Optical illusions occur when what the eyes see conflicts with what the brain expects.
75
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
Our eyes are always the same size from birth, but our nose and ears never stop growing.
266
There are glasses which allow a red-green color-blind person to see colors the way everyone else does.
22
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
The human eye blinks an average of 4,200,000 times a year.
233
There's a woman named Veronica Seider who had vision 20x better than average. She could identify people more than a mile (1.6km) away.
22