An eye with astigmatism fails to focus light on the retina to produce clear vision. With astigmatism, incoming light focuses on multiple points that can either be in front or behind the retina (or both).
Causes of Astigmatism
Astigmatism is most commonly caused by an irregularly shaped cornea. Instead of being shaped like a baseball, it is shaped more like a football. As a result, one meridian is more curved than the one perpendicular to it.
In an eye with astigmatism, the steepest and flattest meridians are called principal meridians. For a broad understanding of what a meridian is, think of the face of a clock. The line connected the 12 and 6 is one meridian, whilst the line connecting the 3 and 9 is another.
Types of Astigmatism
Astigmatism can vary from three different types. The first type is myopic astigmatism. One or both principal meridians are nearsighted in an eye with myopic astigmatism. The second type is hyperopic astigmatism. In an eye with hyperopic astigmatism, one or both principal meridians are farsighted. The third and final type of astigmatism is mixed astigmatism. It is a combination of both hyperopic and myopic astigmatism with one principal meridian being nearsighted and the other farsighted.
Symptoms of Astigmatism
Astigmatism can cause blurred vision at all distances depending on the type. Uncorrected astigmatism may result in eye strain, headaches, and fatigue after reading or other visual tasks. It is common for someone with astigmatism to find themselves often squinting to bring objects into focus.
Like most refractive errors, astigmatism can be corrected with prescribed lenses or refractive surgery. Almost all cases can be corrected with glasses or contacts.
A special type of soft contact lenses called a toric lens is most commonly prescribed by optometrists to correct astigmatism. They are made to bend light more in one direction than the other to correct astigmatism.
If your degree of astigmatism is more severe, an optometrist may prescribe gas-permeable rigid contact lenses. These lenses are less rigid and optically replace the cornea as a refracting surface. Gas-permeable contact lenses are less common than the use to be, but you can still find a selection at our contact lens dispensary.
If you would prefer not to wear corrective lenses, or your case of astigmatism is too severe for them, refractive surgery is available. Refractive surgery changes the shape of your cornea using a laser. There are multiple types and each procedure should be discussed with the optometrist prior to choosing.