Medications That Affect the Eyes: Side Effects You Should Know

When we think about the side effects of a medicine, we usually think about the stomach, the liver or drowsiness. Yet the eye is one of the most sensitive organs to medication effects. Its tiny blood vessels, transparent tissues, delicate tear film and highly active retina can all be affected by drugs taken for completely unrelated conditions, from arthritis and acne to epilepsy, heart rhythm problems and an enlarged prostate.

Most medication-related eye effects are mild and reversible, such as dry eyes from antihistamines. A few are serious and can cause permanent vision loss if not detected early. The good news is that, for most of these, there are clear screening recommendations or warning signs. This guide covers the key medicines, what they can do, and how to stay safe. It is not a reason to stop any medicine: always discuss concerns with the doctor who prescribed it.

Why medicines affect the eyes

Medicines reach the eye through the bloodstream and, in some cases, through tears. The retina has one of the highest metabolic rates in the body and contains pigment that can bind certain drugs. The lens can be affected by long-term exposure. The iris and ciliary body contain receptors that respond to drugs targeting the nervous system, which can change pupil size or the drainage angle of the eye. The tear-producing glands are sensitive to drugs that dry other mucous membranes. These mechanisms explain why such a wide variety of medicines can produce eye effects.

Overview of key medications

Corticosteroids: glaucoma and cataract

Steroids are among the most useful medicines in modern medicine, but they are also the most important group of drugs affecting the eyes. They can be given as eye drops, tablets, injections, inhalers, nasal sprays and skin creams, and all routes can affect the eye, though eye drops and injections near the eye carry the highest risk.

Steroid-induced raised eye pressure and glaucoma

In a proportion of people, called steroid responders, steroids reduce the outflow of fluid from the eye and pressure rises. This typically develops over weeks of use. Without monitoring, the high pressure can damage the optic nerve and cause glaucoma, often without symptoms. People with existing glaucoma, a family history of glaucoma, high myopia or diabetes are at greater risk. The pressure usually returns to normal after the steroid is stopped, but nerve damage that has already occurred is permanent.

Steroid-induced cataract

Long-term steroid use can cause a particular type of cataract at the back of the lens (posterior subcapsular cataract). It tends to cause glare and difficulty reading, and can develop at a younger age than typical age-related cataract. It does not reverse when steroids are stopped, but it can be treated with cataract surgery.

Other steroid effects

Steroids can also trigger central serous chorioretinopathy, a build-up of fluid under the retina, and they can worsen eye infections, especially herpes simplex and fungal infections. That is why steroid eye drops must only be used under an eye doctor's supervision. See our guide to eye drops and their correct use.

Hydroxychloroquine: retinal screening is essential

Hydroxychloroquine is widely used for lupus, rheumatoid arthritis and other autoimmune conditions. It is generally well tolerated and very valuable, but after years of use it can damage the retina (hydroxychloroquine retinopathy). Early damage causes no symptoms. Once advanced, it can affect central vision and may continue to progress even after the drug is stopped.

The main risk factors are the daily dose relative to body weight, the duration of use (risk rises significantly after five years), kidney disease and the use of tamoxifen. The prescribing doctor sets the dose; you should never adjust it yourself.

Screening recommendations

• A baseline eye examination early in treatment, to document the retina and identify pre-existing disease.
• Annual screening after five years of use, according to the American Academy of Ophthalmology, or earlier in people with additional risk factors. The UK Royal College of Ophthalmologists recommends annual monitoring after five years of use, or after one year for those with additional risk factors.
• Screening uses sensitive tests such as optical coherence tomography (OCT), automated visual field testing and fundus autofluorescence. A simple reading test is not enough.

Chloroquine, a related drug, carries a higher risk and requires similar or closer monitoring.

Tamsulosin and intraoperative floppy iris syndrome

Tamsulosin and other alpha-1 blockers (such as alfuzosin, doxazosin and silodosin) are used mainly for urinary symptoms caused by an enlarged prostate, and sometimes for kidney stones. They relax the muscle of the iris that holds the pupil wide. This causes no problems in daily life, but during cataract surgery the iris may become floppy, billow and constrict, a phenomenon called intraoperative floppy iris syndrome (IFIS).

Surgeons can manage IFIS very effectively with specific techniques and medicines, provided they know about it in advance. The effect can persist even after the drug has been stopped, sometimes for years.

• Tell your eye surgeon if you take or have ever taken tamsulosin or similar drugs.
• Stopping the medicine before surgery is generally not necessary and may not prevent IFIS; follow your surgeon's advice.
• If you are about to start tamsulosin and already know you have a cataract, it is worth mentioning this to your doctor.

Antihistamines and other drying medicines

Many medicines reduce tear production and cause or worsen dry eye. Common examples include oral antihistamines for allergy and sleep, decongestants, some antidepressants and anti-anxiety medicines, bladder medicines with anticholinergic effects, diuretics, beta-blockers and hormone treatments.

• Symptoms include grittiness, burning, fluctuating vision and contact lens discomfort.
• Preservative-free lubricating drops usually help.
• For allergic eye symptoms, antihistamine eye drops may cause less general dryness than tablets, though both can be used together under advice.

Some drugs with anticholinergic or adrenergic effects, including certain antihistamines, decongestants, antidepressants and anti-nausea drugs, widen the pupil. In people with naturally narrow drainage angles, often those who are long-sighted, this can rarely trigger acute angle-closure glaucoma. Leaflets often warn against use in glaucoma; this mainly applies to the narrow-angle type, so ask your eye doctor which type you have.

Isotretinoin

Isotretinoin, used for severe acne, reduces the activity of oil glands throughout the body, including the meibomian glands of the eyelids. Common eye effects include:

• Dry eye and blepharitis, sometimes making contact lenses uncomfortable.
• Conjunctivitis and irritation.
• Reduced night vision, which is uncommon but reported; take care with night driving and report any change.

Most effects improve after treatment ends, though dry eye may persist in some people. Lubricants, warm compresses and lid hygiene usually help. If you are considering laser refractive surgery, surgeons typically recommend waiting several months after stopping isotretinoin.

Topiramate: angle closure and sudden myopia

Topiramate is used for epilepsy, migraine prevention and, in combination with other drugs, weight management. A rare but important side effect is a swelling of the ciliary body that pushes the lens and iris forward. This can cause a sudden shift towards short-sightedness and, more seriously, acute angle-closure glaucoma in both eyes at once.

• It usually happens within the first few weeks of starting the drug or increasing the dose.
• Symptoms include sudden blurred distance vision, eye pain, redness, headache, nausea and halos.
• Unlike typical angle-closure glaucoma, it is not caused by pupil dilation, so standard laser treatment is not the solution.
• Treatment involves stopping the drug under medical supervision and pressure-lowering treatment.

Amiodarone

Amiodarone treats serious heart rhythm problems. Almost everyone who takes it for a period develops fine deposits in the cornea, known as vortex keratopathy, which form a whorl-like pattern. These usually do not affect vision significantly, though some people notice halos around lights or glare. They fade after the drug is stopped.

Much less commonly, amiodarone has been associated with optic neuropathy, which can cause gradual or sudden vision loss and swelling of the optic nerve, sometimes in both eyes. Any reduction in vision should be reported to your doctor promptly. Amiodarone is often essential for heart health, so decisions about stopping or switching are made carefully between your cardiologist and eye doctor.

Other medicines worth knowing about

• Ethambutol (tuberculosis): can damage the optic nerve; vision and colour testing is recommended during treatment.
• Sildenafil and related drugs (erectile dysfunction): can cause temporary blue tinge and light sensitivity; rarely linked to optic nerve problems.
• Tamoxifen (breast cancer): rarely causes retinal crystals or cataract.
• Bisphosphonates (osteoporosis): rarely cause inflammation of the eye, such as uveitis or scleritis.
• Some cancer therapies and biologics: can cause a range of eye effects; your oncology team will advise on monitoring.
• Semaglutide and related GLP-1 drugs: rapid blood sugar improvement can temporarily worsen diabetic retinopathy, and a possible association with a type of optic nerve stroke is being investigated; people with diabetic retinopathy should keep up with retinal screening.

How to protect your eyes when taking medicines

1. Keep a full medication list, including over-the-counter drugs, supplements, inhalers and creams, and bring it to every eye appointment.
2. Tell your eye doctor about medicines you have taken in the past, particularly tamsulosin, steroids and hydroxychloroquine.
3. Tell prescribers about your eyes, especially glaucoma, narrow angles or previous central serous chorioretinopathy.
4. Attend recommended screening, such as eye pressure checks with steroids or retinal scans with hydroxychloroquine.
5. Read leaflets and ask your pharmacist about eye-related warnings.
6. Never stop or change a dose without talking to the prescribing doctor.

When to see a doctor

Mild dryness or slight blurring that appears with a new medicine is worth mentioning at your next appointment. Some symptoms, however, need urgent attention.