A couple of people have asked about cataracts in young kids. They are very common in developing, poor nations largely due to lack of nutrition. Other reasons are dehydration, exposure to the environment and any sort of eye infection even minor ones that go untreated and unnoticed lead to cataracts and blindness. The surgery to clear cataracts is very quick in less than an hour sight is restored to these people and suddenly their world is radically changed because before they lost their jobs and families if they were older all because they couldn't see and now they have their sight. Something I take for granted regularly is these peoples livelihood.
Hope that answers your questions;)