Astigmatism: what it is, symptoms, causes and treatment

The NHS says astigmatism is a common eye condition that can cause blurry vision. Your eye is shaped more like a rugby ball than a football, so light is focused at more than one place in the eye. Look After Your Eyes, a College of Optometrists-backed information site, says light focuses on more than one area of the retina, so vision is distorted (you may find it difficult to tell N from H, for instance) or blurry.

Moorfields Eye Hospital says that usually the front surface of an eye is rounded like a football, but in an eye with astigmatism it is shaped like an oval rugby ball. This changes the path of light into the eye so the image formed at the back of the eye is not sharply focused. Alongside astigmatism, short or long sightedness are also common.

Look After Your Eyes describes astigmatism as a type of refractive error, like long-sight and short-sight, caused by the shape and size of your eye. It says it is very common and easily corrected with glasses or contact lenses.

The NHS lists the main symptoms as blurred vision, headaches and eye strain, which you may notice after concentrating for a long time, such as when using a computer. Moorfields lists blurring and distortion of near or far-away objects, headaches when trying to focus and tired eyes.

Many people with a small degree of astigmatism have excellent eyesight, according to Moorfields; those with more severe astigmatism may notice the symptoms above. If discomfort or eyesight problems are affecting your enjoyment or ability to do day-to-day activities, Moorfields recommends consulting an optometrist or ophthalmologist.

The NHS says astigmatism does not always need to be treated. When it does, the possible treatments are glasses, contact lenses and laser eye or lens surgery. Look After Your Eyes says that if your astigmatism changes, or you are having it corrected for the first time, your glasses may feel strange at first while your brain gets used to seeing things corrected, but this will settle down.

Moorfields says the exact causes of astigmatism are unknown, although genetics can play a part, and that sometimes astigmatism can develop after an eye injury, surgery or because of an eye disease. It says astigmatism typically develops in early childhood or in your teens.

Moorfields adds that watching television, using a computer or mobile device regularly or reading in bad light does not cause astigmatism.

The NHS says astigmatism can be linked to an eye condition called keratoconus, so it is important to get regular eye tests.

The NHS says astigmatism in one eye may cause lazy eye (amblyopia), where vision does not develop properly, and may also affect a child's reading or concentration. It stresses that it is important this is spotted early so it can be treated. Moorfields says that if high astigmatism develops in early childhood it can cause a lazy eye, and that vision checks performed in children starting reception year at school are designed to pick up short-sightedness, long-sightedness and astigmatism.

The NHS lists signs of lazy eye as shutting 1 eye or squinting, eyes pointing in different directions, tilting the head, tired eyes and rubbing the eyes, headaches, difficulty catching or throwing, and tripping or falling over a lot. It says many children do not notice anything wrong with their vision, and that treatment should ideally start before the age of 7, when vision is still developing. Treatment includes glasses, an eye patch over the stronger eye for a few hours a day for several months, or eye drops that temporarily blur vision in the stronger eye.

The NHS advises going to an optician if you or your child has symptoms of astigmatism or has not had an eye test for 2 years. For a child, the NHS lazy eye page explains that the optometrist will ask you to look at lights or read letters while different lenses are placed in front of your eyes, and may use eye drops so they can see the back of the eye more clearly. If you need glasses you will be given a prescription that you can take to any optician.

The NHS says you are entitled to a free NHS sight test if you are under 16, are 16, 17 or 18 and in full-time education, are 60 or over, have been diagnosed with diabetes or glaucoma, are 40 or over with a close relative with glaucoma, or are on certain benefits such as Universal Credit or Pension Credit Guarantee Credit. Under-16s and some others are also entitled to an optical voucher towards the cost of glasses or contact lenses.

Go to an optician if you or your child have symptoms of astigmatism or have not had an eye test for 2 years, according to the NHS. If you have a sudden change in vision, severe eye pain or a red eye, seek urgent advice from NHS 111, your GP, an optometrist or an eye casualty department, because those are not typical astigmatism symptoms.

Eye tests and glasses are provided by high street opticians, with free NHS sight tests for eligible groups. Look After Your Eyes lets you find a local optometrist. Laser and lens surgery are not available on the NHS, so they are arranged privately.

Before paying for surgery, ask how your astigmatism will be measured, what outcome is realistic, whether you may still need glasses afterwards and what the risks are. Moorfields notes that laser surgery is generally considered once the eye is fully grown.