TillieTrotter Wrote: ------------------------------------------------------- > Excuse my ignorance Keef, what is acuity? Basically, it's the sharpness / distance of vision... When you look at a snellen test in the opticians (the letters on the chart), most people can see that there are letters there, but can't necessarily pick out what the letter is, that will judge their acuity.... In America, perfect acuity is 20-20. Here it's 6-6 meaning you can see from a distance of 6 metres what you "should be able to" If you could only see the top letter, you'd be 6-60, meaning that you can see from 6 metres what you should be able to see from 60... If you can't see the top letter, you're getting towards being registerable as blind. See HERE for a better explanation. See HERE for a thing about Madeleine McCann, it has a picture of her eye, so you'll see what I mean by the key hole effect... I have the same thing in both eyes, but my eyes are so dark you don't really notice. Sorry to have gone way off the topic again :-S