• Question: how do our eyes work

    Asked by ledw to Christina, Colin, Jess, Samaneh, Steve on 18 Jun 2013.
    • Photo: Jess Bean

      Jess Bean answered on 18 Jun 2013:

      The light receptors in our eyes are crucial in us being able to see.

      Have you learnt about the electromagnetic spectrum? We have light receptors in our eyes which respond to ‘visible light’ (not infrared or UV like some other animals). When the light enters our eyes through the pupil (the black part at the front of our eye) it is focused through the lens in the middle of our eye onto the retina at the back. The light receptor cells (called rods and cones) are on the retina. Cone cells allow us to see colour, rod cells allow us to focus on objects. These cells send messages through other cells to our brain, allowing us to see. (Apparently a human eye has more than a million light-sensitive cells!).

    • Photo: Christina Pagel

      Christina Pagel answered on 18 Jun 2013:

      This isn’t quite answering the question (partly because Jess has answered it so well already) but something that I think is really cool is that blind people can learn to use echos from clicks (like bats!) to move around and judge where things are – and that brain scans have shown that this trains exactly that part of the brain which would be used to interpret what comes through the eyes for people who can see!

    • Photo: Steven Gardner

      Steven Gardner answered on 19 Jun 2013:

      Jess has given a very good answer, but she’s left out a rather large and important part (don’t worry Jess, even in vision science departments everyone like to focus on the retina!).

      Rod cells are not for focussing, they are actually for your peripheral vision (that’s your vision around the central sharply focussed bit) and for vision in low light. They don’t measure colour, which is why in low light most things appear in shades of grey. In your peripheral vision there are also a few cone cells that fill in the colour of things.

      The focussing is done by the bits at the front of the eye, the cornea and the lens. They focus the light to a point on your retina, giving you sharp vision in the centre. Without light everything you see would be blurry.

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