Color vision deficiencies in two cases of digoxin toxicity

Color vision deficiencies are a common sign of digoxin intoxication and color vision testing can be used to diagnose digoxin toxicity. We tested two patients, a 79-year-old man and a 61-year-old man, with digoxin toxicity by means of the Farnsworth-Munsell 100-hue test, AOH-R-R plates, and Ishihara plates. Initial testing disclosed both red-green and blue-yellow color vision deficiencies. These improved when digoxin levels diminished. The deficiencies were superimposed on preexisting acquired and congenital deficits. As serum digoxin levels decreased, the color vision deficiencies lessened on all three tests. The Farnsworth-Munsell 100-hue test gave the best quantifiable measure of color vision deficiencies, but proved difficult to use for routine bedside testing.