Short-sightedness

About short-sightedness

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). These then pass through your lens, towards your retina at the back of your eye. In a healthy eye, your cornea and lens bend the light to focus it on your retina. Your cornea focuses the light towards your retina and your lens ‘fine tunes’ the focusing of this light.

Having 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. This makes it more difficult for your eyes to focus light directly on your retina. If the light rays aren’t clearly focused on your retina, the objects you see will seem fuzzy or blurred. Close up objects won't look blurry, because the light rays enter your eye at a slight angle. This means they focus on your retina properly.

Short-sightedness is very common and tends to run in families. It usually starts developing between the ages of eight and 12. Because your eyes continue to grow during childhood, short-sightedness usually occurs before the age of 20.

A dioptre (D) is a measurement of the focusing power of a lens. Short-sightedness of up to 3D is termed as mild degree, 3D to 6D is moderate degree and 6D or over is high degree. About one in every 20 children have mild short-sightedness. By adulthood, about one in four adults are short-sighted.

Symptoms of short-sightedness

If you’re short-sighted, you will be able to see close objects clearly, but distant objects will appear fuzzy or blurred. You might find that you narrow your eyes to make far away objects seem clearer.

Young children may not realise they have blurred vision. Signs that your child may be short-sighted include:

  • squinting (narrowing their eyes)
  • frowning
  • sitting close to the TV
  • having trouble seeing the blackboard or whiteboard at school

Other symptoms may include eyestrain and sometimes headaches, but this is uncommon.

If you develop short-sightedness during your childhood or teenage years, you will need to change your glasses or contact lenses often. Short-sightedness will usually stop progressing in your early 20s.

Causes of short-sightedness

There are many reasons why you might develop short-sightedness. Some of these reasons are listed below.

  • If you were born prematurely as a baby, or were underweight at birth, you’re more likely to develop short-sightedness.
  • If your parents are short-sighted, you're more likely to develop short-sightedness.
  • How you use your eyes can affect your sight. Children and young adults who read a lot or do lots of close-up work, for example, using a computer or sewing, may be more likely to develop short-sightedness.
  • Some eye conditions can cause short-sightedness. If you have a hazy cornea (corneal dystrophy) or hazy lens (cataract), not all light can enter your eye, causing your vision to be blurred. This may cause your eye to grow bigger and longer than usual, which leads to short-sightedness.

Diagnosis of short-sightedness

If you're straining to see things in the distance, you should book an appointment with 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 letters 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 glaucoma (an eye condition caused by a build-up of pressure in the eye), diabetes or high blood pressure. Having an eye examination is an important part of looking after your health. You should have an eye examination every two years, even if you have no problems with your vision.

You may need to have eye examinations more often as you get older or if you have a:

  • condition that may affect your sight, such as diabetes or glaucoma
  • close relative who has a condition that may affect his or her sight, such as diabetes or glaucoma

See your optometrist if you’re concerned about your vision or your existing eye condition seems to have changed.

Eye examinations are usually quick and painless, and for some people, they are free. Ask your optometrist or GP for more advice.

Treatment of short-sightedness

Glasses and contact lenses

Short-sightedness can usually be corrected by wearing glasses or contact lenses.

Concave lenses – in a pair of glasses or contact lenses – help focus light more precisely on your retina. If you're mildly short-sighted, you may only need to wear glasses or contact lenses occasionally, such as when you're driving or watching TV.

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 need to be maintained in a particular way. A popular type of contact lens is daily disposables 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. Your optometrist will discuss with you what options are available.

Surgery

Laser refractive surgery
Laser refractive 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.

There are various types of laser refractive surgery, which differ according to how your surgeon gains access to your cornea. These include:

  • photorefractive keratectomy (PRK)
  • photo-astigmatic refractive keratectomy (PARK
  • laser-assisted in situ keratomileusis (LASIK)

Laser eye surgery works very well for most people. However, there is a chance you may not experience the improvement in your eyesight that you expected and need further treatment.

There are some risks associated with laser refractive surgery, including infection of your cornea, symptoms of a dry eye, distorted vision 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.

Laser refractive surgery isn't suitable for everyone and you will need to talk to an ophthalmic surgeon to find out if it's right for you. It may be helpful to write down a list of questions or enquiries to take with you to your first assessment.

Intraocular lens insertion
Lens implants, which are now frequently used, can be categorised into two main types. There are those where the natural lens of your eye is retained. This is often referred to as a ‘Phakic’ contact lens implant or implantable contact lenses (ICL's). There are also those where the natural lens of your eye is replaced.

If you’re severely short-sighted, some types of laser refractive surgery (such as LASIK) may not be suitable. Phakic ICL's may be a better option for you to try. Laser surgery is also permanent and can’t be reversed, but it’s possible to remove or replace a Phakic ICL.

There are some risks and complications associated with intraocular lens replacement. Your ophthalmic surgeon will usually only suggest it if you’re severely short-sighted or unable to wear glasses or contact lenses, for example, if you have a disability.

Radial keratotomy
In this operation, several tiny cuts are made in your cornea to flatten it. This changes your cornea’s focusing power, so that light rays fall more precisely on your retina. This is an older treatment and it has largely been replaced by laser surgery.

Intracorneal rings
Another procedure for the correction of short-sightedness is the insertion of intracorneal rings. The rings are designed to flatten your cornea. Your surgeon will make a small cut in your cornea to fit the ring. This is still a relatively new procedure and complications are still not yet fully understood.

Can children have laser eye surgery to correct short-sightedness?

Answer

No, laser eye surgery isn't suitable for children.

Explanation

Laser eye surgery can be used to correct short-sightedness. However, it's not suitable if you’re under 21. This is because the eyesight of children and teenagers is constantly changing – they may become more short-sighted as they get older. If you decide to have laser surgery for your short-sightedness, your eyesight prescription (refraction) must have been stable for two to three years.

I think I’m short-sighted. Will I have to pay for an eye test?

Answer

More than 30 million people in the UK are entitled to a free eye examination paid for by the National Health Service (NHS). However, if you aren't one of these people, you will have to pay for your eye test.

Explanation

Certain people are entitled to a free eye test. You may be entitled to this if you:

  • are aged 60 or over
  • are under 16
  • are under 19 and in full-time education
  • live in Scotland
  • have diabetes or glaucoma
  • are registered as blind or partially sighted
  • or your partner receive income support, income-based jobseeker's allowance or pension credit guarantee credit
  • have a medical condition and a valid NHS medical exemption certificate
  • are a war pensioner and the prescription is for your accepted disablement – you must have a valid war pension exemption certificate
  • are entitled to vouchers for complex lenses
  • are aged 40 or over and have a close relative with glaucoma

If you think you qualify for a free eye test, speak to your optometrist (a registered health professional who examines eyes, tests sight and dispenses glasses and contact lenses) for advice before you have your eyes tested.

If you don't qualify for a free eye test, you will usually need to pay between £20 and £40 for a 20 to 30-minute appointment. Ask your local optometrist how much they charge for an eye test. There may be extra charges for additional tests.

If your GP has referred you to hospital for an eye test, this will be free.

Are there any risks of wearing contact lenses?

Answer

The main risk with wearing contact lenses is getting an eye infection, but this can be prevented if you look after your contact lenses and your eyes properly.

Explanation

There are many different types of contact lens available. Some you use daily and then throw away, others you clean each night and reuse. It's important to have regular check-ups with your optometrist to make sure that your eyes are healthy and that you're using the best lenses for your needs. Contact lenses are always improving, so even if you haven’t got on with them in the past, it may be worth trying again.

Wearing contact lenses is usually safe and trouble free. However, studies have shown that they slightly increase your risk of an eye infection when compared to not wearing lenses. It's important that you care for your lenses and store them properly to prevent infection. You can help reduce your risk of getting an eye infection by:

  • disinfecting reusable lenses in between using them – this usually means soaking them in a special solution overnight
  • never using the same disinfecting solution twice
  • rinsing your storage case and leaving it open to dry every day
  • using a new storage case every month
  • cleaning your storage case once a week using a clean toothbrush and contact lens solution
  • always washing your hands before you touch your lenses
  • seeing your GP or optometrist immediately if you have red or sore eyes and you think you might have an infection

If you wear contact lenses, you should never:

  • go to bed with a painful red eye – seek medical advice as soon as possible
  • wear your lenses overnight (unless they are specifically designed for this purpose)
  • let tap water come into contact with your lenses
  • wet your lenses with your saliva
  • wear your lenses for swimming (unless you wear goggles)

It’s a good idea to have an up-to-date pair of glasses handy for when you need to remove your lenses. Always seek professional advice if you're having problems with your contact lenses.