7-21: Ischemic Optic Neuropathy

Anterior ischemic optic neuropathy—due to inadequate perfusion of the posterior ciliary arteries that supply the anterior portion of the optic nerve—produces sudden visual loss, usually with an altitudinal field defect, and optic disk swelling (eFigure 7–64). In older patients, it may be caused by giant cell arteritis (arteritic anterior ischemic optic neuropathy). The predominant factor predisposing to nonarteritic anterior ischemic optic neuropathy, which subsequently affects the fellow eye in around 15% of cases, is a congenitally crowded optic disk, compromising optic disk circulation. Other predisposing factors are systemic hypertension, diabetes mellitus, hyperlipidemia, systemic vasculitis, inherited or acquired thrombophilia, interferon-alpha therapy, obstructive sleep apnea, and phosphodiesterase type 5 inhibitors. Diabetic papillopathy is a cause of chronic (possibly ischemic) optic disk swelling that generally has a better visual outcome. Rarely, an optic neuropathy that can be difficult to differentiate from nonarteritic anterior ischemic optic neuropathy, but typically affecting both eyes simultaneously and having a more chronic course, develops in patients taking amiodarone.

Posterior ischemic optic neuropathy, involving the retrobulbar optic nerve and thus not causing any optic disk swelling, may occur with severe blood loss; nonocular surgery, particularly prolonged lumbar spine surgery in the prone position; severe burns; or in association with dialysis. In all such situations, there may be several contributory factors.

TREATMENT

Arteritic anterior ischemic optic neuropathy necessitates emergency high-dose systemic corticosteroid treatment to prevent visual loss in the other eye. (See Central & Branch Retinal Artery Occlusions, above, and Polymyalgia Rheumatica & Giant Cell Arteritis, Chapter 20.) Similar treatment is required in anterior ischemic optic neuropathy due to systemic vasculitis, which may also be classified as arteritic anterior ischemic optic neuropathy. It is uncertain whether systemic or intravitreal corticosteroid therapy influences the outcome in nonarteritic anterior ischemic optic neuropathy or whether oral low-dose (∼81 mg daily) aspirin reduces the risk of fellow eye involvement. In ischemic optic neuropathy after nonocular surgery, treatment of marked anemia by blood transfusion may be beneficial.

WHEN TO REFER

Patients with ischemic optic neuropathy should be referred urgently to an ophthalmologist.

WHEN TO ADMIT

Patients with ischemic optic neuropathy due to giant cell arteritis or other vasculitis may require emergency admission for high-dose corticosteroid therapy and close monitoring to ensure that treatment is adequate.