Not so blindingly obvious

CATARACTS are relatively common in people who live to a ripe old age. They are sometimes seen in animals that live in zoos as well, but in the wild they are almost unheard of. The reason is simple. Losing eyesight is in effect a death sentence for a wild animal that must find its own food and, should that animal live long enough to develop the disease, starvation or predation would quickly follow. But cataracts unrelated to age are surprisingly common in birds living near the site of the Chernobyl nuclear disaster in 1986.