Anterior ischemic optic neuropathy, or AION, is sudden vision loss caused by reduced blood flow to the front portion of the optic nerve. Though less familiar than stroke, AION is sometimes called an eye stroke and shares many features with cerebrovascular disease.
Two Main Types
Nonarteritic AION is by far the most common form, usually affecting people over fifty. Arteritic AION, less common but more dangerous, is caused by giant cell arteritis and can rapidly affect the second eye if not treated urgently.
Nonarteritic Presentation
Patients typically wake with painless, sudden vision loss in one eye, often noticed first thing in the morning. The vision loss is usually altitudinal, meaning the upper or lower half of vision is affected. Color perception may dim.
Arteritic Red Flags
Patients over age fifty with new headaches, scalp tenderness, jaw pain when chewing, fever, weight loss, or aches in the shoulders or hips should be evaluated urgently. These can signal giant cell arteritis, which is a medical emergency.
Diagnosis
Examination reveals a swollen optic nerve with characteristic appearance. Visual field testing maps the deficit. Blood tests including ESR and CRP help identify giant cell arteritis. Sometimes a temporal artery biopsy is performed to confirm.
Treatment
Arteritic AION requires immediate high-dose corticosteroids to prevent involvement of the other eye. Nonarteritic AION has no established treatment that reverses the damage, but addressing risk factors helps prevent recurrence in the unaffected eye.
Risk Factors and Prevention
Sleep apnea, hypertension, diabetes, and use of certain medications including phosphodiesterase inhibitors have been associated with nonarteritic AION. Identifying and treating these conditions is the foundation of secondary prevention. For detailed information on AION, the American Academy of Ophthalmology offers reliable patient resources.