Color vision in anterior ischemic optic neuropathy

PURPOSE: The non-arteritic form of anterior ischemic optic neuropathy (AION) is the most common acute optic neuropathy among individuals over the age of fifty, yet little is known about how the disorder affects color vision. We tested the hypothesis that color vision correlates with visual acuity in patients with non-arteritic AION. We also evaluated the patterns of visual field loss in a subgroup of patients who manifested relative sparing of color vision. OBSERVATIONS: Records of forty-five patients with non-arteritic AION who had been evaluated at Duke University over a consecutive four-year period were reviewed retrospectively. Statistical analysis of the relationship between color vision and visual acuity was carried out using a linear regression model. Color vision tended to correlate with acuity with respect to visual acuities between 20/16 and 20/63. However, nine patients were identified in whom color vision was relatively spared in comparison with acuity. Most of the affected eyes in this subgroup had a distinctive pattern of visual field loss consisting of a dense, steep-walled cecocentral defect centered below the horizontal meridian. CONCLUSIONS AND IMPORTANCE: In patients with non-arteritic AION, color vision tends to correlate with visual acuity for acuities better than 20/70. Sparing of color vision relative to acuity, a heretofore unreported finding in AION, occurs in approximately 15% of cases. Sparing of color vision reflects damage to foveal projections coupled with preservation of extrafoveal macular projections. The results of color vision testing in patients with non-arteritic AION help to differentiate this condition from other optic neuropathies such as optic neuritis.