Astigmatism is caused by distortion in the shape of the cornea. It is a refractive error characterized by an alteration in the curvature of the cornea, due to which the light is not able to focus on the retina. This causes distorted or blurred vision. Astigmatism can either congenital or acquired. It is usually associated with myopia or hypermetropia.
Signs and symptoms
Following signs can be noticed if you have astigmatism.
Strain in the eyes
Blurred or distorted vision
Types of astigmatism
Myopic astigmatism - When one of both principal meridians of the eye is nearsighted.
Hyperopic astigmatism - When one or both principal meridians are farsighted.
Mixed astigmatism - When one of the principal meridians is nearsighted and the other is farsighted.
The prime feature of astigmatism is distortion in the curvature of the eye. This is congenital in most of the cases. However, in some cases, this can happen after an injury or surgery, or any eye related disorder.
How is it diagnosed?
The condition of astigmatism is diagnosed through an eye exam. There are a series of tests to examine and analyze the ophthalmic health and refraction. This determines the way in which the light bends in the eye. Different instruments are used to enable the light to get focussed directly at the eyes.
Most of the top ophthalmologists in India prefer to do a test called Manual refraction. An instrument known as phoropter is placed in front of the eyes. This instrument contains several lenses that are placed in front of the one by one to make the comparison.
How is it treated?
Two types of approaches are used for the treatment:
Eyeglasses - These are made with lenses to compensate for the distorted shape of the eye. The eyeglass lenses are able to make the light bend on the retinal at a proper position. The eyeglasses are also used for the correction of other refractive errors like nearsightedness or farsightedness.
Contact lenses - These are similar to the eyeglasses. These have the ability to correct astigmatism. These may be disposable soft, extended wear, rigid, gas permeable or bifocal. However, wearing contact lenses for an extended period of time can lead to increased risk of infection.
This is done to improve the vision and reduce the need for eyeglasses or contact lenses. A laser beam is used to reshape the curves of the cornea. Following are the types of refractive surgery, which are most commonly done by the doctors. These include:
Laser-assisted in-situ keratomileusis (LASIK) - A thin flap is made in the cornea and makes the shape correction by using a laser machine. After the completion, the flap is repositioned.
Laser-assisted subepithelial keratectomy (LASEK) - In this type of procedure, the protective cover is loosened with the help of a special type of alcohol. Then, the curvature of the distorted cornea is changed followed by repositioning of the loosened epithelium.
Photorefractive Keratectomy (PRK) - This is another procedure similar to LASEK. However, this involves the removal of the epithelium. After completion of the surgery, it grows back naturally by adapting to the new shape of the cornea.
Epi-LASIK - Here, a special mechanized blunt blade is used to isolate a thin sheet of the epithelium. Then an excimer laser is used to reshape the cornea and reposition the epithelium.
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