Interferon Retinopathy

What causes interferon retinopathy

Interferons are proteins the immune system makes to fight viruses and tumors. Manufactured interferon-alpha (including peginterferon) has been used to treat hepatitis C, hepatitis B, some leukemias and myeloproliferative disorders, melanoma, and other cancers. Interferon-beta is used for multiple sclerosis, but retinopathy is much rarer with it.

Interferon is thought to damage the retina by:

• triggering immune complex deposits in small retinal blood vessels
• causing white cells to stick to vessel walls
• reducing blood flow in the tiny capillaries

The result is small areas of retinal ischemia (lack of oxygen), which appear as cotton-wool spots, the same lesions seen in diabetic retinopathy and hypertensive retinopathy.

How common is it?

Studies in people treated for hepatitis C with interferon found retinal changes in a significant proportion, ranging widely from under 20% to over half in different series. Most were mild and symptom-free. Use of interferon for hepatitis C has dropped sharply since direct-acting antiviral pills replaced it, so the condition is now less common, but it still occurs in other uses.

Risk factors

• diabetes
• high blood pressure
• higher doses and longer treatment
• combination with ribavirin
• older age

Signs and symptoms

What the eye doctor sees

• cotton-wool spots: fluffy white patches of swollen nerve fibers, usually around the optic disc
• retinal hemorrhages: small flame-shaped or dot bleeds
• microaneurysms

What the patient notices

Most people notice nothing. Less often:

• blurred vision
• spots or shadows in the vision
• reduced color vision

Severe complications (rare)

• retinal vein occlusion or retinal artery occlusion
• macular edema (swelling of the central retina)
• optic nerve damage (anterior ischemic optic neuropathy)
• neovascular glaucoma

Diagnosis

A dilated eye exam by an ophthalmologist or optometrist shows the typical changes. Additional tests may include:

• retinal photographs to document and track changes
• optical coherence tomography (OCT) to check for macular swelling
• fluorescein angiography to look at blood flow and blocked vessels

The eye doctor considers other causes of similar changes, including diabetes, high blood pressure, HIV and anemia.

Screening and monitoring

Recommendations vary, but a common approach is:

• a baseline dilated eye exam before starting interferon, especially for people with diabetes or high blood pressure
• follow-up eye exams during treatment for high-risk patients, often every few months
• prompt examination for anyone who develops visual symptoms

Treatment

• No visual symptoms and mild changes: interferon can usually continue with monitoring. Cotton-wool spots and hemorrhages usually fade within weeks to months, even if treatment continues.
• Visual symptoms or vision-threatening changes: the prescribing doctor and eye specialist decide together whether to reduce or stop interferon.
• Complications such as macular edema or new blood vessel growth are treated with standard eye treatments, such as injections into the eye or laser.
• Control blood pressure and blood sugar to reduce risk.

Outlook

Most interferon retinopathy is mild, symptom-free and reversible. Permanent vision loss is rare and mainly follows retinal vessel occlusion or optic nerve damage. Early detection in high-risk patients makes serious outcomes even less likely.

Frequently asked questions

What is interferon retinopathy?

It is a side effect of interferon treatment that causes small areas of poor blood flow in the retina. Eye doctors see cotton-wool spots and small hemorrhages. It is usually mild, causes no symptoms and fades on its own, but rarely can affect vision.

Does interferon retinopathy cause vision loss?

Usually not. Most people have no symptoms. Rarely, blocked retinal blood vessels, macular swelling or optic nerve damage can cause vision loss. Report any new blurring, blind spots or sudden vision changes during treatment promptly.

Who needs eye exams on interferon?

People with diabetes or high blood pressure are at higher risk and should have a baseline dilated eye exam before starting interferon and regular checks during treatment. Anyone with new vision symptoms should be examined promptly.

Does interferon retinopathy go away?

In most people, yes. Cotton-wool spots and small hemorrhages usually resolve within weeks to months, often while treatment continues and almost always after it stops. Severe complications may leave permanent damage.

Do I need to stop interferon if I have retinopathy?

Not usually for mild, symptom-free changes. If vision is affected or there are serious changes such as blocked vessels, your doctors may reduce or stop interferon. Do not stop treatment without discussing it with your prescribing doctor.