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Hereditary, nutritional and toxic optic neuropathies
Hereditary and toxic optic neuropathies usually affect both eyes, with central visual loss, a central or centrocaecal scotoma and impaired colour vision, because they damage the papillomacular bundle fibres that are sensitive to energy shortage; before blaming a drug or a gene, compression is excluded with MRI.
Why it matters in the exam
Leber hereditary optic neuropathy (LHON): a mitochondrial disease with maternal inheritance — all children of a carrier mother inherit the mutation, but only some become ill. A young man loses central vision in one eye without pain, and the fellow eye is affected weeks to months later. In the acute fundus: a "swollen" disc with dilated small vessels, without leakage on angiography (pseudo-oedema). The commonest mutation is 11778 (in the ND4 gene), followed by 3460 and 14484 — the last with the best prognosis. Idebenone is approved in Europe. Avoiding smoking and alcohol is advised.
Dominant optic atrophy (OPA1) — the commonest hereditary optic neuropathy: slow bilateral loss from childhood, temporal disc pallor and blue-yellow colour defect. Wolfram syndrome combines type 1 diabetes, optic atrophy, diabetes insipidus and deafness. Nutritional optic neuropathy — deficiency of B12, folate, thiamine or copper, sometimes with heavy smoking and alcohol — is treated with supplements, and B12 deficiency with nerve involvement should also be checked.
Drugs: ethambutol — the commonest in exams: dose- and duration-dependent, usually appearing after months, with red-green colour loss and a central scotoma; eye examination at the start of treatment and regular follow-up, and on any complaint — stop at once; the risk is higher in renal failure. Amiodarone — slow bilateral disc swelling that lasts months. Linezolid — in prolonged treatment. Isoniazid and methanol (acute poisoning with acidosis) also damage the nerve. With an RAPD and asymmetric damage, think of a local cause.
Key points
- Bilateral damage to the papillomacular bundle: central scotoma and colours.
- LHON: mitochondrial, maternal, 11778; idebenone.
- OPA1: the commonest, childhood, blue-yellow.
- Ethambutol: red-green; stop at once.
- Exclude compression before any other diagnosis.
Summary table
| Disease | Mechanism | Sign | Treatment |
|---|---|---|---|
| LHON | Mitochondrial, 11778 | Young man, one eye then the other | Idebenone, avoid smoking and alcohol |
| Dominant optic atrophy | OPA1, dominant | Childhood, temporal pallor, blue-yellow | Follow-up and support |
| Ethambutol | Dose-dependent toxicity | Red-green, central scotoma | Stop at once |
| Amiodarone | Toxicity | Slow bilateral swelling | Consider stopping with the cardiologist |
| Nutritional | Deficiency of B12, folate, thiamine, copper | Centrocaecal scotoma | Supplements and stopping alcohol |
A free exam question
ילדים ופזילה הצורה החמורה ביותר של פגיעה תורשתית בעצבי הראיה מבחינת גיל ההופעה והירידה בראיה מתרחשת במקרים של : (the question as examined, in Hebrew)
- א. Recessive optic atrophy
- ב. Dominant optic atrophy
- ג. Leber optic neuropathy
- ד. Ataxia telangiectasia
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Sources
- International consensus statement on the clinical and therapeutic management of Leber hereditary optic neuropathy, 2017 — Diagnosis and idebenone
- WHO Consolidated Guidelines on Tuberculosis, Module 4: Treatment, 2022 — Adverse drug reactions — ethambutol
- AAO Basic and Clinical Science Course, Section 5: Neuro-Ophthalmology, 2024-2025 — Hereditary, nutritional and toxic optic neuropathies
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.