Human

You have no mirror behind your retina, so your eyes glow red in a photo instead of green. The red is blood in the back of your eye.

Humans show far more white around the iris than other apes and monkeys, which makes it easy to see where someone is looking.

Your round pupil is the shape most common in animals that hunt in the daytime and go looking for food. Big cats like lions have round pupils too, even though they ambush.

Your eye has a blind spot, one patch at the back with no light sensors at all, where the wiring gathers and leaves for the brain. Draw a dot on the left of a page and a cross about 15 cm to its right, shut your right eye, look at the cross with your left eye and slowly bring the page closer. The dot disappears.

Your blind spot is not in the middle of the back of your eye. It sits about five millimetres over toward your nose from the fovea, the tiny pit where your sight is sharpest.