• Question: how do eyes work

    Asked by anon-220639 on 12 Jun 2019.
    • Photo: Rebecca Moon

      Rebecca Moon answered on 12 Jun 2019:

      The eye is an amazing, and super complicated organ. Did you know that it takes 3 years at university to study to be an optician, and there is a whole branch of medicine dedicated to treating the eye (ophthalmology). So I could spend 3 or more years telling you how it works, but essentially there are some receptors at the back of the eye on the retina called rods and cones. These detect light and that triggers neuronal impulses which pass along the optic nerves to the brain where the neuronal messages are converted into images. The lens has an important role of focussing the eye and enables us to see both short and long distance. And we have 6 muscles surrounding the eye that moves the eyeball so we can look in different directions. There are nerves from the brain that control this to make sure that the eyes move together, otherwise you’d get double vision (the technical name for double vision is diplopia).

    • Photo: Kaitlin Wade

      Kaitlin Wade answered on 13 Jun 2019:

      Rebecca has answered the question perfectly!

      There’s a really good youtube video here that also explains things well: https://www.youtube.com/watch?v=i3_n3Ibfn1c

    • Photo: Matthew Bareford

      Matthew Bareford answered on 14 Jun 2019:

      Have to say,

      Rebecca has given a brilliant answer here and Kaitlin provided a good video!

    • Photo: Nina Rzechorzek

      Nina Rzechorzek answered on 14 Jun 2019:

      Agreed – I love Rebecca’s succinct description on this – and as she says, the eyes are so complex, you could delve into ever more detail about how they work.

      As someone that works in neurology, I have always been fascinated by the fact that, in developmental terms, the eye is part of the brain, so we include ‘neuro-ophthalmology’ in our training and we perform several reflexes with the eyes during every neurological exam of a patient (FYI pretty much the same reflex tests are performed in human and non-human animal patients).

      Because of the way the eye extends outwards during development (via the optic nerve), it is the only part of the brain that can be seen directly – this happens when the optician uses an ophthalmoscope and shines a bright light into your eye as part of an eye examination. It shows the innermost layer of the eye (the retina), and the nerve carrying visual messages from the retina to the brain (along the optic nerve) are visible in the back of the eye.

      In many neurological diseases, such as multiple sclerosis or stroke, we can see changes in the optic nerve that help with the diagnosis. And if pressure in the brain increases, perhaps due to a brain tumour, we can see this as a swelling of the optic nerve. So changes in the back of the eye can be used in the diagnosis of high blood pressure, diabetes, glaucoma, age-related macular degeneration or genetic diseases, such as retinal dystrophies. As a result, we often consider the eye to be ‘a window into the brain’!

      Really amazing and detailed pictures can now be obtained from the retina using optical coherence tomography (OCT) – a very cool non-invasive research tool:
      https://www.ed.ac.uk/clinical-research-facility/core-services/imaging-and-image-analyis/retinal-imaging

    • Photo: Kate Timms

      Kate Timms answered on 19 Jun 2019:

      Everyone else has given great answers, so I thought I’d add a random fact about our eyes!
      For some reason octopus and squid have evolved to have pretty much exactly the same kinds of eyes as us! This is amazing because our last common ancestor didn’t have those eyes. Which means that our kind of eyes evolved at least twice. We call this convergent evolution and I think it’s pretty neat.

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