Prospective, randomized, placebo-controlled, double-blind testing of colour vision and electroretinogram at therapeutic and subtherapeutic digitoxin serum levels.

In a prospective, randomized, double-blind study with 10 healthy probands, changes in colour discrimination and in the pattern electroretinogram (P-ERG) and visually evoked cortical potentials (P-VECP) were monitored at therapeutic and subtherapeutic digitoxin serum levels. There was a slight increase in the total error score in the Farnsworth-Munsell 100-hue test at 0.1 mg digitoxin per day in comparison with the placebo.