Anterior Ischemic Optic Neuropathy Clinical Presentation

• Visual loss is painless in at least 90% of patients with nonarteritic anterior ischemic optic neuropathy (NAION). The vision loss is noticed upon awakening, perhaps due to nocturnal hypotension. NAION can occur after procedures such as spinal fusion surgery. Risk factors for NAION after spinal fusion surgery include obesity, male sex, Wilson frame use, longer anesthetic duration, greater estimated blood loss, and decreased percent colloid administration.^[5]
• Patients with arteritic anterior ischemic optic neuropathy (AION) often have symptoms other than visual loss, such as malaise, headache, scalp tenderness and tender temporal arteries, jaw pain on mastication (jaw claudication), generalized muscle aches, and swelling.
• The earlier manifestations of arteritic AION include malaise, weight loss, fever, vague abdominal or GI pains, and anorexia.
• Late manifestations of arteritic AION, often years later, include a much higher incidence of abdominal aortic aneurysm.

• Nonarteritic anterior ischemic optic neuropathy

  • Nonarteritic anterior ischemic optic neuropathy has typical findings of visual loss and field loss in an otherwise asymptomatic individual.
  • A small cup disc ratio is usually noted. Initially, the optic disc is swollen and pale, often in a generalized or diffuse manner.
  • Sectorial disc edema, especially of the superior disc, is classic.
  • Visual loss with nonarteritic anterior ischemic optic neuropathy is not usually as severe as with arteritic anterior ischemic optic neuropathy, but vision loss as severe as no light perception has been described.
• Arteritic anterior ischemic optic neuropathy

  • In patients with arteritic anterior ischemic optic neuropathy, the disc is classically described as chalky white, pale, and swollen.
  • Ischemia in multiple vascular territories is not uncommon (eg, central retinal artery occlusion, choroidal infarction, anterior segment ischemia, extraocular muscle ischemia causing diplopia).
  • The temporal arteries may be quite prominent, ropey, and tender.
  • Oral, tongue, or even scalp ulcers may rarely be seen.

Anterior ischemic optic neuropathy is an ischemic disease, but the cause is yet to be found definitively. In the nonarteritic form, atherosclerosis is assumed to be the basis, with its effect on the circulation of the optic nerve head. The posterior ciliary arteries feed the optic nerve head, and, despite variable results in animal primate models with ligation of the posterior ciliary arteries, their susceptibility to atherosclerosis and arteriosclerosis in a widespread manner seems to be the underlying cause. In the arteritic form, the basis for the ischemia is identical in pattern, with a giant cell arteritis involving most of the orbital vessels, including the central retinal artery, and the posterior ciliary arteries. Involvement of the branch retinal arterioles is rare presumably because of the lack of internal elastic lamina.

• Elucidating the genetic predisposition to giant cell arteritis has yet to be completed but has promise. Incidence in families of Scandinavian origin is high, and genetically determining persons who are predisposed to this disorder may be possible. Human leukocyte antigen (HLA) haplotypes may also provide some interesting relationships, as there are very rare instances of giant cell arteritis in patients with true rheumatoid arthritis. The proximity of the gene locus in these 2 diseases seems to preclude the expression of both diseases in the same individual.
• According to Miller's edition of Walsh and Hoyt's Clinical Neuro-ophthalmology, the causes and associated conditions of anterior ischemic optic neuropathy are as follows:^[6]

  • Vasculitides
    • Giant cell arteritis
    • Polyarteritis nodosa
    • Systemic lupus
    • Buerger disease
    • Allergic vasculitis
    • Postviral vasculitis
    • Postimmunization
    • Syphilis
    • Radiation necrosis
  • Systemic vasculopathies
    • Hypertension
    • Atherosclerosis
    • Diabetes mellitus
    • Migraine
    • Takayasu disease
    • Carotid occlusive disease
  • Hematologic
    • Polycythemia vera
    • Sickle cell disease (trait)
    • Acute hypotension (shock)
    • Glucose-6-phosphate dehydrogenase deficiency (G-6-PD)
  • Ocular
    • Postcataract (possibly)
    • Low-tension glaucoma