Astigmatism is a refractive error where cornea is irregularly curved. Instead of being round, it may be shaped more oval. This irregular shape causes light to scatter and to bend, or refract, improperly as it passes through the cornea. Instead of focusing directly on the retina, some light rays focus in front of and some focus behind the retina. These multiple focal points distort vision. In some cases, an irregularly curved lens produces minor degrees of astigmatism.
What is physiological astigmatism?
Everyone has a small degree of astigmatism due to different refractive power of horizontal and vertical meridian of the cornea, but this astigmatism doesn’t cause any vision problems.
Can astigmatism be associated with some other refractive error?
Yes. Since in astigmatism there are two focal lines instead of one focus, it is possible that both lines focus in front of retina (myopic astigmatism), or behind retina (hypermetropic astigmatism).
Focus from one meridian can be on the retina, while other can be in front, or behind retina and it is also possible that light rays focus from one meridian in front of retina and from other meridian behind retina.
What is regular and irregular astigmatism?
When we talk about corneal refraction we mention two main meridians – one vertical and one horizontal. There are many meridians in different angles between these two. If refractive power of these meridians changes gradually from vertical to horizontal we talk about regular astigmatism. Irregular astigmatism doesn’t have gradual changes in refraction between meridians.
What is oblique astigmatism?
It is astigmatism where instead of vertical and horizontal meridian, the most affected meridians are some between vertical and horizontal.
What is the cause of astigmatism?
The main cause is unknown. It is generally considered that irregular shape of cornea is inherited. It can also result from pressure from the eyelids on the cornea, incorrect posture or an increased use of the eyes for close work. Some corneal diseases can leave scars on cornea and create astigmatism.
Astigmatism can be caused also by irregular shape of the lens.
What Are the Symptoms of Astigmatism?
People with undetected astigmatism often experience headaches, fatigue, eyestrain and blurred vision at all distances. While these symptoms may not necessarily be the result of astigmatism, you should schedule an eye exam if you are experiencing one or more symptoms.
How Are Astigmatisms Treated?
Almost all degrees of astigmatism can be corrected with properly prescribed eyeglasses or contact lenses. For a person with only a slight degree of astigmatism, corrective lenses may not be needed at all, as long as other conditions such as nearsightedness or farsightedness are not present. If the astigmatism is moderate to high, however, corrective lenses are probably needed.
Astigmatism can also be treated by refractive surgery. There is also an alternative form of treatment in a form of eye exercises that can reduce astigmatism. For more information about treatment visit this link HERE.
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