Eye Conditions

Refractive Errors

For the eye to present a clear image, the light rays entering the eye need to come to focus on the back of the eye. In 35% of people the rays of light do not focus on the back of the eye, giving a blurred image at the brain. This is correctable by glasses or contact lenses and is known as a refractive error. Refractive errors can be the result of a number of factors, which include:The curvature of your corneaThe optical strength of your lensThe length of your eye
The three categories of refractive errors are: myopia (short sightedness), hypermetropia (long sightedness), and astigmatism. All of these are usually able to be corrected by laser surgery.

Myopia (Short-sightedness)
Myopia is caused by one or a combination of the following:Steep corneaLong eyeballPowerful lens
Consequently light rays focus before, instead of directly on the retina.
Short sighted people are able to see close up objects clearly, but objects in the distance are blurry and indistinct. People with moderate to high levels of myopia are unable to see anything of real value without their glasses.

Hypermetropia (Long-sightedness)
Hypermetropia is caused by one or a combination of the following:Flat corneaShort eyeball
Consequently light rays are focused behind instead of on the retina.
Long sighted people are able to see images in the distance more clearly than they can see images at close. Though most hypermetropic people are unable to see at either distance clearly without their glasses.

Astigmatism
Astigmatism means that the front of the eye is not entirely spherical like a soccerball, but shaped more like a football, (ie. it is not equally curved in all places). This means that the rays of light are bent unequally, therefore giving a distorted or blurred image at all distances.
Astigmatism can be found either alone, or in conjunction with myopia or hypermetropia.

Presbyopia
Presbyopia occurs in all adults approximately 45 years or older. Presbyopia is a natural aging process of the lens inside the eye. This means that distance vision will be unchanged, but near vision will become blurry.
People who are mildly short sighted will be unaffected by the symptoms of presbyopia, but people who have no prescription, are long sighted or strongly short sighted will suffer from the symptoms of presbyopia.

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