The use of colour vision measurement in the diagnosis of digoxin toxicity.

Colour vision has been measured, using the Farnsworth-Munsell 100-Hue test, in control subjects and in patients taking digoxin. In 10 patients with digitalis toxicity, of whom only two described symptomatic abnormalities, colour vision was impaired compared with that of both control subjects and non-toxic patients who had been taking digoxin for more than two months. Withdrawal of digoxin from toxic patients led to improved colour vision. Colour vision scores correlated well with (a) log plasma digoxin concentrations, and (b) various measures of the pharmacodynamic effects of cardiac glycosides on cation transport in the patients' own erythrocytes. These results suggest that colour vision assessment may be of use in screening for digitalis toxicity at the bedside and in assessing the degree of digitalis intoxication in an individual patient as an aid to clinical research.