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THE EYE AND MYOPIA (Short sightedness)
In the majority of eyes, light coming from a distant source entering the eye is focused by the cornea (clear dome which forms the outer covering of the pupil) onto the central point of the retina. Unfortunately, not all eyes perform this function. In many cases the cornea is too steep, too thick or the eye is longer than necessary causing the rays of light to focus in front of the retina leaving the distant object blurred. An individual with this problem is often termed ‘short sighted’ because their near vision is not as affected as their distance vision allowing them to see close objects clearly
Who gets myopia?
Short sight normally develops in childhood or adolescence and is often first noticed at school. Glasses may need to be worn all the time or, watching TV or sports. It can progress over the next few years and normally stops getting worse in adults. The risk of developing myopia is increased if there is a family history of it and there may also be a link between myopia and prolonged close-up work, such as reading or sitting close to the television, although there is little scientific evidence for this. Myopia can be associated with certain types of cataracts, where the lens becomes cloudy. It can also be caused by a condition called keratoconus, in which the cornea thins and becomes more curved.
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When the cornea is not powerful enough to bend light from a distant object to a single point of focus on the retina the eye is termed Hyperopic (or Hypermetropic). This can be caused by a cornea that is too flat, too thin or an eyeball that is too short.
Young hyperopes can use the focusing power of their lens to clarify the image. Requiring energy, this process can cause headaches and eyestrain. As the image gets closer the amount of effort and energy required increases until at close range the blurring and headache symptoms can be pronounced. This blurring at near has given rise to the term ‘long-sighted’ as it is at close range that sufferers first report problems.
Who gets Hyperopia?
Like myopia, hyperopia can occasionally run in families, however, due to patients’ ability to compensate for the symptoms it is usually only at an eye examination that it can be identified. Early identification of a hyperopic individual is important in limiting their symptoms and stopping complications that can arise from it such as Squints/Lazy eyes. Glasses may need to be worn all the time or just for close work, such as reading, writing or computer use. In older people, as re-focusing becomes more difficult, distance vision may also become blurred.Laser Eye Surgeons
Many people have heard of Astigmatism, but, unfortunately many are under the misconception that it is a rare condition or at least a pathological one.
The cornea is often described as being rugby ball shaped as it has two different curvatures, one longer than the other, at 90 degrees to each other. Light passing into the eye through such a cornea is distorted into a pattern often described by astigmats as being like 'double vision'
Who suffers from Astigmatism?
Almost every eye in the world has some form of astigmatism. What causes the visual blurring is its magnitude. The larger the difference between the two curves the more distorted the light and the more blurred the persons vision.
Presbyopia generally occurs between the age of 40 and 50 years of age and warrants the use of corrective near vision spectacles. The condition is often confused with Hyperopia because the initial symptoms are the similar including eye strain, headaches and a reduction in vision at near.
As has already been stated the eye relies on the internal muscles and flexible lens to fine tune the focus on objects and the closer the target is, the more flexibility is required. As the eye ages this flexibility wanes and the effectivity of the muscles diminishes. Individuals often note this when they need to read small print at close range. They feel themselves conciously staring and forcing the muscles to make the image clear leading to eyestrain and headaches
Who suffers from Presbyopia?
Unfortunately, Presbyopia is as inevitable as death and taxes, affecting almost everyone at some point in their life. In the western world this tends to be after 45 years of age.