‘Eat your carrots – they’ll help you to see in the dark,’ parents have urged their children for generations. And it’s no old wives’ tale; carrots are the one of the highest vegetable sources of vitamin A and its precursors alpha-carotene and beta-carotene, all potent antioxidants which are essential for good vision. Both alpha- and beta-carotene are converted to vitamin A in the liver, and the retina can then convert …