sight

A wise old man's face with glasses
When I was working in the Amazon in South America, we had a lot of people come in to us with eye problems. Many of them just had simple things like short- or long-sightedness and we could help them with eyeglasses. Doubtless for good genetic reasons, there was one particular Amerindian tribe – the Wapisana – who had a very high prevalence of presbyopia – long-sightedness in old age. And that meant that in that whole tribe, almost no-one over the age of thirty could see within hand-distance. And...