Astigmatism is a common eye problem in which a person’s cornea or lens has an irregular shape. These problems are known as Corneal astigmatism and Lenticular astigmatism respectively.
The cornea is a clear layer that completely covers the part of the eye that has color. Ideally, the shape of the cornea is round, like a tennis ball. The cornea’s job is to bend rays of light that enter the eye so that these light rays can be better focused on the lens enabling the retina to produce a clear image.
When the cornea has a more oval shape, like that of a football, light cannot focus properly. Instead of one focus point, as is what happens when the cornea is properly shaped, the misshapen cornea focuses light onto two areas of the retina. That is what results in blurred vision and/or the appearance of doubled vision.
Symptoms of Astigmatism
Blurred vision, ‘ghosting’ or images that are doubled are the most common symptoms of astigmatism. These types of vision problems occur at all distances. Fatigue, eye strain and frequent headaches are other symptoms that may indicate astigmatism.
Who is at risk?
The shape of the cornea can be affected by anything that causes the eyelids to exert excessive pressure on the cornea. Other risk factors for astigmatism include hereditary, poor posture and performing redundant and excessive amounts of up-close work. Those who are nearsighted or farsighted are also at higher risk of developing astigmatism. Other factors that can increase the appearance of astigmatism include head trauma or a cut, tear or scar on the cornea.
Keratoconus, a condition which over time causes the cornea to thin and take on a more cone shape can also cause astigmatism. This condition develops around puberty and affects more women than men. It’s also caused by excessive rubbing of the eyes.
Finally, diabetics are at increased risk of developing astigmatism as elevated blood-sugar levels can cause the shape of the lens to change.
A routine eye exam is the easiest way to detect astigmatism. The eye doctor will do a number of tests to determine vision clarity. To determine how light rays focus on the retina the eye doctor can perform a refractive evaluation. Reading the eye chart is a good way to determine visual acuity. Checking eye muscle performance, eye coordination and eye focusing capability are also part of a routine eye exam and can all help determine the presence and degree of astigmatism. Astigmatism is measured in terms of diopters and ranges from mild to severe.
Since astigmatism is an eye condition and not an eye disease, it is highly treatable. Common treatment options include corrective eye glasses and (toric) contact lenses.
Surgical treatment options have been highly successful at correcting the shape of the cornea. Photorefractive Keratectomy or PKR uses laser beams to change the cornea’s shape. LASIK surgery involves making small incisions on the sides of cornea using laser beams. With Radical Keratectomy, laser beam incisions are made into the cornea.