Neuro-Ophthalmic
Non-Arteritic Ischaemic Optic Neuropathy
Also known as: NAION, non-arteritic ischaemic optic neuropathy, ischaemic optic neuropathy, ION, anterior ischaemic optic neuropathy, disc swelling vascular, altitudinal field defect, crowded disc
Filed as: Urgent
Source-cited from the record's own evidence list. Clinical content programme led by Dr Ankit Mathur, PhD, Grad Cert Ocu Thera, B.S. Optom. How the clinical content is governed
Clinical decision support only
Overview
Infarction of the anterior optic nerve head, typically noticed on waking, painless, with an altitudinal field defect and a relative afferent pupillary defect. The disc is swollen, often in one sector, and acuity ranges from near normal to severe loss. The immediate task is separating it from the arteritic form, which is treatable and threatens the fellow eye, so inflammatory markers are checked the same day in patients over 50.
Recognition
Symptoms: what patients report
- Sudden or wake-up painless loss of vision in one eye.
- Altitudinal field defect — typically inferior loss (the inferior half of vision is gone).
- Visual acuity ranges from 6/9 to no light perception.
- No pain on eye movement — this distinguishes NAION from optic neuritis.
- The patient may notice the field defect rather than acuity loss.
Signs: what the examination shows
- Swollen optic disc — typically sectoral or diffuse, often hyperaemic with peripapillary haemorrhages.
- Altitudinal visual field defect on formal testing.
- Relative afferent pupillary defect (RAPD).
- Reduced visual acuity (variable).
- Disc-at-risk anatomy in the fellow eye — small, crowded optic disc with minimal or absent cup.
- No cells or flare in the anterior segment.
What OptoGuide™ covers for non-arteritic ischaemic optic neuropathy
- Pattern reasoning: what this combination of findings points to, and its differentiators
- Don't-miss risks and escalation triggers
- Management tiers with linked Australian therapeutics
- Referral urgency, specialty, and letter drafting
Sources
- Non-Arteritic Anterior Ischemic Optic Neuropathy (NAION) — EyeWiki
- Non-Arteritic Anterior Ischemic Optic Neuropathy — NANOS
- The Neuro-Ophthalmology Survival Guide (Pane, Miller & Burdon) — standard reference text
- Clinical, Biological, and Ophthalmological Characteristics Differentiating Arteritic From Non-Arteritic Anterior Ischaemic Optic Neuropathy. Parreau S, Dentel A, Mhenni R, et al. Eye (London, England). 2023;37(10):2095-2
- Non-Arteritic Anterior Ischaemic Optic Neuropathy and Its Masquerades: A Comprehensive Diagnostic Review. Lawrence AL, Savino PJ, Danesh-Meyer HV. Clinical & Experimental Ophthalmology. 2026 May-Jun;54(4):537-553.
- NAION or Not NAION? A Literature Review of Pathogenesis and Differential Diagnosis of Anterior Ischaemic Optic Neuropathies. Martin-Gutierrez MP, Petzold A, Saihan Z. Eye (London, England). 2024;38(3):418-425.
- Utility of erythrocyte sedimentation rate and C-reactive protein for the diagnosis of giant cell arteritis. Kermani TA, Schmidt J, Crowson CS, et al. Seminars in Arthritis and Rheumatism. 2012;41(6):866-71.
- Anterior ischemic optic neuropathy due to giant cell arteritis with normal inflammatory markers. Yoeruek E, Szurman P, Tatar O, et al. Graefe’s Archive for Clinical and Experimental Ophthalmology. 2008;246(6):913-5.
Standard texts: Kanski's Clinical Ophthalmology: A Systematic Approach, Oxford Handbook of Ophthalmology, Oxford American Handbook of Ophthalmology, Signs in Ophthalmology: Causes & Differential Diagnosis.