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Astigmatism

What is astigmatism?

Astigmatism is a vision condition in which light entering the eye is unable to be brought to a single focus on the retina, resulting in vision being blurred at both far away and near. This is usually due to a small variation or disturbance in the shape of your cornea or the lens inside of your eye. Astigmatism is not a disease, nor does it mean that you have "bad eyes." 

Astigmatism is one of a group of eye conditions known as refractive errors. Refractive errors cause a disturbance in the way that light rays are focused within the eye. With astigmatism, light rays are focused in such a way that both nearby and faraway objects may appear blurry. Astigmatism often occurs with nearsightedness or farsightedness. 


What are the symptoms of astigmatism?

If you experience a distortion or blurring of images at both far away and near, you may have astigmatism. Even if your vision is fairly sharp, headaches, tired eyes, squinting, and eye discomfort or irritation may also indicate a slight degree of astigmatism.
 

What causes astigmatism?
Normally the cornea, the front window of the eye, is smooth (like a baseball) and equally curved in all directions. This causes light entering the eye to be focused equally on the retina. In astigmatism, the front surface of the cornea is curved more in one direction than in the other (like an American football or rugby ball). With the cornea being irregularly shaped, the light hitting the most and least curved surfaces comes to a focus on different parts of the retina. We interpret this as a blurred image. 

Who develops astigmatism?
Astigmatism is very common. Not all corneas are perfectly curved, just as sets of teeth are seldom perfectly aligned. Some experts believe that almost everyone has some degree of astigmatism, often from birth, which may remain the same throughout life.

 

The exact reason for differences in corneal shape remains unknown, but the tendency to develop astigmatism does run in families. For that reason, some people are more prone to develop astigmatism than others.

The degree of variation determines whether or not you will need a correction for the astigmatism. Usually only individuals with moderate to highly astigmatic eyes need corrective lenses or other treatment.

How is astigmatism diagnosed?
Astigmatism is diagnosed in the course of a thorough eye examination by our optometrists. 

Keep in mind that in children, astigmatism is often not detected during routine eye screenings in school. For this reason, children should be examined by our optometrists yearly.

How is astigmatism treated?
If the degree of astigmatism is slight and no other refractive problems like nearsightedness or farsightedness are present, corrective lenses may not be needed. If the degree of astigmatism is great enough to cause eyestrain, headache, or distortion of vision, prescription lenses will be needed for clear and comfortable vision.

The corrective lenses needed when astigmatism is present are called "toric" lenses and have an additional power element called a cylinder. They have greater light-bending power in one axis or direction than in the others. Precise tests will be made during your eye examination to determine the ideal lens prescription.

Today, contact lenses are also a great option for the majority of those patients with astigmatism. Both hard and soft contact lenses work well. Those that have been told that they could not wear contact lenses in the past due to astigmatism are finding it easier to wear lenses and be happy with clear, comfortable vision.

LASIK and other refractive surgeries may also be a great option.

Since there are so many options, our optometrists will help you decide which one of these procedures is best for you.

What is the prognosis with astigmatism?

Astigmatism may increase slowly over time. Yearly eye examinations by our optometrists can help to ensure that proper vision is maintained.