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The simple answer to “what is astigmatism” is it’s changes in the eye that distort vision. It is one of the most common abnormalities, called refractive errors, that affect the way the eye bends, or refracts, light to form images on the retina. As a result of astigmatism, objects you look at may seem blurry, fuzzy, or distorted. You can have astigmatism at the same time as nearsightedness or farsightedness.
Astigmatism is usually caused by a misshapen cornea (corneal astigmatism). In some cases, the problem may lie in the lens (lenticular astigmatism). Normally, the curve of the cornea is roughly spherical, like a basketball. But in astigmatism, the cornea is irregularly shaped—more oblong than spherical. This causes light to focus unevenly on the retina, blurring and stretching out (distorting) images. As a result, vision is blurry at all distances, near and far. Astigmatism often accompanies nearsightedness or farsightedness. Scarring or thinning of the cornea can lead to what is astigmatism.
Who Gets Astigmatism?
Many people are born with astigmatism, possibly because of an inherited genetic predisposition. Others develop it later, whether from the aging of the eye, an injury, scarring or thinning of the cornea, or as a complication of cataract surgery. About half of people 60 and older have astigmatism.
What Are the Symptoms?
The main thing people notice is that vision is blurred or distorted at near and far distances. But astigmatism can also cause eyestrain, eye irritation, or headaches. You may squint more often, or have more trouble driving at night.
Astigmatism can be diagnosed during a comprehensive eye exam. The doctor will test your visual acuity, which is the ability to see letters on a chart at a distance. You’ll also undergo a test in which you look through a variety of different lenses to see which one corrects your vision best, which also determines the degree of astigmatism you have in one or both of your eyes.
How is Astigmatism Corrected?
Glasses or contacts are the simplest and least expensive way to correct astigmatism. The lenses are shaped to compensate for the astigmatism in your natural eyes. For some people, the preferred option might be refractive surgery, such as laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), or radial keratotomy (RK). This reshapes the cornea to correct the astigmatism.
Another option is orthokeratology, also known as Ortho-K therapy or corneal reshaping. Approved for both adults and children, the therapy involves wearing special rigid contact lenses at night that temporarily reshape the curvature of the cornea. Ortho-K can correct myopia and astigmatism within a certain range of severity. Orthokeratology does carry risks of corneal damage or infection, so discuss this with your doctor.