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Ocular toxicity of systemic drugs
Many drugs damage the eye, but the exam focuses on a few identifying patterns — hydroxychloroquine in the retina, ethambutol in the optic nerve, amiodarone in the cornea, steroids in the lens and pressure, topiramate in the angle and tamsulosin in the iris — and the rule is to know what to screen, when, and what to do when a finding appears.
Why it matters in the exam
Hydroxychloroquine — the most important topic: risk depends on the daily dose and duration. The recommendation: up to 5 mg/kg a day by real body weight. A baseline examination in the first year, and annual screening after 5 years — or earlier when there are risk factors: kidney disease, tamoxifen, high dose and macular disease. Tests: OCT and automated 10-2 visual field (and in people of Asian ancestry also 24-2, because the damage there is more peripheral). A "bull's eye" is a late finding; the aim is to find damage before it is visible in the fundus. When found — stop in coordination with the rheumatologist, and the damage is irreversible.
Amiodarone — whorl-like deposits in the corneal epithelium (vortex keratopathy) in almost all patients, without visual loss and without the need to stop; rarely bilateral optic neuropathy. The same corneal pattern appears in Fabry disease. Ethambutol — optic neuropathy with red-green colour loss. Steroids — posterior subcapsular cataract, raised pressure and CSC. Topiramate — bilateral angle closure and sudden myopia. Tamsulosin — IFIS in cataract surgery. Digoxin — yellow vision (xanthopsia). Sildenafil — a bluish tint to vision. Vigabatrin — irreversible concentric narrowing of the visual field, so fields are monitored.
More patterns: tamoxifen — crystalline retinal deposits and macular oedema; thioridazine — pigmentary retinopathy; isotretinoin — dry eye and night blindness; pentosan polysulfate — pigmentary maculopathy; rifabutin — uveitis with hypopyon; MEK inhibitors — subretinal fluid; immune checkpoint inhibitors — uveitis; bisphosphonates — uveitis and scleritis. In most cases the decision to stop is shared by the ophthalmologist and the prescriber.
Key points
- Hydroxychloroquine: up to 5 mg/kg; annual screening after 5 years.
- OCT and 10-2 field; 24-2 too in Asian ancestry.
- Amiodarone: benign vortex keratopathy.
- Ethambutol: red-green; topiramate: angle closure.
- Steroids: cataract, pressure, CSC.
Summary table
| Drug | Eye structure | Finding | What to do |
|---|---|---|---|
| Hydroxychloroquine | Retina | Parafoveal damage, late bull's eye | Up to 5 mg/kg; annual screening after 5 years |
| Amiodarone | Cornea, nerve | Vortex keratopathy; rarely neuropathy | Cornea — follow-up only |
| Ethambutol | Optic nerve | Red-green, central scotoma | Stop at once |
| Steroids | Lens, meshwork, choroid | PSC cataract, high pressure, CSC | Measure pressure, lowest dose |
| Topiramate | Ciliary body | Bilateral angle closure | Stop, cycloplegia |
| Vigabatrin | Retina | Irreversible field constriction | Periodic visual fields |
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Sources
- AAO Recommendations on Screening for Chloroquine and Hydroxychloroquine Retinopathy, 2016 — Dose, risk factors and screening tests
- Royal College of Ophthalmologists: Hydroxychloroquine and Chloroquine Retinopathy — Recommendations on Monitoring, 2020 — Screening schedule
- AAO Basic and Clinical Science Course, Section 12: Retina and Vitreous, 2024-2025 — Drug toxicities of the retina
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.