21
The visual centres in the brain are located at the lower back part of your head. This is why people with head injuries can sometimes experience temporary blindness.
22
Tetrachromacy is a rare genetic mutation occurring in 2% of women. It gives them an extra retinal cone, allowing them to see 100 million colours.
23
Staring directly into the sun will burn a spot in the retina, causing permanent blindness. This is called solar retinopathy.
24
Iris pigmentation develops over the first year of life. This means our eyes are darker now than they were when we were newborns.
25
Our eyeballs grow just like the rest of our body. At birth, they are roughly 16 millimetres wide; by puberty, they will have grown to a maximum width of 24 millimetres.
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