Astigmatism is a condition where the front of the eye is not perfectly round. Many cases are mild and require no treatment, but some cause poor vision. Laser eye surgery can be used to correct astigmatism and improve eyesight.
If the transparent layer of tissue known as the cornea at the front of your eye is not spherical and evenly curved, you have astigmatism. Astigmatic corneas can be rugby-ball shaped – this is called regular astigmatism and is the most common kind. Alternatively you may have a cornea which curves in different directions and has some areas thicker than others – this is called irregular astigmatism and is much rarer.
Usually, astigmatism is present from birth, and is identified during routine eye tests.
If you do not have astigmatism, the lines will appear sharply focused and equally dark in the diagram on the right.