Astigmatism
The vision problems caused by astigmatism are a result of defects within the eye.
These defects are usually present from birth.
The eye is made up of three functional components. They are the:
Astigmatism usually occurs as a result of problems with the cornea or lens.
The cornea is a transparent layer of tissue that covers the front of the eye and helps protect the eye from damage. The cornea and lens are also responsible for focusing incoming light on to the retina to create a clear image.
To work properly, the cornea needs to be perfectly curved, like the surface of a football. However, in astigmatism the cornea is shaped irregularly, like the surface of a rugby ball.
When light hits an irregularly curved cornea, it's not focused correctly on to the retina. The incorrect focus blurs the image, resulting in blurred vision.
Astigmatism caused by problems with the cornea is known as corneal astigmatism.
The same problem can also sometimes be caused by an irregular-shaped lens that bends light unevenly in the eye. This is known as lenticular astigmatism.
It's not known why some people are born with astigmatism, but there may be a hereditary element.
Other possible causes of astigmatism include:
Astigmatism is a common and usually minor condition of the eye that causes blurred or distorted vision.
The vision problems caused by astigmatism are a result of defects within the eye. In most cases these defects are present from birth.
Astigmatism is usually diagnosed after a routine eye test.
In many cases, the symptoms of astigmatism are so mild that treatment to correct vision isn't required.