• Question: what happens to your eye when your sight gets worse?

    Asked by kicking kacey... to Chris, Josh, Rebecca, Rob, Susan on 16 Jun 2015.
    • Photo: Chris Armstrong

      Chris Armstrong answered on 16 Jun 2015:

      Not an optometrist.

      But I believe, in certain cases at least, that the muscles surrounding the lens can no longer adapt the focal distance in the same way. Meaning you lose range in your vision. Theres other ways that your vision deteriorates but that’s at least one reason.

      However if you’ve lost range you can make a small pinhole with your fingers, look through it, and gain clarity.

    • Photo: Rebecca Dewey

      Rebecca Dewey answered on 16 Jun 2015:

      In a healthy eye, the lens gets stretched and flexed by the muscles around it to create a fatter lens for looking at / focussing on closer distances and a narrower lens for looking /focussing further away. As someone gets older, the lens becomes more rigid / less flexible and these muscles become weak. Therefore the eye becomes limited in the range of distances that it can focus on.

      There are diseases where cells in the retina die and do not get replaced, and so a person can have gaps in their vision. Other diseases can occur where people have deposits that build up on different layers of the eye, such as the macula, or cloudiness in the lens (cateract). Changes in pressure of the fluid in the eyeball can damage the optic nerve (glaucoma). Most of these last few are caused by disease and can be treated if caught early.

    • Photo: Susan Cartwright

      Susan Cartwright answered on 16 Jun 2015:

      – Treat this answer with caution. I am not an opthalmologist. –

      There are many different processes that make your vision deteriorate. Short-sightedness (myopia) develops when the eyeball is too long, so that light coming in is focused to a point in front of the retina. In most myopic people, the condition starts in childhood and gets worse as they get older, before stabilising when they become adults.

      In some people, such as me, the cornea (the surface layer of your eye) is misshapen, giving rise to inability to focus all light to the same point – without my contact lenses, I see halos round bright lights. This condition usually appears in young adulthood (I was late, at about 35) and sometimes gets worse over time as the shape of the cornea deteriorates. It can be corrected in most cases by wearing hard contact lenses (that’s me), but if it’s very bad you may need a cornea transplant.

      Older people lose the ability to focus on nearby objects, probably because the lens gets less flexible, and/or the muscles that control it weaken. This is why most older people need reading glasses.

      In some older people, opaque crystals, called cataracts, develop in the transparent lens of the eye. This obviously makes vision much worse, eventually causing blindness. Nowadays it is fixed by a small operation in which the natural lens of the eye is removed and replaced by a plastic one.

      Some vision problems also arise from problems with the retina, which is the bit at the back of the eye that captures the image. For example, people with diabetes can suffer damage to the retina resulting from poor blood flow, which causes problems with the small blood vessels supplying the retina. There are many other conditions affecting the retina.

      So, you see, there is not one answer to your question but many. That’s why opthalmology is a specialised branch of medicine.

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