11

It’s possible for your eyes to be sunburned. Prolonged sun exposure eventually leads to a thickening of the eye tissue, which might require eye surgery.

12

Your retinas perceive the outside world as upside-down. The brain must then flip and make sense of the image.

13

Eye colour – or our perception of it – can change with lighting conditions. Neither blue nor green pigments are present in the human iris or ocular fluid.

14

Octopus eyes have no blind spot and evolved separately from vertebrate eyes. This is an example of convergent evolution.

15

Up until 10,000 years ago, brown was the only known human eye colour. This changed when a person living by the Black Sea developed a genetic mutation that made their eyes blue.

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