Xanthopsia is a color vision deficiency in which there is a dominantly yellow bias in vision due to a yellowing of the optical media of the eye. The most common causes are digoxin's inhibitory action on the sodium pump, and the development of cataracts which can cause a yellow filtering effect.
It has been suggested that Van Gogh contracted Xanthopsia as a result of digoxin consumption. Digoxin is a medication derived from digitalis and used to treat various heart conditions. This theory claims Xanthopsia as the cause of the yellow tinting exhibited by many of his works.