Astigmatism is refractive error which causes light not focus at one point on the retina. This is caused by the difference in power on different meridians. Usually people with astigmatism will have a corneal surface which is shaped more like an oval, this is also known as a toric surface. If you have astigmatism may notice that things in the distance and near may be blurry. You may also experience symptoms of eyestrain, headaches, tired sore eyes and glare at night. The severity of these symptoms may vary depending on the amount of astigmatism you have. You can see this on your prescription by looking at the Cylinder (Cyl). Astigmatism also has an axis which is measured in degrees and it indicates the meridian which has the most minus power. The following is an example of a prescription which contains astigmatism:
+0.25 / -1.25 x 180
The first number +0.25 is the Power or Sphere and indicates how long or short-sighted a person is. The -1.25 is the amount of astigmatism and is sometimes referred to as the Cyl and the 180 is the direction of the Cyl measured in degrees.
Contact lenses can be made to correct astigmatism and there are many manufacturers which have specialised designs to help keep the lenses stable. This is important because astigmatism has direction, which means that the contact lenses must sit in a particular orientation in order to properly correct the astigmatism. These contact lenses are also sometimes known as Toric contact lenses and there are numerous designs to keep the lenses stabilised whilst wearing. Some examples of contact lenses for astigmatism are: