If your eye is shaped more like a rugby ball than a football, light rays are focused on more than one place in the eye, so you don’t have one clear image. This may make it hard to tell ‘N’ from ‘H’, for instance.

Glasses which correct this may feel strange at first, although vision with the glasses will be clear. Astigmatism often happens alongside either long- or short-sighted and glasses are used to make the focus clear.