What does a 20/20 vision mean?

I was told that I have a 20/10 vision on one eye and 20/15 on the other. I was wondering what that means? So, here it goes: the first number is your ability to see at a distance and the second number is the ability of a normal person to have the same vision. Thus, 20/10 means that what a normal person can see at a distance of 10 feet, you can see at 20 feet.

Here is a curious fact that I learnt on CBS news today – the vision of a typical dog is 20/75. Dogs are also red-green colorblind – they see red, green, yellow and orange as shades of yellow and blue and violets as shades of blue. Researchers know about this by examining the eye cells of the dogs – dogs have 2 photo-receptors (or cones) instead of 3 that we humans have. 

~ by manand76 on April 23, 2008.