Question: how does your eye make you see?

Pip Millington answered on 14 Nov 2016:

Good question.

The part of the eye which actually tells your brain what you see is called the retina. It’s a layer just a few cells thick covering the inside of the back of the eye ball. There are lots of light sensitive cells here which send a signal along the optic nerve when they detect light. There are a few different types and these are adapted to detect light differently at different wavelengths (colours). They are spread out in an organised way which forms a map of what you can see. The rest of the eye (lens, iris, cornea, etc) is designed to try and form an exact replica image of what is in front of you on the retina, except that it’s upside down.

The brain then interprets which colour cells detected light in what pattern on the retina and flips the image the right way round so that you can recognise what you are seeing.