice the terms overlap.

Symptoms

• floaters: dots, cobwebs or a haze drifting across vision
• blurred, foggy or patchy vision
• a blind spot or shadow
• distorted vision if the macula is affected
• eye redness, pain and light sensitivity (photophobia) when the front of the eye is also inflamed

Some patches cause no symptoms at all and are found on a routine eye exam. Babies with congenital infection may have a squint, wobbly eyes (nystagmus) or poor vision.

Causes

Infections

Non-infectious causes

Autoimmune and inflammatory conditions can cause similar inflammation, including sarcoidosis, Behçet's disease, birdshot chorioretinopathy, Vogt-Koyanagi-Harada disease and serpiginous choroiditis. Lymphoma inside the eye can mimic chorioretinitis in older adults.

Risk factors

• weakened immunity from HIV/AIDS, organ transplant, chemotherapy or long-term steroids
• eating undercooked meat, or contact with cat litter or soil
• unsafe sex (syphilis, HIV)
• travel to or living in areas where tuberculosis or toxoplasmosis is common
• being born to a mother infected during pregnancy

Diagnosis

An ophthalmologist (eye doctor) or retina specialist will:

1. Check vision and eye pressure.
2. Dilate the pupils and examine the retina with a slit lamp and ophthalmoscope. The look of the lesion often suggests the cause.
3. Photograph and scan the retina: fundus photos, optical coherence tomography (OCT) and fluorescein or indocyanine green angiography to map the inflammation.
4. Order blood tests: syphilis serology, HIV, Toxoplasma antibodies, TB tests (interferon-gamma release assay), and others depending on the picture, plus a chest X-ray or CT for TB or sarcoidosis.
5. Sometimes take a small sample of fluid from inside the eye (aqueous or vitreous tap) for PCR testing to identify viruses, Toxoplasma or fungi.

Treatment

Treatment depends on the cause and on how close the inflammation is to the macula and optic nerve.

• Toxoplasmosis: small patches far from the center may be watched in healthy adults, as many settle on their own in 6 to 8 weeks. Patches threatening central vision are treated with antiparasitic antibiotics, often with oral steroids started after the antibiotics to reduce scarring. Preventive antibiotics can reduce recurrences in people with frequent flare-ups.
• CMV retinitis: antiviral drugs given by mouth, by IV, or injected into the eye, plus restoring immunity (for example antiretroviral therapy in HIV).
• Syphilis: treated like neurosyphilis with IV penicillin.
• Tuberculosis: a full course of TB drugs, with steroids under specialist supervision.
• Herpes viruses (acute retinal necrosis): urgent high-dose antivirals, sometimes injections into the eye, and laser to prevent detachment.
• Fungal infection: antifungal medicines and sometimes vitrectomy surgery.
• Non-infectious causes: steroids (drops, injections, tablets) and immune-suppressing or biologic medicines.

Steroids alone must never be used before an infection is excluded, because they can make infectious chorioretinitis much worse.

Complications and outlook

Possible complications include permanent scars and blind spots, macular damage, retinal detachment, cataract, glaucoma, swelling of the macula, and abnormal new blood vessels under the retina (choroidal neovascularization) that can bleed years later.

The outlook depends on the location. Many people with a small patch away from the macula keep good vision. Toxoplasmosis can flare again from the edge of old scars, so anyone with a known scar should seek an eye check promptly if new floaters or blur develop. People with HIV and a low CD4 count need regular eye screening.

Prevention

• Cook meat thoroughly, wash fruit and vegetables, and wash hands after gardening.
• Pregnant people should avoid changing cat litter and eating undercooked or cured meat.
• Use condoms and get tested for syphilis and HIV.
• Take antiretroviral therapy as prescribed to keep immunity strong.

Frequently asked questions

What is chorioretinitis?

Chorioretinitis is inflammation of the choroid and retina at the back of the eye. It is a type of posterior uveitis. It is most often caused by infections such as toxoplasmosis, CMV or syphilis, and can cause floaters, blurred vision and permanent blind spots if the center of the retina is affected.

What is the most common cause of chorioretinitis?

Toxoplasmosis, a parasite infection caught from undercooked meat, cat feces or before birth, is the most common cause worldwide. In people with weakened immunity, CMV is an important cause. Syphilis and tuberculosis must always be considered, because both are treatable.

Can chorioretinitis be cured?

The active infection or inflammation can usually be controlled with the right treatment. However, the scar left behind is permanent, and vision lost in that area does not come back. Toxoplasma can also reactivate later, so recurrences are possible.

Is chorioretinitis contagious?

The eye inflammation itself is not contagious. Some of the underlying infections can spread, such as syphilis through sex, tuberculosis through the air, and CMV through body fluids. Toxoplasmosis does not spread from person to person, except from a pregnant mother to her baby.

How long does chorioretinitis last?

An active episode of toxoplasma chorioretinitis usually settles over 4 to 8 weeks, with or without treatment. Viral and autoimmune causes may need months of treatment. Some forms, such as birdshot chorioretinopathy, are long-term and need ongoing monitoring.