Low-contrast letter charts to detect subtle optic [corrected] neuropathies.

We performed visual contrast sensitivity testing with Regan's low-contrast letter charts on 30 patients with optic neuropathies and good Snellen visual acuity. Results of this testing were compared with color vision and the presence of an afferent pupillary defect. Regan's low-contrast letter charts were found to be 93% sensitive for detecting subtle optic neuropathies, with the apparent false-negative findings being readily explainable. Color vision testing was abnormal in only 49% of eyes with known optic neuropathies.