Color vision tests to identify elevated digoxin levels

The purpose of this study was to determine the usefulness of color vision screening in identifying patients with elevated digoxin levels (greater than or equal to 2.0 ng/ml). Test-retest color vision measurements were obtained on 56 subjects with elevated digoxin levels and 93 non-digoxin subjects. Two tests, the Ishihara and Sahlgren's Saturation Test (SST), identified digoxin levels of 2.9 ng/ml or more. These tests also yielded a high percentage of improved retest scores among subjects with elevated digoxin levels (greater than or equal to 2.7 ng/ml) of more than 4-days duration and a low percentage of improved retest scores among the non-digoxin group. The Ishihara, SST, and other bedside color vision tests may prove useful in the routine monitoring of patients on digoxin therapy, especially those with a high risk for toxicity.