Just a reminder: Take nothing for granted

I don't know what to say. Can you see my jaw on the floor?

One of my daughter's classmates, one of those people that she just really clicks with, is now blind. Last week, we spent 2 hours with him at the TJ tot lot. The next morning he went to Walt Disney World. Exactly one week later, when I was just starting to wonder why he wasn't back, I got an email from his mom explaining, "the last three days he has lost his ability to navigate through even the most familiar environments, to use a computer, or even find food on a plate within inches of his face. "
With no apparent explanation, over less than 1 week he developed thick cataracts and is completely blind in one eye and 95 percent blind in the other. He is 6 years old.

How can that happen?
He is supposed to regain his sight almost to his previous condition after surgery. ... But can they fix something so easily with never even understanding why it happened? And how will he manage for the next month while they try to schedule the operation? How do you explain any of it to a child?
What can the point of any of it be, except to make us look at our lives and appreciate what we have. I painfully watched my own father loose his sight, but that was over years not days. I guess it figures that blindness destroyed a grown man's life, but a 6-year-old child adapts and doesn't seem too much affected by it all.