Astigmatism vs short-sightedness (myopia): how the two eye conditions differ

Both conditions are refractive errors, meaning the eye does not bend light to a single sharp point on the retina. They differ in how the focusing goes wrong. In short-sightedness (myopia), light from distant objects is focused in the wrong place, so far-away things look blurry while near objects are clearer. In astigmatism, the cornea or lens has an uneven curve, described by the NHS as like a rugby ball rather than a football, so light is focused at more than one place in the eye.

The result is that short-sightedness is mainly a problem with distance, while astigmatism blurs or distorts vision at any distance. Because astigmatism normally occurs together with short-sightedness or long-sightedness, many glasses prescriptions correct both. If you have been told you have both, it does not mean there are two different diseases to treat: one pair of lenses usually handles them together.

The table below uses the NHS pages for each condition. Individual experience varies, and only an eye test can tell you which you have.

Headaches and eye strain turn up on both lists. In the NHS description, short-sightedness also brings squinting, rubbing the eyes and holding screens close, while astigmatism brings blurred vision and eye strain, particularly after long spells of screen work. A child who struggles to see the board may be short-sighted, astigmatic or both, and a person with undiagnosed astigmatism may well assume they are simply tired.

Because of this overlap, symptoms alone cannot separate the two. The NHS describes an eye test as the way to find out: an optometrist asks you to look at a light or read letters on a chart while different lenses are placed in front of your eyes, and may use drops to see the back of the eye more clearly. If you need glasses, you are given a prescription which you can take to any optician.

It is also the reason children should be tested rather than waiting for them to complain. The NHS says that astigmatism may affect a child's reading or concentration, and that short-sightedness is commonly first noticed in the school years.

For short-sightedness the NHS says glasses or contact lenses help the eyes focus correctly so distant objects are clearer; glasses suit children and adults, contact lenses suit adults and some children. For astigmatism it lists the same options, noting that glasses are the cheapest option and may be free or discounted on the NHS, contact lenses can be a good choice if you are active but carry a risk of eye infection through poor hygiene, and that astigmatism does not always need treatment.

Laser eye surgery or lens surgery is available for some adults with either condition. The NHS says it is not available on the NHS, can be expensive, carries a risk of complications during or after surgery and may be permanent. It describes lens surgery as replacing the lenses in your eyes with artificial lenses.

There is one important difference in children. The NHS says it is hard to prevent short-sightedness, but spending more time outdoors may help stop it getting worse. An optometrist may discuss specially designed glasses or contact lenses, called myopia management or myopia control, or an overnight lens (orthokeratology), but the NHS says myopia management is not available on the NHS because more research is needed. These options apply to short-sightedness, not to astigmatism.

The NHS says astigmatism in 1 eye may cause lazy eye, where the vision does not develop properly, and that it is important this is spotted early so it can be treated. For short-sightedness it says young children with uncorrected short-sightedness may be more likely to get a squint or a lazy eye.

In adults with severe short-sightedness, the NHS says some people are more likely to develop glaucoma, a detached retina (which needs urgent treatment to prevent losing sight), cataracts and macular degeneration. It also says astigmatism can be linked to keratoconus, which is why regular eye tests are important.

Go to an optician if you or your child has symptoms or has not had an eye test for 2 years. The NHS says eye tests are free for some people, including children under 16, teenagers aged 16 to 18 in full-time education, people aged 60 or over, people diagnosed with diabetes or glaucoma, and people on certain benefits. Some people are entitled to an NHS optical voucher towards the cost of glasses or contact lenses.

The NHS says a detached retina needs urgent treatment to prevent losing your sight, so any sudden change in your vision should be checked promptly rather than left for a routine appointment.