1. The cornea – is a clear and transparent structure at the front of the eye which focuses light to the back of the eye.

The cornea is the structure that is treated when someone undergoes laser refractive surgery. The shape and thickness of the cornea is changed by laser to allow the person to see better without glasses or contact lenses.

  1. The lens is another clear structure inside the eye, behind the cornea. The lens focuses the light rays to the back of the eye, the retina. The lens is elastic in nature and can become fatter or thinner to allow the light rays from different distances to be focussed well at the retina.

With age the lens becomes harder and stiffer and so it is not able to focus the light from close objects well. This is known as presbyopia and requires the person who is suffering from it to use a separate prescription for close work.

Also with age, the lens structure becomes more translucent or opaque. When this happens it is known as a cataract. Cataracts are treated with surgery and this is one of the most type of surgeries performed on the eye.

  1. The pupil is a circular hole/opening that allows light to come into the eye. Depending on the light conditions the pupil either enlarges in the dark, to allow more light in, or constricts in bright conditions, to let less light in. The size of the pupil is controlled by the iris muscle.
  2. The iris is the coloured part of the eye and is a muscle that controls the size of the pupil.
  3. The retina is like a camera film. It has numerous light detecting cells (about 100 million) which are which detect and convert this light into messages that go to the brain via the optic nerve. The brain will then interpret these as images.
  4. The macula is a part of the retina which allows us to see fine detail and in colour. It is also responsible for our central vision. The maculais
    what allows us to read, watch tv, use the phone etc. The macula is the size of a pinhead but contains a very high concentration of photoreceptor cells (about 4 million light detecting cells) – the cells which detect light. These cells capture the light focussed on them and then send signals to the brain which interprets them as images. The rest of the retina processes our peripheral (side) vision.

It is changes at the macula which leads to macular degeneration- a leading cause of blindness in the UK.