Astigmatism is a common, usually minor eye condition that causes blurred or distorted vision.
This condition occurs when the cornea or lens of the eye is not perfectly curved. Many people who wear glasses have some degree of astigmatism.
Astigmatism belongs to a group of eye conditions known as refractive errors. Other refractive errors include:
Nearsightedness (myopia)
Farsightedness (hyperopia)
If you have astigmatism, you are probably also nearsighted. If left untreated, astigmatism can cause headaches and eye strain, especially after doing activities that require you to focus on something for a long time, such as reading or working on a computer.
What causes astigmatism?
Astigmatism is often caused by an irregular shape of the cornea or lens. The cornea is the clear tissue at the front of the eye.
The cornea should normally have a regular curve similar to the surface of a football, but when the eye has astigmatism, the curve is irregular and abnormal, resembling the surface of a rugby ball. This means that light rays entering the eye are not focused properly, creating a blurred image.
In most cases, astigmatism is present from birth. However, it can sometimes develop after an eye injury or as a complication of eye surgery.
Types of astigmatism
There are two types of astigmatism: regular and irregular.
Regular astigmatism is when the curvature of the cornea is more in one direction (axis) than in another. This type of astigmatism is more common than irregular astigmatism and can be corrected with glasses or contact lenses.
Irregular astigmatism occurs when the curvature of the cornea is not the same across the entire surface of the eye. Instead of being more curved in one direction (axis), it can be curved in different directions, or the slope of the cornea is more steep.
Irregular astigmatism often occurs as a result of an eye injury that leaves a scar on the cornea. In this type of astigmatism, vision is not corrected with glasses, but with prescription lenses.
Diagnosing astigmatism
Astigmatism is often diagnosed after a routine eye exam.
It is very important that you and your children have regular eye exams, because astigmatism may not be detected for years, which can affect your and your child's ability to study and concentrate.
Treatment of astigmatism
In many cases, the symptoms of astigmatism are very mild. So no specific treatment is needed to correct vision. However, in cases where vision is significantly affected by astigmatism, glasses or contact lenses can be used to correct vision.
In adults, laser treatment can permanently treat astigmatism. However, it is unlikely that you will be able to get laser treatment covered by the NHS.
In many cases, astigmatism is not severe enough to require treatment.