Lenticular astigmatism is rarer and caused by an irregularly shaped lens. Corneal astigmatism is much more common and caused by an irregularly shaped cornea. The cornea is normally symmetrical and round, but in astigmatism the cornea can become elongated like a football. This causes the light rays to split in the eye, never achieving a singular point of focus.
Why some people are born with an elongated cornea is unknown. Some studies show that it could be hereditary. Astigmatism is prevalent in premature babies and babies born at a low body weight.
Astigmatism can be caused by injury to the eye and subsequent scarring of the cornea. Some surgeries that can scar the cornea may also cause astigmatism. Keratoconus, a disease of the eye that causes a thinning of the cornea to occur, can cause astigmatism by changing the shape of the cornea.
Onset and Treatment
Treatment options for astigmatism include eyeglasses or contact lenses. Orthokeratology is another treatment that involves wearing special contact lenses that gradually reshape the cornea into its proper dimensions.
Advanced treatments for astigmatism include:
• Laser eye surgery: A surgical procedure where vision is corrected by removing a small part of the eye with a laser. Using a highly focused laser beam, a specialist reshapes the cornea, flattening the cornea and correcting the focus.
A diagnosis of astigmatism can be made during the course of a comprehensive eye exam. A phoropter allows the doctor to show a series of lenses to a patient, switching back and forth between them to determine the best fit for corrective lenses.
A keratometer, a device to measure the curvature of the cornea, may be used as well. Corneal topography is a technologically advanced treatment where computer imaging is used to make a map of the cornea. This map provides the most complete view of the cornea and is used when diagnosing astigmatism, as well as being used to fit contacts to the eye and prepare patients for eye surgery.
There is no known way to prevent astigmatism. Maintaining overall health as a means to eye health is always recommended. Fruits and vegetables high in vitamins A, C and E are key foods for eye health.
Taking frequent breaks while doing close work allows the ocular muscles to unwind and can help ward off eye strain. Try looking off into the distance every ten minutes or so to keep your eyes relaxed. Wearing sunglasses to prevent UV damage to the eyes helps keep vision sharp later in life.
When to see an eye care professional
If you are experiencing headaches, fatigue, eye strain or blurred vision, you may have astigmatism and should be examined by an optometrist or ophthalmologist.
Always see an eye care professional immediately if you have any sudden changes in vision. This includes darkening around the edges of your vision, dark spots in front of your eyes, halos around bright lights, a loss of vision in one part of your field of sight or any other noticeable change.