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
Sheep, goats, octopuses, and toads have rectangular pupils.
7
When you are looking at someone you love, your pupils dilate, they do the same when you are looking at someone you hate.
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Poor eyesight (myopia) is associated with higher IQ.
232
The colossal squid has the largest eyes in the world.
4
Shark corneas are used in eye transplants and shark bone marrow can be used to graft human bones.
132
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