1) Hydroxychloroquine — retinal toxicity that sneaks up

Why it hurts: Hydroxychloroquine (Plaquenil) concentrates in the retina and, over months to years, can damage photoreceptors and the retinal pigment epithelium — especially the macula. Risk increases with high daily dose (relative to body weight), long cumulative exposure (≥5–10 years), kidney disease, and concurrent retinal disease. Early toxicity is often asymptomatic.

What you might notice: Blurred central vision, difficulty reading, or a subtle area of missing vision (a paracentral scotoma), but often nothing until the disease is advanced. Monitoring and prevention: Ophthalmology societies recommend a baseline eye exam within the first year of starting hydroxychloroquine and then regular screening (annual after 5 years, earlier if higher risk). Tests typically include automated visual fields and OCT imaging to detect early structural and functional changes. Reducing dose to recommended limits and following screening guidance markedly reduces risk. If detected early and the drug is stopped, progression may halt — but damage already done is usually permanent.

Action steps: If you take hydroxychloroquine, ask your prescriber about the mg/kg dosing guideline and arrange baseline and follow-up retinal screening with an eye care professional.

2) Ethambutol — optic neuropathy that steals color and central sight

Why it hurts: Ethambutol (used for TB) can cause toxic optic neuropathy by damaging the optic nerve fibers, typically producing bilateral, symmetric loss of central vision and dyschromatopsia (color vision changes). The risk is dose- and duration-related but can occur unpredictably. What you might notice: Blurry or foggy central vision, difficulty distinguishing colors (especially reds and greens), or a central blind spot. Symptoms can appear weeks to months after starting therapy. Monitoring and prevention: Regular checks of visual acuity and color vision during treatment are essential. If ethambutol-related toxicity is suspected, immediate discontinuation of the drug is recommended and urgent ophthalmology evaluation arranged — earlier cessation improves chances of partial or full recovery, though some patients have persistent deficits.

Action steps: Tell your TB team or prescribing clinician immediately if you notice color changes, central blurring, or any new vision problem. Never self-restart the drug without medical advice.

3) Topiramate — sudden myopia and angle-closure glaucoma

Why it hurts: Topiramate (Topamax) can cause a rapid forward shift of the lens-iris diaphragm from ciliochoroidal effusion, producing an acute myopic shift and secondary angle-closure glaucoma. This is not classic pupillary block glaucoma — it’s a drug-induced forward displacement leading to shallow anterior chambers and high eye pressure. What you might notice: Sudden blurry vision, halos around lights, eye pain, redness, headache, nausea — often within days to weeks of starting or increasing the dose. Because this can raise eye pressure quickly, it’s an ophthalmic emergency. Monitoring and prevention: There’s no reliable screening exam to predict who will react. The key is awareness: new visual symptoms after starting or changing topiramate dose require immediate eye care. Stopping topiramate and prompt ophthalmic treatment (pressure lowering and relieving the effusion) usually reverses the problem if done quickly.

Action steps: If you develop sudden blurred vision, pain, or halos on topiramate, stop the drug only under medical direction and get urgent ophthalmology assessment.

4) Amiodarone — corneal deposits and rare optic nerve injury

Why it hurts: Amiodarone commonly causes corneal verticillata (vortex keratopathy) — whorl-like corneal epithelial deposits seen on slit lamp exam. These deposits are very common and usually benign, causing glare or halos in some patients. More rarely, amiodarone has been linked to optic neuropathy and other posterior segment effects that can threaten vision. What you might notice: Many patients have no symptoms; others report halos, glare, or mild blurring. Sudden vision loss (rare) or progressive optic nerve changes require urgent evaluation. Monitoring and prevention: Baseline ophthalmic assessment and follow-up if symptoms occur is the practical approach. Because amiodarone is often used for serious heart conditions, decisions about stopping the drug require close coordination between cardiology and ophthalmology.

Action steps: If you notice new glare, halos, or color/central vision changes while on amiodarone, report them to your doctor and ask for an ophthalmology check.

Practical tips for anyone taking eye-risky medications

Know the red flags: sudden blurred vision, halos, new floaters, loss of color vision, a blind spot, or persistent visual distortion. These require prompt attention.

Baseline exam: get a baseline eye exam before or soon after starting drugs known to have ocular risks (hydroxychloroquine, ethambutol, amiodarone). For hydroxychloroquine, follow specialty society screening schedules. Communicate with prescribers: dosing, kidney function, and drug interactions can affect ocular risk. Don’t stop prescribed medications without discussing alternatives and risks with the prescriber.

Keep records: note start dates and doses of medications, and any eye symptoms — this helps clinicians assess causality quickly.