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Astigmatism


What is Astigmatism?

Astigmatism is a refractive error caused by irregular curvature of cornea. It is not an eye disease or eye health problem; it's simply a problem with how the eye focuses light.

An irregularly shaped cornea or lens prevents light from focusing properly on the retina. Most people probably are born with some degree of astigmatism. It frequently occurs with other vision conditions like nearsightedness (myopia) or farsightedness (hyperopia). Slight astigmatism usually doesn't affect vision or require treatment.

The specific cause of astigmatism is unknown. It can be hereditary and is usually present from birth. It can decrease or increase over a period of time.

Most common signs and symptoms of Astigmatism are:

  • Headaches
  • Eyestrain
  • Frequent squinting
  • Difficulty in driving at night
  • Objects both near and far appear blurred

What Causes Astigmatism?

Astigmatism is one type of refractive error, with blurred or distorted vision at near and far distances. Astigmatism is very common, in most cases, is usually present from birth. The reason for the irregular shape of cornea is unknown, but the likelihood of developing astigmatism is inherited.

The cornea of a normal eye is curved like a basketball, with the same degree of roundness in all areas. An eye with astigmatism has a cornea that is curved more like an American football, with some areas that are steeper or more rounded than others. This causes image to appear blurry and stretched out.

In some cases, astigmatism is caused by the shape of the lens inside the eye. This is called lenticular astigmatism, to differentiate it from the common corneal astigmatism. Sometimes astigmatism may also develop following an eye injury or eye surgery.

How is Astigmatism diagnosed?

Your doctor can diagnose an astigmatism through a comprehensive eye examination. This test includes measurement of visual acuity, in which you will be asked to read letters on a distance chart placed 20 feet away from you which is a standard distance for testing.

The curvature of your cornea will be measured with a keratometer. By focusing a circle of light on the cornea and measuring its reflection, it is possible to determine the exact curvature of that area of the cornea's surface. This measurement is necessary in determining the proper fit for contact lenses.

Your doctor will also use a phoropter, an instrument that the measures the amount of refractive error you have and helps determine the power of any optical lenses needed to correct the vision.

Treatment for Astigmatism:

If you have an astigmatism, you have a wide range of options to regain clear vision. You can select the treatment that best meets your visual and lifestyle needs. The options includes:

  • Eyeglasses are the simplest and safest way to correct astigmatism. Your eye care professional will prescribe appropriate lenses to help you see as clearly as possible.

  • Some people will have better vision with Contact lenses rather than eyeglasses. Contact lenses may provide clearer vision and a wider field of view. They are a safe and effective option if fitted and used properly with reglar cleaning. However, contact lenses are not right for everyone.

  • Orthokeratology is a process that uses customized shaping lenses to reshape the cornea. People with moderate astigmatism can wear these contact lenses overnight and then remove them in morning. This gives clear vision without lenses for most of their daily activities but temporarily. If patients stop wearing the retainer lenses, their vision may return to its original condition.

  • Refractive Surgery aims to change the shape of the cornea permanently by removing small pieces of tissue from the cornea. While PRK surgery removes tissue from the superficial and inner layers of the cornea, LASIK removes tissue only from the inner layer of the cornea.