Makindo Medical Notes

👁️ Non-Arteritic Anterior Ischaemic Optic Neuropathy (NAION) is the most common acute optic neuropathy in older adults. It results from hypoperfusion of the optic nerve head (via the short posterior ciliary arteries), typically in patients with vascular risk factors. It must be clinically distinguished from arteritic AION (usually due to giant cell arteritis), which requires urgent steroids to prevent bilateral blindness.

📖 About

• Optic nerve ischaemia secondary to vascular compromise of the short posterior ciliary arteries.
• Occurs mostly in middle-aged or older patients with vasculopathy.
• Important to differentiate from arteritic AION (GCA) – NAION is ischaemic but non-inflammatory.

🧬 Aetiology & Risk Factors

• Hypertension, diabetes mellitus, smoking, hyperlipidaemia, obesity, obstructive sleep apnoea.
• Age > 50 years.
• "Disc at risk": small crowded optic disc with minimal cupping predisposes to ischaemia.
• Often occurs on waking → relative nocturnal hypotension reduces perfusion.
• Drug associations: PDE-5 inhibitors (e.g. sildenafil).

🩺 Clinical Features

• Sudden, painless, monocular vision loss – often noted on waking.
• Visual acuity ↓ (light perception usually preserved).
• Visual field defects: altitudinal (classically inferior field loss).
• Relative afferent pupillary defect (RAPD) in affected eye.
• Fundoscopy: swollen, pale optic disc ± peripapillary haemorrhages; contralateral "disc at risk".
• ⚠️ No systemic symptoms (e.g. headache, scalp tenderness, jaw claudication) → consider arteritic AION if present.

🔎 Investigations

• Exclude GCA urgently: FBC, ESR, CRP (arteritic AION is a medical emergency).
• OCT / fundus photography: disc swelling.
• Visual field testing: characteristic defects (often altitudinal).
• Neuroimaging usually not required unless atypical features.
• Unlike CRAO, stroke work-up not routinely indicated (NAION is hypoperfusion, not embolic).

💊 Management

• No proven acute treatment exists for NAION.
• Key priority: exclude arteritic AION → if suspected, give high-dose steroids immediately.
• Address vascular risk factors:
  • Stop smoking.
  • Optimise blood pressure, diabetes, and lipids.
  • Consider discontinuing PDE-5 inhibitors.
• Some clinicians consider long-term aspirin (evidence weak, but reasonable in vascular patients).
• Visual rehabilitation: magnifiers, low-vision support services.

📊 Prognosis

• Visual prognosis is generally poor.
• ~40% may improve slightly within 6 months, but visual field defects rarely recover.
• Fellow eye risk: ~15% over 5 years.

📚 References & Further Reading

• Berry S. Non-arteritic anterior ischaemic optic neuropathy: cause, effect, and management. Eye and Brain. 2017;9:23–28.
• Case-Based Neuro-ophthalmology – NAION
• Hayreh SS. Ischaemic optic neuropathies — where are we now? Graefes Arch Clin Exp Ophthalmol. 2013;251:1873–84.