Earlier quoted context omitted.
Like carrots. The British promulgated the belief that carrots improve eyesight to explain the effective of their aircraft spotters, instead of radar.
You mean to tell me they are not?!! I remember reading that carrots have some nutrient necessary for good eye sight, beta-catorene I believe. I don't think it improves your current eye sight so much as it keeps it from going bad from a lack of it.
"Vitamin A has multiple functions: it is important for growth and development, for the maintenance of the immune system and good vision.[2] Vitamin A is needed by the retina of the eye in the form of retinal, which combines with protein opsin to form rhodopsin, the light-absorbing molecule[3] necessary for both low-light (scotopic vision) and color vision."