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Non-Arteritic Anterior Ischemic Optic Neuropathy (NAION)

Sudden painless monocular vision loss from acute ischemia of the optic nerve head supplied by short posterior ciliary arteries; the most common acute optic neuropathy in adults > 50 with characteristic disc-at-risk anatomy and altitudinal visual field defects.

Written by: Saygı Hospital Health Guide Editorial Board
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This content has been compiled by the Saygı Hospital Health Guide Editorial Board and is periodically reviewed by a specialist physician.

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What is Non-Arteritic Anterior Ischemic Optic Neuropathy (NAION)?

NAION is acute ischemia of the laminar and prelaminar optic nerve head supplied by the short posterior ciliary arteries (paraoptic branches), producing axonal infarction with disc edema and progressive optic atrophy. Pathophysiologically, it represents a compartment syndrome in a structurally crowded optic nerve head (small disc with no cup, the disc-at-risk) compounded by hypoperfusion (nocturnal hypotension, sleep apnea, vasculopathic small-vessel disease).

Clinical presentation: sudden painless monocular vision loss noticed on awakening or first thing in the morning (because of nocturnal hypotension), altitudinal visual field defect (60 percent inferior, 20 percent superior, 20 percent central or other patterns), reduced color vision and contrast sensitivity, relative afferent pupillary defect (RAPD), and acute disc edema (sectoral or diffuse, often hyperemic) with peripapillary hemorrhages; second eye involvement occurs in 15–20 percent over 5 years (rare bilateral simultaneous presentation).

Critical differential — arteritic AION (giant cell arteritis): occurs in patients > 70, severe vision loss often counting fingers or worse, pale disc edema (chalk-white), associated headache, jaw claudication, scalp tenderness, polymyalgia rheumatica symptoms, very high ESR (often > 100) and CRP, normal disc-at-risk anatomy may not be present; emergent high-dose IV methylprednisolone (1 g/day for 3 days) prevents fellow-eye blindness and confirms with temporal artery biopsy. Workup of all AION includes immediate ESR, CRP, CBC, and same-day temporal artery palpation; biopsy if any GCA features.

Symptoms

Sudden painless monocular vision loss
Vision loss often noticed on awakening (nocturnal hypotension)
Altitudinal visual field defect (often inferior horizontal cut)
Decreased color vision (often dyschromatopsia)
Relative afferent pupillary defect (RAPD)
Disc edema (sectoral or diffuse) with peripapillary splinter hemorrhages
No eye pain (key differentiator from optic neuritis which has pain on movement)
Vision typically stable (no progression) after initial loss
Stereotypic recurrence in fellow eye possible (15–20 percent over 5 years)

Risk Factors

Age > 50 years (mean 60s)
Disc-at-risk anatomy: small crowded optic disc with no physiologic cup (cup-to-disc < 0.2)
Hypertension
Diabetes mellitus
Hyperlipidemia
Obstructive sleep apnea (very strong association)
Nocturnal hypotension (overaggressive antihypertensive at bedtime)
Sildenafil, tadalafil, vardenafil (PDE5 inhibitors — increased risk)
Smoking
Hypercoagulable states (less common)
Anemia, severe blood loss with hypotension
Cardiac surgery with prolonged hypotension (perioperative ION)

When to See a Doctor?

If you experience any of the following symptoms, seek medical attention promptly:

  • Sudden painless vision loss in one eye — emergent same-day evaluation
  • Vision loss noticed on awakening
  • Visual field cut (top half or bottom half missing)
  • Vision loss with headache, jaw pain, scalp tenderness in patient > 70 (rule out GCA — emergency)
  • Known NAION in one eye with new symptoms in fellow eye (emergency)
  • Sleep apnea symptoms (loud snoring, witnessed apneas, daytime sleepiness)
  • Newly started PDE5 inhibitor with vision changes

Treatment Methods

01
Same-day comprehensive eye exam: best-corrected visual acuity, color vision (Ishihara plates), pupillary exam (RAPD), confrontation and automated visual field, dilated fundus exam (disc edema characteristics), OCT RNFL (acute thickening, later thinning)
02
Emergent ESR, CRP, CBC; temporal artery palpation; if any GCA features (age > 70, headache, jaw claudication, scalp tenderness, ESR > 50) or pale disc edema, start high-dose IV methylprednisolone 1 g/day x 3 days then oral prednisone 1 mg/kg/day and arrange temporal artery biopsy within 1 week
03
For NAION: there is no proven effective acute treatment that recovers vision; oral corticosteroids (prednisone 80 mg taper over 6 weeks) controversial — Hayreh observational study showed benefit but not confirmed by RCTs; some specialists offer in select acute cases (< 2 weeks)
04
Optimize all vasculopathic risk factors: blood pressure (avoid nocturnal hypotension — switch evening antihypertensives to morning), diabetes (HbA1c < 7), lipids (statin), smoking cessation, weight loss
05
Sleep study (polysomnography) for all patients to detect obstructive sleep apnea; aggressive CPAP therapy if confirmed (reduces fellow-eye involvement)
06
Discontinue PDE5 inhibitors (sildenafil, tadalafil, vardenafil) — possible association with NAION
07
Aspirin 81 mg daily — controversial benefit but commonly recommended for vasculopathic risk reduction
08
Low-vision rehabilitation: magnifiers, prism glasses, eccentric viewing training, occupational therapy for ADLs, driving evaluation
09
Ophthalmology and primary care follow-up every 3–6 months; vigilance for fellow-eye involvement (urgent re-evaluation if new symptoms)

Which Department to Visit?

You can visit our Göz Hastalıkları department for these complaints. Our specialist physicians will create the most suitable treatment plan for you.

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