Drug-Induced Retinopathy

How medicines damage the retina

The retina has high blood flow and active pigment cells, which can concentrate some drugs over time. Damage happens in a few main ways:

• Pigment cell toxicity: the drug builds up in the retinal pigment epithelium, the support layer behind the photoreceptors, and the cells die (hydroxychloroquine, thioridazine, pentosan polysulfate).
• Fluid leakage: the drug disrupts barriers and fluid collects in the macula, the center of the retina (macular edema).
• Blood vessel damage: small vessels close, causing cotton-wool spots and bleeding (interferon retinopathy).
• Crystal deposits: refractile crystals settle in the retina (tamoxifen, canthaxanthin).
• Functional changes: temporary color or light changes without lasting damage (sildenafil, digoxin).

Medicines that can cause retinopathy

Ethambutol, used for tuberculosis, affects the optic nerve rather than the retina, but is screened in a similar way.

Hydroxychloroquine retinopathy

Hydroxychloroquine is a very safe and effective drug for lupus and rheumatoid arthritis, which is why many people take it for decades. The retinal risk depends mostly on dose and duration:

• risk is low (under 2%) in the first 10 years at a daily dose of 5 mg/kg of actual body weight or less
• risk rises after 5 years and climbs much higher after 20 years
• higher risk with doses above 5 mg/kg/day, kidney disease, tamoxifen use, and existing retinal or macular disease

Damage starts as a ring around the center of vision. People of Asian descent often show damage further out, so screening tests are adjusted. Once damage appears, it can keep progressing for a time even after the drug stops. More detail is on the hydroxychloroquine retinopathy page.

Screening schedule

• Baseline exam within the first year of starting, to rule out existing disease.
• Annual screening from 5 years of use onward, or sooner if you have risk factors.
• Tests: automated visual fields (10-2, plus 24-2 or 30-2 in Asian patients) and spectral-domain OCT, with fundus autofluorescence or multifocal ERG when results are unclear.

Symptoms

Early drug-related retinopathy is usually silent. That is the point of screening: by the time you notice symptoms, damage is often advanced. When symptoms do occur, they include:

• missing letters or words when reading
• small blind spots near the center of vision
• blurred or distorted vision, with straight lines looking wavy
• trouble seeing at night or adapting to darkness
• reduced color vision or glare

Diagnosis

An eye doctor (ophthalmologist or optometrist) will ask about every medicine you take, the dose and for how long, along with kidney function and weight. Tests include:

1. Dilated retinal examination
2. Optical coherence tomography (OCT): cross-section images that show thinning of retinal layers or fluid
3. Automated visual field test: maps small blind spots
4. Fundus autofluorescence: highlights stressed pigment cells
5. Multifocal electroretinogram (mfERG): measures the retina's electrical response
6. Fluorescein angiography for leaking vessels or macular edema

Treatment

There is no medicine that repairs toxic retinal damage. Management is:

• Stopping or reducing the drug, decided together with the prescribing doctor. Never stop a medicine like hydroxychloroquine on your own, because lupus flares can be serious.
• Treating macular edema with anti-inflammatory eye drops or injections when the cause is fluid.
• Low-vision aids such as magnifiers and good lighting if vision loss is permanent.

Fluid-related effects from cancer drugs and fingolimod often improve after the drug is stopped or paused. Pigment cell damage from hydroxychloroquine, thioridazine or pentosan usually does not reverse.

Frequently asked questions

Which medicines can damage the retina?

The most common is hydroxychloroquine. Others include chloroquine, thioridazine, pentosan polysulfate, high-dose tamoxifen, interferon, fingolimod, vigabatrin and several targeted cancer drugs. Most only cause problems at high doses or after long use, and screening is available for the higher-risk ones.

How often do I need an eye exam on hydroxychloroquine?

Have a baseline exam within the first year, then yearly screening after 5 years of use. If you have kidney disease, take more than 5 mg/kg/day, take tamoxifen or already have macular disease, your eye doctor may start yearly checks sooner.

Is drug-induced retinopathy reversible?

It depends on the drug. Fluid and swelling from drugs such as MEK inhibitors or fingolimod often improve after stopping. Damage to the pigment cells from hydroxychloroquine and similar drugs is usually permanent and may progress slightly after stopping, which is why early detection matters.

What does bull's-eye maculopathy mean?

It describes a ring of damaged retina around a spared center, which looks like a target on eye photos. It is the classic late sign of chloroquine or hydroxychloroquine toxicity. Modern screening aims to find damage well before this stage.

Should I stop my medicine if I am worried about my eyes?

No. Talk to your prescribing doctor and eye doctor first. For many drugs the risk to the retina is small, and stopping suddenly can cause serious flares of the condition being treated. If retinopathy is found, your doctors will plan a safe alternative.