What are Refractive Errors?
Refractive errors are disorders, not diseases. It means that the shape of your eye does not bend light correctly, resulting in a blurred image. A person with a refractive error has eyes that do not focus perfectly and needs spectacles to see clearly. The common types of refractive error are described below:
MYOPIA (Short-sightedness)
A person with myopia can see near more clearly than far ones and needs to wear spectacles to correct this. Myopia is usually caused by an eyeball that is too long. Far objects are focused in front of the retina and are therefore seen as blurred images.
Myopia is a very common problem among the population. Myopia often progresses throughout the teenage years, when the body is growing rapidly. It may adversely affect their schoolwork, sports performance and social skills. Myopia may even damage vision permanently in young children if not corrected early. Therefore all young children should have regular sight test.
Myopia worsens as the body grows. New spectacles may be needed as often as every six months in children. It stabilizes and increases only marginally in full-grown adults.
Myopia is occurring more frequently and affecting children at a younger age in Malaysia for all races. Looking at text, images and objects too closely is the main environmental factor in myopia. Reading, computer usage, television watching and indoor activities should be moderated and outdoor activities and exercises encouraged.
High Myopia
Myopia is not only about wearing glasses. People with higher degrees of myopia also have a greater risk of complications that can cause blindness. These complications occur later on in life after the age of 40. Examples of these are: a tear in the retina, detachment of the retina from back of the eye and bleeding into the retina (macular degeneration). These may caused a person to see spots, shadows, flashes of light or suffer from blurred vision. Anyone who experiences these symptoms should see an eye specialist without delay.
High myopia may take on an uncommon from of myopia called degenerative myopia. This is often inherited. The degree may deepen rapidly and complications may occur. High myopia is sometimes inherited as part of a medical problem which affects other parts of the body.
Myopia is best treated with spectacles or contact lenses. LASIK treatment and other forms of refractive surgery are also effective and safe. However, the treatment does not prevent the complications of high myopia and is not suitable if the myopia is still progressing.
HYPEROPIA (Long-sightedness)
A long-sighted person may experience difficulty focusing on both near and far objects but suffers greater blurred vision with near objects. Hyperopia is usually caused by an eyeball that is too short or corneal curvature which is too flat which causes objects to be focused behind the retina.
Normally, young children have a mild degree of long-sightedness but this usually disappears by their teen years. Large amounts of undetected long-sightedness in children may cause squints, headaches or a lack of interest in reading. Undetected long-sightedness in adults may cause eyestrains or blurring when doing work up close. This causes reading glasses to be needed at a younger age than usual. Young children with a normal amount of long-sightedness do not need glasses. Long sightedness should not be confused with presbyopia.
PRESBYOPIA
After age 40, the lens of the eye becomes more rigid and does not flex as easily. The result is that it is more difficult to read at close range. This normal aging process of the lens can also be combined with myopia, hyperopia or astigmatism. It occurs at a younger age in long-sighted people. Reading spectacles are then required. Bifocal, multifocal or progressive lenses may be prescribed depending on age, lifestyle and profession.
ASTIGMATISM
Astigmatism usually occurs when the front surface of the eye, the cornea, has an irregular curvature. Normally the cornea is smooth and equally curved in all directions and light entering the cornea is focused equally on all planes, or in all directions. In astigmatism, the front surface of the cornea is curved more in one direction than in the other. This abnormality may result in vision that is much like looking into a distorted, wavy mirror. Usually, astigmatism causes blurred vision at all distances. It is treated with spectacles or contact lenses. LASIK and other forms of refractive surgery are effective and safe.
