In the book "Relearning to see" it says that medium UVA and UVB exposure is actually good for the eyes. It also says that the researches about high exposure of fishermen and the connection with cataract is vague, but many scientists now based on these researches blame UVA and UVB mainly for cataract so they advice sunglasses or hats.
An holistic approach says that diabetis,nephritis and bad eating habits and toxic condition can cause cataract. So they suggest a good diet,fasting, Bates' method (sunbathing, palming, cold eye washes etc) and eyebright extract drops. These measures for the early stages of cataract or for prevention otherwise it needs surgery.