All humans have the ability to see ultraviolet light, but it is passively filtered out by the eye's lens. People who undergo surgery to remove the lens can detect ultraviolet light.
21
Only about 2% of the world population has green eyes.
36
Optical illusions occur when what the eyes see conflicts with what the brain expects.
75
Shark corneas are used in eye transplants and shark bone marrow can be used to graft human bones.
132
The focusing muscles of the eyes move around 100,000 times a day. To give your leg muscles the same workout, you would need to walk 80km (50 miles) every day.
21
When you are looking at someone you love, your pupils dilate, they do the same when you are looking at someone you hate.
1k
Sheep, goats, octopuses, and toads have rectangular pupils.
7
There are glasses which allow a red-green color-blind person to see colors the way everyone else does.
22