Astigmatism (focusing error)
Astigmatism is caused by an irregular shaped cornea (clear dome shaped window covering the eye). In a normal eye the cornea is sphere shaped, like a basketball, but in an eye with astigmatism, the cornea can be shaped like a rugby ball. Astigmatism can sometimes be caused by the lens inside the eye being tilted.
People with astigmatism usually have problems maintaining focus on an object, whether it is up close or far away. Instead of an image being focused onto one point of the retina, it is focussed on more than one point of the retina. This results in a blurry image. Astigmatism can also result in tired or fatigued eyes.
Some people can have astigmatism by itself and others can have a combination of astigmatism, hyperopia and/or myopia, or presbyopia.
Astigmatism can be corrected with spectacles or contact lenses.