ADD-ONS / OTHER VASCULAR DISORDERS

Ischemic optic neuropathy (ION)

David Goldemund M.D.
Updated on 06/01/2024, published on 11/07/2023

  • Ischemic Optic Neuropathy (ION) is a condition characterized by significant visual impairment due to ischemia of the optic nerve
  • ION is the second most common optic nerve disease after glaucoma in patients over 50 years of age
  • there are two distinct types of ION (anterior and posterior) based on the arteries involved
    • posterior ischemic optic neuropathy, PION
      • rare lesion of the retrobulbar portion of the optic nerve
      • likely caused by occlusion of one or more pial branches
      • uni- but more commonly bilateral involvement
      • no optic disc edema
    • anterior ischemic optic neuropathy, AION
      • more common
      • posterior ciliary arteries are affected
      • optic disc edema

Ocular vascular syndromes

Ocular vascular disorders
Ischemic optic neuropathy (ION)
  • anterior (AION)
    • arteritic
    • non-arteritic
  • posterior (PION)

Central retinal vein occlusion (CRVO) → more
(the most common retinal vascular occlusive disorder)
  • non-ischemic (venous stasis retinopathy – VSR) – usually benign condition [Hayreh, 1983]
  • ischemic (hemorrhagic retinopathy – HR) – the risk of severe visual impairment

Hemi-central retinal vein occlusion (HCRVO)
  • non-ischemic (venous stasis retinopathy)
  • ischemic (hemorrhagic retinopathy)

Branch retinal vein occlusion (BRVO)
  • major BRVO
  • macular BRVO

Central retinal artery occlusion (CRAO)
  • arteritic CRAO (giant cell arteritis) – approx. 5%
  • non-arteritic permanent CRAO (NA-CRAO)
  • non-arteritic transient CRAO
  • CRAO with cilioretinal artery sparing (central vision maintained to varying degrees)

Branch retinal artery occlusion (BRAO)
  • permanent BRAO
  • transient BRAO

Cilioretinal artery occlusion

Anatomy

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Etiopathogenesis

Etiology

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Pathogenesis

  • vascular occlusion and hypoperfusion are primarily involved in ischemic optic nerve damage
  • nocturnal hypotension and mechanical factors may play an important role (compression due to ischemic edema or external compression completes the vicious circle, leading to irreversible visual impairment)

Clinical presentation

Anterior ischemic optic neuropathy, AION

  • visual impairment
    • typically unilateral, sudden, and permanent
      • transient visual loss is unusual in the nonarteritic form (NAION), amaurosis fugax may precede permanent visual loss in the arteritic form (AAION)
    • unilateral visual loss accompanied by decreased visual acuity (typically <20/200) or visual field defect (usually inferior altitudinal scotoma)
    • painless in NAION
  • relative afferent pupillary defect (RAPD, Marcus-Gunn pupil)
    • “relatively” impaired response to light compared to the unaffected eye
  • optic disc edema   Papilledema in anterior ischemic optic neuropathy
    • commonly chalky-white pallor in AAION and hyperemic swelling in NAION
    • accompanied by hemorrhages or cotton-like ischemic deposits in the adjacent retina
    • edema progresses relatively rapidly to either total or partial sectoral atrophy
  • the development of nonarteritic ION in the fellow eye is reported in 25-40% of patients, whereas new attacks in the already affected eye are rare

Posterior ischemic optic neuropathy, PION

  • rare compared to AION
  • visual impairment
    • sudden and permanent, painless loss of vision, often bilateral
    • due to hypotension or severe anemia
  • NO optic disc edema
  • afferent pupillary defect present in unilateral lesions

Diagnostic evaluation

A rapid identification of the etiology is crucial because it determines the therapeutic management; corticosteroids must be promptly administered in cases of AAION

  • clinical examination
    • best corrected visual acuity (BCVA) and visual field testing
    • test reaction to light, motion, finger counting, oculomotor nerve function
    • search for temporal artery anomalies Local findings in temporal (giant cell) arteritis
  • fluorescein angiography (FA)
    • poor, delayed, or absent choroidal filling is characteristic for arteritic AION
  • differentiation of the AION and PION
    • in AION, papilledema is present in the first 4 weeks after onset
    • in PION, fundoscopy is normal; the pallor of the disc develops within ~ 8 weeks
    • after 4-8 weeks, optic disc atrophy develops in both forms
    • an altitudinal visual defect and unilateral involvement are typical for AION
  • early diagnosis of the arteritic form (especially temporal arteritis) is essential; signs of arteritis include:
    • older age, rapid progression
    • headaches
    • swollen and pale optic disc
    • systemic symptoms (loss of appetite, myalgia, weight loss, fatigue, fever), periorbital pain, jaw claudication
    • ↑ ESR (up 70-120mm/min) and ↑ CRP  (97% specificity if both are elevated), elevated platelet count
    • the diagnosis of arteritis is confirmed by superficial temporal artery biopsy
  • other imaging methods
    • MRI may differentiate between AAION and NAION; high-resolution T1 shows optic nerve disc enhancement (bright spot sign) + intravitreal protrusion in AAION   (Remond,2017)
    • ultrasound shows characteristic dark wall swelling (halo) and acute occlusion in active AAION
    • Optical Coherence Tomography (OCT) may also provide clinical evidence of the optic nerve ischemia
  • laboratory studies for other systemic predisposing factors (vascular risk factors, CBC, etc.)

Differential diagnosis

  • optic neuritis
  • infiltrative optic neuropathies
  • optic nerve inflammation associated with syphilis or sarcoidosis
  • anterior orbital lesions with optic nerve compression
  • diabetic papillopathy

Management

Nonarteritic form

Arteritic form

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Ischemic optic neuropathy (ION)
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