Astigmatism – Symptoms, Causes, Types, Test, Treatment

By | July 6, 2015

What is Astigmatism?

Astigmatism is defined as mild imperfection of the eye that causes blurred vision. Actually there will be some degree of astigmatism in each person and occurs due to difference in the curvature of the eye. The surface of the cornea may have slightly different curvature due to astigmatism. Normally the surface of the cornea or the lens will be steeper in all directions but people with astigmatism may have slightly raised curvature in one direction causing blurred vision. It can be easily treated using eyeglasses or contact lenses. Astigmatism often occurs in combination with myopia (nearsightedness) or hyperopia (farsightedness).

Symptoms :

Astigmatism can cause blurry vision and eyestrain. For some people distant objects may not look clear and for others nearby objects will look blurred. It can also cause headaches for some people due to eyestrain. It is good to go for eye exam if you are above 40 years even if you don’t have any health issues. Your ophthalmologist can easily detect the problem and prescribe suitable corrective glasses. For people with diabetes you need to check your eyes more frequently than others.

Causes :

Astigmatism is not a disease and occurs due to slight difference in curvature of the corneal surface. But what exactly causes this difference in some people is not known.

Anatomy of the Eye :

Normally the surface of the cornea and the lens will be perfectly smooth. But for some people there will be slight difference or bends in the curvature of the cornea which in turn focuses the light unevenly causing refractive error. Such people can see only part of the object due to error in refraction which gives the shape of distorted image of the object. This causes blurry vision or wavy vision. A person is said to have lenticular astigmatism if his lens is not smoothly shaped and corneal astigmatism if his cornea takes a distorted shape instead of flat smooth one.

Types :

Astigmatism is of two types namely myopia (causing nearsightedness where the light gets focused in front of the retina) and farsightedness or hyperopia that is caused when the curvature of the cornea is too little when compared with your eye. Here the image of the object is focused at the back of your eye and hence you may not be able to see nearby things properly. Astigmatism can be caused due to extensive reading or reading in dim light for extended period or by watching television too close. For some people it is inherited and present from birth.


Diagnosis :

After listening to your symptoms, your doctor may do routine eye exam to detect the extent of astigmatism. He/she may ask you to read out letters or numbers placed on a chart at some distance. She may also use keratometer to determine the extent of curvature of the cornea or lens. Computer aided corneal mapping is also done by some doctors. Retinoscopy is also done to find out how the light is focused by your eyes.

Treatment :

Your ophthalmologist will be able to prescribe suitable corrective lenses or eyeglasses after completing the testing. She will be able to detect the extent of curvature while testing procedure. Corrective eyeglasses are often prescribed to make good the uneven shape of the curvature of the cornea or lens. It is effective in repairing the refractive errors caused by astigmatism. Alternatively contact lenses can also be used for correcting astigmatism. You have wide range of options in contact lenses and you can choose the desired one.

You need to follow the instructions of your ophthalmologist in wearing contact lenses or eyeglasses frequently. If you discontinue using them your eyes might get back to the former shape causing blurred vision again. Remember contact lenses can cause eye infection and hence you need to maintain it properly. They are expensive when compared to eyeglasses. For some people, refractive surgery is done for resizing the eye surface. But not all the people are suitable for this procedure.

LASIK surgery is done in which thin round flap is cut from the cornea and the shape is resized to make it smooth and fully round. The same procedure can be done using PRK in which the surgeon would remove the outer layer of the cornea and reshape it suitably. For people with thin cornea or those who are at risk of getting eye injury can opt for LASEK surgery in which the layer of the cornea is folded making the eye less prone to any injury.

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