Two presentations of nonarteritic ischemic optic neuropathy

Nonarteritic ischemic optic neuropathy (NAION) is the most common acute optic neuropathy in adults over the age of 50. Patients affected notice sudden and painless loss of vision in 1 eye, often upon awaking. Studies have found that the opposite eye may be affected in approximately 15% to 20% of cases within a 5-year period. NAION vision loss results from an ischemic event often affecting the short posterior ciliary arteries. This results in optic nerve pallor, nerve fiber layer defects, and corresponding visual field defects.

Two cases of NAION are discussed here. The first patient, a 57-year-old woman, had a 10-year history of visual symptoms, and the second, a 66-year-old man, presented in less than a week after first noticing symptoms. Both had predisposing systemic risk factors and resultant visual field loss and decreased visual acuity.

Predisposing factors for NAION include small cup-to-disc ratios of the optic nerve, obstructive sleep apnea, nocturnal hypotension, diabetes, and other vascular diseases. The vision loss is irreversible, and there is no known effective treatment to prevent subsequent disc atrophy or recurring episodes.