Anthocyanins may also improve eyesight by other mechanisms. In a French study conducted in 1964, researchers vision-tested 36 people for their ability to adapt to light and dark both before and after taking bilberry anthocyanins. For several hours after supplementation, their eyesight improved significantly, although the effect wore off within 24 hours. A recent Japanese study found that people taking 50 mg, but not 20 mg, black currant anthocyanins adapted better to the dark and had less eye fatigue than those in the placebo group.