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Short Sight - Myopia

myopia


A refractive error is an eyesight problem. Refractive errors are a common reason for reduced visual acuity (level of eyesight). Refraction refers to the bending of light. In terms of the eye. A refractive error means that the eye cannot focus light on to the retina properly. This usually occurs either due to abnormalities in the shape of the eyeball, or because age has affected the workings of the focusing parts of the eye.

There are four types of refractive error:

  • Myopia (short sight).
  • Hypermetropia (long sight).
  • Astigmatism (a refractive error due to an unevenly curved cornea).
  • Presbyopia (an age-related refractive error).

The light rays have to be focused on a small area of the retina; otherwise what we look at is blurred. The cornea and lens have the job of focusing light. More bending (refraction) of the light rays is needed to focus on nearby objects, such as when reading. Less bending of light is needed to focus on objects far away.

What is short sight (myopia)?

Myopia occurs when light is focused in front of the retina. It occurs because either the eyeball is too long, or because the cornea is too curved. Despite maximum flattening of the lens, the eye is not able to focus the light rays further back, and on to the retina.

People with short sight are not able to see distant objects clearly. Near objects (for example, when reading a book) can often be seen well.

What causes short-sightedness (myopia)?

Myopia tends to happen in children and young teenagers. It often runs in families. Temporary short-sightedness can also occur with certain illnesses - for example, in diabetes.

What are the symptoms?

The main symptom is a difficulty with distance vision. The earlier myopia starts, the more severe it is likely to become. Some children do not realize at first that their vision is not as good as it should be. They may be able to read books and do close work well. However, seeing distant objects such as the board at school may become difficult. They may think this is normal and not tell anyone. Schoolwork may suffer for a while before the condition is identified and treatment provided.

Children usually have a routine preschool or school-entry vision check. Your child's teacher may notice that they are having difficulties in class reading the board.

Are there any complications?

The vast majority of people with short sight have no other associated problems.

However, people with severe short sight have a slightly increased chance of developing glaucoma, detached retina and macular degeneration. These are serious eye conditions. So regular eye checks are advisable.

What is the treatment for short-sightedness?

Glasses

The simplest, cheapest and safest way to correct short-sightedness is with glasses. Concave prescription lenses (called minus lenses) are used to bend light rays slightly outwards. Glasses are seen as more acceptable these days, and younger people may even regard them as a fashion accessory.

Contact lenses

These do the same job as glasses. Many different types of contact lenses are available. Lenses may be soft or rigid gas-permeable. Contact lenses can be daily disposable, extended wear, monthly disposable, or non-disposable. Your optometrist can advise which type is most suitable for your eyes and your short sight prescription. Contact lenses often work out more expensive than glasses and they require more care, and meticulous hygiene.

Surgery

Laser eye surgery is expensive but offers the chance to restore normal sight permanently. The cure is usually instant and the procedure is generally painless.
Several types of laser surgery have been developed. These include: LASIK, PRK and LASEK. They are similar because the basic idea is to reshape the cornea using the laser to remove a very thin layer. The reshaped cornea allows the refraction of the eye to be corrected.

LASIK®

LASIK stands for L aser-As sisted I n situ K eratomileusis. This is the most popular form of laser eye surgery. The laser is used to lift and remove a very thin layer of the cornea. This helps to flatten the cornea so that the light rays can be focused further back, and on to the retina.

PRK® PRK stands for P hoto-R efractive K eratectomy. It is an older surgical operation, that has mostly been replaced by newer techniques.

LASEK® LASEK stands for LA ser S ub-E pithelial K eratomileusis. It is an improved form of PRK with some similarities to LASIK. Most of the outer layer of the cornea (the epithelium) is left intact.

How often do I need an eyesight test?

This depends on your age, your family history and any pre-existing medical conditions. As a guide, if you fall into the high-risk group, you should have at least an annual (yearly) eye examination if you are over 60 years of age. If you are over 50 years of age it should be every two years, and over 40 years, with risk factors, then an eyesight check is recommended at least every three years.

If you fall in the low risk group and are aged between 19 and 40, an eye test is needed every 10 years. Between the ages of 41 and 55, it is recommended that you see an optometrist five-yearly. At any age between 56 and 65, two-yearly checks are needed, dropping to annual checks in low-risk people who are 65 or more.


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