It is thought that the condition is inherited, so you are more likely to be astigmatic if one or both of your parents has the condition. However, it can also occur as a result of an eye injury that causes scarring on the cornea and may also come about due to the eye condition keratoconus.
To understand the condition, it first helps to understand how the eye works.
Astigmatism is a refractive error caused by an imperfection in the eye – usually in the cornea (the clear, front ‘window’ of the eye), but sometimes in the lens. The imperfection changes the way your eye focuses the light rays that pass into it. This can happen when:
- The cornea is an oval ‘rugby ball’ shape rather than a round soccer ball shape.
- The lens is an oval ‘rugby ball shape’ rather than a round ‘soccer ball shape.
When either of these imperfections occurs, it means the light that enters your eye doesn’t have a single point focus. This makes objects at all distances look blurry.
Compare the two images below: