What is astigmatism?
Astigmatism is an eye condition that results in distorted vision. A common visual disorder, it is caused by the irregular shape of the eye affecting the way that light rays are focused. Astigmatism usually exists in combination with some degree of hypermetropia (far sightedness) or myopia (near sightedness).
What causes astigmatism?
Astigmatism is caused by the eye not being regular or spherical in its shape. In a patient with perfect vision, the cornea is a regular sphere, like a football. In a patient with astigmatism, however, the eye is not totally spherical, and is shaped more like a rugby ball or an egg. This means the refractive components of the eye (the parts that focus light) do not allow the light rays to meet in the correct place. The result is blurred or distorted vision, where objects can appear blurred or elongated in a particular direction.
People with astigmatism suffer from blurred vision and/or eye strain, which might be worse for distance, but generally affects all distances. Astigmatism symptoms include noticing that objects appear distorted or stretched.
Patients may try to “screw up” their eyes to try to reduce any aberrations in order to improve vision, but unfortunately without optical correction following a specific astigmatism treatment, there is no way the optical system can compensate for this refractive error.
Who is affected by astigmatism?
Astigmatism affects people of any age. It is common for patients with myopia or hypermetropia to have some degree of astigmatism as well. There is quite a strong hereditary link with this disorder, so if family members have astigmatism you are more likely to have it, too.
How is astigmatism diagnosed?
Astigmatism is usually picked up during a routine eye examination carried out by an optometrist. The tests used to measure astigmatism are the visual acuity test (where the patient is asked to read out a series of letters on a chart) and a Keratometer test, which measures the curves of the cornea to determine the shape of the eye and how it focuses light.
Astigmatism treatment options
- Glasses. Special lenses called cylindrical lenses are prescribed to correct any astigmatism the patient may have in order to improve their vision.
- Contact lenses. Depending on the type of astigmatism, rigid gas permeable (RGP) contact lenses may be recommended over soft contact lenses for astigmatism treatment, since these can be used to correct the shape of the cornea and provide a spherical front surface.
Surgical correction: There are two surgical options for astigmatism treatment: Laser Eye Surgery and less commonly, Clear Lens Extraction. The latter involves the insertion of a special intraocular lens (IOL) that corrects for astigmatism.
As always, when considering surgical options for astigmatism treatment, it is important to discuss your particular condition with your eye surgeon. There are a number of factors to consider when deciding which astigmatism treatment path is best for you, including your age, any other eye conditions, the thickness of your corneas and the degree of astigmatism that you suffer from. Your surgeon will be able to explain your treatment options and answer any questions you may have about the procedure.
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