Short-sightedness

Published by Bupa's Health Information Team, June 2010.

This factsheet is for people who are short-sighted, or who would like information about it.

Short-sightedness is a vision problem which means that people can't focus on distant objects, making them look blurred.

The medical term for short-sightedness is myopia. Another name for it is near-sightedness.

About short-sightedness

Normal vision

When you look at something, light rays from the object pass into your eye through your cornea (the clear structure at the front of your eye) then through the lens and on towards the retina at the back of your eye. In a healthy eye the lens and cornea focus the light rays on a small area of your retina so that you can see the object clearly.

What is short-sightedness?

Short-sightedness means you can't focus on distant objects. This may be because your cornea is too curved or your eyeball is too long, meaning that light rays from distant objects focus in front of your retina. This makes distant objects seem fuzzy or blurred.

Close up objects won't look fuzzy, because the light rays enter your eye at a slight angle. This means they focus on your retina properly.

The diagrams below show normal vision and short-sightedness.

Short-sightedness usually starts in children or young teenagers. It's very common and tends to run in families.

Symptoms of short-sightedness

Short-sightedness causes distant objects to appear blurry and unfocused, whereas close objects stay in focus.

Young children may not realise they have blurred vision. If your child frowns, squints a lot or has trouble seeing the TV, he or she may have short-sightedness.

Causes of short-sightedness

There are a number of factors that can contribute to short-sightedness.

If your parents are short-sighted, you're more likely to develop short-sightedness. If one of your parents is short-sighted, there is a one in three chance you will also be short-sighted. If both your parents are short-sighted, there is a one in two chance you will be too.

Babies who are born earlier than usual and who are underweight at birth are more likely to develop short-sightedness.

Researchers have found that the number of people who are short-sighted differs depending on ethnic background. For example, around eight in every 10 people of Asian origin are short-sighted, whereas only three in every 10 people of European origin are.

There is also increasing evidence to show that how you use your eyes when you're a child and young adult can affect your sight in the future. Children and young adults who read a lot or do a lot of close-up work, for example using a computer, may be more likely to develop short-sightedness. Research also shows that people who have jobs that require them to read a lot, for example lawyers and doctors, are more likely to be short-sighted. The reasons behind this aren't fully understood.

Diagnosis of short-sightedness

If you're straining to see things in the distance, you should visit an optometrist (a registered health professional who examines eyes, tests sight and dispenses glasses and contact lenses) to have your eyes tested.

In order to diagnose short-sightedness, your optometrist will usually ask you to read a standard chart (called a Snellen chart) from a distance of six metres. The chart has large letters at the top and small ones at the bottom.

It's important to have regular eye tests. As well as diagnosing any vision problems, they can reveal other serious illnesses, such as diabetes or high blood pressure. According to the College of Optometrists, you should have an eye test every two years. Depending on your age, and if you have any known sight problems or illnesses that affect your vision, you may need to have more regular eye tests. Ask your optometrist or GP for more advice.

Treatment of short-sightedness

Glasses and contact lenses

Short-sightedness can usually be corrected by you wearing glasses or contact lenses. Your optometrist will discuss with you what options are available.

If you're mildly short-sighted, you may only need to wear glasses or contact lenses occasionally, such as when you're driving.

Contact lenses tend to be more expensive than glasses, and you need to be comfortable touching your eyes to use them. You will need to keep them clean and some types require a lot of care. A popular type of contact lenses is daily disposable lenses, which you wear for one day and then throw away. You don't need to clean or store these lenses.

Glasses are usually recommended for children. They may also be more suitable than contact lenses for older people.

Surgery

Laser refractive surgery
Laser surgery involves small alterations being made to your cornea using a laser, so that light rays are correctly focused onto your retina. To treat short-sightedness, the centre of your cornea is made flatter by removing more tissue from the centre than from the edge.

The procedure is carried out under local anaesthesia, so you're awake throughout. It only takes a few minutes. The procedure works very well for most people. However, you should be aware that you may not experience the improvement in your eyesight that you expect and you may need further treatment.

There are some risks associated with laser refractive surgery, including infection of your cornea and problems with the flap that is made in your cornea during certain types of laser eye surgery.

If you choose to have laser refractive surgery, it's important that you consider the benefits and risks of the operation before you go ahead. You should also make sure that it's carried out by a trained professional.

Intraocular lens insertion
In this operation, a surgeon inserts an artificial lens in front of your own lens. You will be given a local anaesthetic beforehand. The artificial lens allows light rays to focus on your retina rather than in front of it.

This is a new type of treatment and not much is known about the long-term side-effects. It's not always available and your surgeon will usually only suggest it if you have severe short-sightedness or are unable to wear glasses, for example if you have a disability.

Radial keratotomy
In this operation, several tiny cuts are made in your cornea to flatten it. This is an older treatment and it has largely been replaced by laser-based procedures.

For answers to frequently asked questions on this topic, see Common questions.

For sources and links to further information, see Resources.