What is Astigmatism?

Many people have never heard of astigmatism, although it is an extremely common eye condition.

Astigmatism is one type of refractive error. Nearsightedness and farsightedness are other types of refractive error. Refractive errors are not eye diseases. Refractive error is a result of and imperfection of the size and shape of the eye, which results in blurry or double vision.

Causes of Astigmatism

Astigmatism is generally caused by a cornea with an irregular shape.  With astigmatism, the cornea is not round and spherical and is instead irregular having two curves instead of one curve. Astigmatism in some cases can also be caused by a lens, located inside the eye, that is non-spherical in shape.

Eyes with astigmatism distort the light that comes into the eyes because the cornea is not spherically shaped. This causes the light rays entering the eye to create two images in the back of the eye (because of the two curves), instead of one image. This is what causes the distortion in sight.

A normal cornea’s shape should be like that of a baseball. The cornea is the front, clear layer of the eye. A person with astigmatism has a cornea that is shaped more Toric, similar to a football. Because the cornea is toric, light bends to focus on a line instead of a point as it enters the eye, causing vision distortion or blurriness. Some people with astigmatism might squint frequently in an effort to see clearly because astigmatism can make it hard to focus on fine details or objects. Squinting too much can cause headaches due to the strain from trying to focus.

Symptoms of Astigmatism

Small amounts of astigmatism can go unnoticed, however, those with significant astigmatism may experience eye fatigue, eyestrain, and headaches.

Astigmatism is a condition that usually develops in  early childhood. According to a study from The Ohio State University School of Optometry, 28% of school age children suffer from astigmatism. Parents should know that their children might not be aware that their vision is blurry, as they lack a reference of experience regarding what is clear vision. Nevertheless, astigmatism should be treated because vision problems can lead to learning problems and difficulty with extracurricular activities.Children should have their eyes examined at an eye doctor’s office at least once a year, and especially before starting school.

Regular vs. Irregular Astigmatism

Regular astigmatism, the most common type of this condition, is found in almost half of the adult population. Irregular astigmatism is less common and can be caused by eye disease, surgery or injury. The most common cause of irregular astigmatism is a disease called keratoconus, which gradually thins the cornea, typically in the second decade of life. Irregular astigmatism can be difficult to treat with eye glasses. Custom contacts may be useful depending on the severity of irregular astigmatism.

Can Laser Eye Surgery Treat Astigmatism?

Astigmatism can be fully corrected using prescription glasses or contact lenses. Soft contact lenses are the most common option, but do not provide the best vision as they do not treat the astigmatism and only mask it. RIgid gas permeable (RGP or GP) are a better choice as they actually change the shape of the cornea while they are being worn. Rigid gas permeable lenses usually give the clearest vision but the adaptation process will be significantly longer.

Another option are hybrid contact lenses. These contacts have a center made from a rigid gas permeable (RGP) lens and an outer ring made of soft contact lens material. This type of lens provides both excellent clarity and comfort. 

Depending on the type and severity of astigmatism, the condition can often be treated with laser eye surgery. Laser-assisted in situ keratomileusis (LASIK) is a type of laser eye surgery that reshapes the inner layer of the cornea to correct astigmatism. It is important to determine which type of astigmatism you have in order to determine which eye treatment option is best for you.

LASIK eye surgery has proven an effective treatment for people with mild or moderate astigmatism. LASIK is also a convenient option for physically active people who find eye glasses or contacts a nuisance, even if they don’t have astigmatism.