Purpose: To characterize anterior ischemic optic neuropathy (AION) in patients younger than 50 years.

Design: Retrospective study.

Methods: Records of all AION patients seen between 1989 and 2006 were reviewed. Patients younger than 50 years when initial visual loss occurred were included.

Results: Of 727 consecutive patients with AION, 169 (23%) were younger than 50 years (median, 43 years; range, 13 to 49 years; 58% men; 93% White). Involvement was unilateral in 59% of patients and bilateral in 41%. At least one cardiovascular risk factor was found in 74% of patients. Hypercoagulable states and vasculitis were found in 8%. An underlying small or anomalous optic disk was found in 92% of eyes (210/230). Isolated disk anomalies (without systemic risk factors) were present in 26% of eyes. Final visual acuities were 20/40 or better in 64% of eyes and 20/200 or worse in 22%. Among patients with bilateral involvement, final visual acuity was similar in the two eyes in 70% of patients. Anemia and type I diabetes were associated significantly with fellow eye involvement. Recurrent AION in the same eye occurred in 6% of patients.

Conclusions: AION in younger patients is not uncommon and represents 23% of AION patients in a tertiary neuro-ophthalmic service. Except for giant cell arteritis, ocular and systemic risk factors and associated disorders are similar to those described in older AION patients. Younger AION patients have better visual acuity outcomes but a higher risk of fellow eye involvement than older AION patients.