It occurs when the cornea or lens isn’t a perfectly curved shape. Many people who wear glasses have some degree of astigmatism.

Astigmatism belongs to a group of related eye conditions known as refractive errors. Other common refractive errors include:

• short-sightedness (myopia)
• long-sightedness (hypermetropia)

If you have astigmatism, it’s likely you’ll also have one of these conditions.

Left untreated, astigmatism can cause headaches, eye strain and fatigue (tiredness), particularly after doing tasks that involve focusing on something for long periods, such as reading or using a computer. – source: NHS