By Dr_Rob-Hicks Published 01/27/2016 13:18:00 | Views: 339

How the eye works

To see clearly, light rays need to be focused on the retina at the back of the eye. This is achieved as the light rays pass through the transparent cornea and then through the fine-focussing lens.

The image formed on the light-sensitive retina is converted into electrical impulses that pass through nerves to the part of the brain responsible for vision. Here, the impulses are interpreted to tell us what we are seeing.

Myopia - or short-sightedness

Problem: the eyeball of short-sighted people is too long when compared to the focussing power of the cornea and lens. This means light rays from objects in the distance are focussed in front of the retina because they have been bent too much by the cornea and lens.

Effects: getting a clear image of distant objects is difficult, whereas the ability to see things close up is fine. Children may start performing poorly in class because they are unable to see and read what's on the blackboard.

Who and when: usually the condition is first noticed in older children and young teenagers. Short-sightedness can run in families, so short-sighted parents are more alert to the possibility of their children having sight difficulties

Short-sightedness can be corrected with a concave lens that makes the light rays diverge and focus accurately on the retina. Sometimes, laser surgery can be used to correct the problem by re-shaping the cornea.

Hypermetropia - or long-sightedness

Problem: the eyeball of long-sighted people is too short when compared with the focussing power of the cornea and lens. This means light rays from objects nearby are focussed behind the retina because they have not been bent enough by the cornea and lens.

Effects: getting a clear image of objects close up is difficult. Long-sighted people have difficulty reading or doing fine close-up work such as model-making or electrical repairs. Younger long-sighted people are able to see objects in the distance because their lens are flexible, but older long-sighted people often find they develop problems seeing objects in the distance clearly because the lens becomes less flexible as we get older. This condition is called presbyopia.

Who and when: long-sightedness may be apparent in very young babies and children who are not interested in small objects. Older children may be reluctant to read because they find it difficult. Adults may find they have difficulty reading or seeing a computer screen clearly. All children should be formally tested before the age of three if there is long-sightedness in the family. If the eyes are not equally affected, problems such as a squint or even loss of vision in one eye may occur if treatment is not given at an early age.

Correction: it can be corrected with a convex lens that makes the light rays converge and focus accurately on the retina. As the lens becomes less flexible with age, a stronger prescription may be needed.

Good advice

It's important everyone has their eyes checked regularly by an optician - every two years is recommended. Not only will this ensure your eyes are given any assistance they need, but it will help keep life in focus too.

 
 
 
 
By Dr_Rob-Hicks 01/27/2016 13:18:00
 
 

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