Examqo › Examqo library › Ophthalmology › Neuro-ophthalmology · IMLE
Ischaemic optic neuropathy (NAION and AAION)
Anterior ischaemic optic neuropathy is an infarct of the optic nerve head with sudden, painless loss of vision and disc swelling; the non-arteritic form (NAION) is linked to a crowded disc and vascular risk factors and has no proven treatment, and the arteritic form (AAION) results from giant cell arteritis and needs steroids at once to save the fellow eye.
Why it matters in the exam
NAION — a person aged 50 or over who wakes in the morning with reduced vision in one eye, an altitudinal field defect (usually inferior), an RAPD and sectoral hyperaemic disc swelling. The fellow eye shows a small crowded disc without a cup ("disc at risk"). Risk factors: hypertension, diabetes, sleep apnoea, nocturnal hypotension and certain drugs such as amiodarone. IONDT showed that optic nerve sheath decompression does not work and may harm; the fellow eye is affected in about 15% within 5 years. Risk factors are treated and nocturnal hypotension avoided.
AAION — the more important topic in the exam, because it is an emergency. An older patient (usually over 70) with new headache, scalp tenderness, jaw claudication, shoulder girdle pain (PMR), fever and weight loss, and profound loss of vision. The disc is swollen and chalky white, sometimes with cilioretinal artery occlusion. ESR and CRP are high, with thrombocytosis. Without treatment the fellow eye may be affected within days.
Treatment of AAION: with visual loss — intravenous methylprednisolone 1 g a day for 3 days, then oral prednisone 1 mg/kg a day with a slow taper; without visual loss oral treatment can be started. Temporal artery biopsy (or ultrasound) is done within 1–2 weeks of starting treatment — the steroid does not abolish the finding at once. Tocilizumab reduces steroid requirement (GiACTA). The posterior form (PION) appears mainly after long prone spinal surgery with blood loss — the disc is normal at first.
Key points
- Infarct of the optic nerve head: sudden, painless, swollen disc.
- NAION: crowded disc, altitudinal defect, no proven treatment.
- AAION: GCA, chalky white disc, high inflammatory markers.
- GCA with visual loss → methylprednisolone 1 g a day for 3 days.
- Biopsy within 1–2 weeks of starting the steroid.
Summary table
| Feature | NAION | AAION |
|---|---|---|
| Age | 50 and over | Usually over 70 |
| Associated symptoms | None; onset on waking | Headache, jaw claudication, PMR, weight loss |
| Disc | Sectoral hyperaemic swelling; disc at risk in fellow eye | Chalky white swelling |
| Laboratory | Normal | High ESR and CRP, thrombocytosis |
| Treatment | Risk factors; no proven treatment | Steroids at once; biopsy; tocilizumab |
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
The full version is open to subscribers of: Ophthalmology, Medical licensing exam (IMLE), Neurology, Internal medicine, Geriatrics.
Subscriber? Read the full topic Plans and prices 25 free questions
Sources
- EULAR recommendations for the management of large vessel vasculitis, 2018 update — Giant cell arteritis
- Ischemic Optic Neuropathy Decompression Trial (IONDT) Research Group, 1995 — Optic nerve sheath decompression in NAION
- AAO Basic and Clinical Science Course, Section 5: Neuro-Ophthalmology, 2024-2025 — The patient with decreased vision: 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.