Objective: To investigate systematically the natural history of visual outcome in nonarteritic anterior ischemic optic neuropathy (NAION).
Design: Cohort study.
Participants: Three hundred forty consecutive untreated patients (386 eyes) with NAION, first seen in our clinic from 1973 to 2000.
Methods: At first visit, all patients gave a detailed ophthalmic and medical history and underwent a comprehensive ophthalmic evaluation. Visual evaluation was done by recording visual acuity, using the Snellen visual acuity chart, and visual fields with a Goldmann perimeter. The same ophthalmic evaluation was performed at each follow-up visit.
Main outcome measures: Natural history of visual acuity and visual field outcome in NAION.
Results: Of the 386 eyes, 332 had 8 weeks or more of follow-up from the initial visit. At the initial visit, in eyes seen < or =2 weeks from onset of symptoms, 49% had visual acuity of > or =20/30 and 23% had < or =20/200; in these eyes, 38% had minimal to mild visual field defect and 43% marked to severe defect. In those who were first seen < or =2 weeks after onset with visual acuity < or =20/70, there was improvement in 41% at 6 months and in 42% at 1 year after the initial visit. Two years after the initial visit, there was deterioration in 9% of eyes with initial visual acuity of > or =20/60, and in 18% of those with initial visual acuity of < or =20/70. In those who were first seen < or =2 weeks of onset with moderate to severe visual field defect, there was improvement in 26% at 6 months and 27% at 1 year after the initial visit. Two years after the initial visit, 27% of eyes with initial minimal to mild field defects showed worsening, as did 19% of those with moderate to severe defects.
Conclusions: About half of the eyes with NAION presented with almost normal visual acuity (20/15 to 20/30) at the initial visit. Thus, the presence of normal visual acuity does not rule out NAION. Visual acuity and visual fields showed improvement or further deterioration mainly up to 6 months, with no significant change after that.