Short-sightedness

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Overview

Short-sightedness
Short-sightedness

Short-sightedness, or myopia, is a very common eye condition that causes distant objects to appear blurred, while close objects can be seen clearly.

It's thought to affect up to 1 in 3 people in the UK and is becoming more common.

Short-sightedness can range from mild, where treatment may not be required, to severe, where a person's vision is significantly affected.

In children the condition can start from 6 to 13 years. During the teenage years when the body grows rapidly myopia may become worse. Myopia can occur in adults.

Signs that your child may be short-sighted can include:

  • needing to sit near the front of the class at school because they find it difficult to read the whiteboard
  • sitting close to the TV
  • complaining of headaches or tired eyes
  • regularly rubbing their eyes

Getting your eyes tested

If you think you or your child may be short-sighted, you should book an eye test at a local opticians. . Find an opticians near you.

You should have a routine eye test at least every two years, but you can have a test at any point if you have any concerns about your vision.

An eye test can confirm whether you're short or long-sighted, and you can be given a prescription for glasses or contact lenses to correct your vision.

For some people - such as children under 16, or those under 19 and in full-time education - eye tests are available free of charge on the NHS.

What causes short-sightedness?

Short-sightedness usually occurs when the eyes grow slightly too long.

This means that light doesn't focus on the light-sensitive tissue (retina) at the back of the eye properly.

Instead, the light rays focus just in front of the retina, resulting in distant objects appearing blurred.

It's not clear exactly why this happens, but it often runs in families and has been linked to focusing on nearby objects, such as books and computers, for long periods during childhood.

Ensuring your child regularly spends time playing outside may help to reduce their risk of becoming short-sighted.

Treatments for short-sightedness

Short-sightedness can usually be corrected effectively with a number of treatments.

The main treatments are:

  • corrective lenses – such as glasses or contact lenses to help the eyes focus on distant objects
  • laser eye surgery to alter the shape of the eye – this isn't usually available on the NHS and shouldn't be carried out on children, whose eyes are still developing
  • artificial lens implants – where a man-made lens is permanently inserted into the eyes to help them focus correctly; these also aren't usually available on the NHS

Read more about treating short-sightedness.

Associated eye conditions

Some adults with severe short-sightedness and young children with untreated short-sightedness are more likely to develop other eye problems.

These can include:

  • a squint - a common childhood condition where the eyes point in different directions
  • a lazy eye - a childhood condition where the vision in one eye doesn't develop properly
  • glaucoma - increased pressure inside the eyes
  • cataracts - where cloudy patches develop inside the lens of the eye
  • retinal detachment - where the retina pulls away from the blood vessels that supply it with oxygen and nutrients

Who can get it

Short-sightedness (myopia) usually occurs when the eyes grow slightly too long, which means they're unable to produce a clear image of objects in the distance.

It's not clear exactly why this happens, but it's thought to be the result of a combination of genetic and environmental factors that disrupt the normal development of the eye.

How the eye works

Light passes through the cornea (the transparent layer at the front of the eye) and into the lens (the transparent structure that sits behind the cornea).

This focuses it on to the retina (a layer of light-sensitive tissue at the back of the eye) to create an image that's then sent to the brain.

To produce a perfectly clear image, the cornea should be evenly curved and the eye needs to be the right length. 

In people with short-sightedness, the eye has usually grown slightly too long.

This means that when you look at distant objects, the light isn't focused directly on to your retina, but a short distance in front of it.

This results in a blurry image being sent to your brain.

What increases your risk?

Although it's not clear exactly why some people become short-sighted, there are some things that can increase your chances of developing the condition.

Your genes

Short-sightedness is known to run in families, so you're more likely to develop it if one or both or your parents are also short-sighted.

Research has so far identified more than 40 genes linked to short-sightedness.

These are responsible for the eye's structure and development, and signalling between the brain and the eyes.

Too little time outdoors

Research has found that spending time playing outside as a child may reduce your chances of becoming short-sighted, and existing short-sightedness may progress less quickly.

This may be related to light levels outdoors being much brighter than indoors.

Both sport and relaxation outdoors appear to be beneficial in reducing the risk of short-sightedness.

Excessive close work

Spending a lot of time focusing your eyes on nearby objects, such as reading, writing and possibly using hand-held devices (phones and tablets) and computers can also increase your risk of developing short-sightedness.

An "everything in moderation" approach is therefore generally recommended.

Although children should be encouraged to read, they should also spend some time away from reading and computer games each day doing outdoor activities.

Diagnosis

You can find out if you have short-sightedness (myopia) by having an eye test at your local opticians.

Find an opticians near you.

You should have a routine eye test at least every two years, but you can book a test at any point if you have any concerns about your or your child's vision.

For some people - such as children under 16, or those under 19 and in full-time education - eye tests are available free of charge on the NHS.

What happens during an eye test

Your eyes will usually be tested by an optometrist (someone who's been specially trained to examine the eyes).

It can be difficult to examine young children's eyes, so they may sometimes need to be referred to a local hospital eye service for an eye test.

They may also need eye drops to dilate the pupil of the eye to get accurate measurements.

A number of different tests will usually be carried out as part of your eye test.

These may include:

  • measurements of the pressure inside your eyes
  • checks to measure how well your eyes work together
  • visual acuity tests where you're asked to read from a chart that has rows of letters that get smaller on each line
  • retinoscopy where a bright light is shone into your eye to see how it reacts

If the tests detect a possible problem with your distance vision, you may be asked to repeat the visual acuity tests while different strength lenses are placed in front of your eyes.

This will help the optometrist to determine what your glasses prescription should be.

Understanding your glasses prescription

If an eye test finds that you're short-sighted, you'll be given a prescription that describes what lenses you need to improve your vision.

This can be used to make glasses or contact lenses.

Your prescription will usually consist of 3 main numbers for each eye.

These are:

  • Sph (sphere) – a positive number here indicates that you're long-sighted, while a negative number indicates that you're short-sighted
  • Cyl (cylinder) – this number indicates whether you have astigmatism (where the front of your eye isn't perfectly curved)
  • Axis – this describes the angle of any astigmatism you have

If you're short-sighted, the Sph number is the most relevant. This is given in a measurement called dioptres (D), which describes how severely short-sighted you are.

A score of -0.5D to -3D is usually considered to be mild myopia, while a score of more than -6D is considered to be severe or high myopia.

Treatment

Glasses or contact lenses are the most common method of correcting short-sightedness (myopia). Laser surgery is also becoming increasingly popular.

Implanting artificial lenses in the eyes is a fairly new technique that's used very occasionally if laser surgery is ineffective or not possible (for example, people with very severe short-sightedness).

Corrective lenses

Glasses

Short-sightedness can usually be corrected using glasses made specifically to your prescription.

See diagnosing short-sightedness for more information about what your prescription means.

Wearing a lens made to your prescription will ensure light is focused onto the back of your eye (retina) correctly so distant objects don't appear as blurry.

The thickness and weight of the lenses you need will depend on how short-sighted you are.

Your eyesight often changes as you get older, which means you may eventually need to use 2 pairs of glasses: 1 pair for close vision activities such as reading, and the other pair for distance vision activities, such as watching television.

Some people prefer to use bifocal lenses that allow them to see objects clearly that are both close up and far away without changing their glasses.

You can also get multifocal lenses that help you see nearby objects and those at middle and long distances (varifocal glasses).

Contact lenses

Contact lenses can also be used to correct vision in the same way as glasses.

Some people prefer contact lenses to glasses because they're lightweight and almost invisible, but some people find them more of a hassle than wearing glasses.

Contact lenses can be worn on a daily basis and discarded each day (daily disposables), or they can be disinfected and reused.

They can also be worn for a longer period of time, although eye specialists generally recommend that contact lenses aren't worn overnight because of the risk of infection.

Some opticians very occasionally use a technique called orthokeratology. 

This involves wearing a hard contact lens overnight to flatten the curvature of the cornea (the transparent layer at the front of the eye) so you can see better without a lens or glasses during the day.

It's not a cure for short-sightedness because the cornea usually returns to its normal shape, but it may reduce reliance on lenses for some people.

Your optician can advise you about the most suitable type of contact lenses for you.

If you decide to wear contact lenses, it's very important that you keep your lenses clean and hygienic to prevent eye infections.

Availability and cost

You can get vouchers towards the cost of glasses or contact lenses if you're eligible – for example, if you're under 16 years old or you're receiving Income Support

If you're not eligible you'll have to pay for glasses or contact lenses. The prices of glasses can vary significantly, depending on your choice of frame. Entry-level glasses start at around £50, whereas designer glasses can cost several hundred pounds.

The cost of contact lenses will vary depending on your prescription and the type of lens you choose. They can range from £5-£10 a month for some monthly disposables, to £30-50 a month for some daily disposables.

Laser eye surgery

Laser eye surgery involves using a laser to burn away small sections of your cornea(s) to correct their curvature so that the light is better focused onto your retina.

There are three main types of laser eye surgery:

  • Photorefractive keratectomy (PRK) - where a small amount of the cornea's surface is removed and a laser is used to remove tissue and change the shape of the cornea.
  • Laser epithelial keratomileusis (LASEK) - similar to PRK but involves using alcohol to loosen the surface of the cornea, so a flap of tissue can be lifted out of the way, while a laser is used to alter the shape of the cornea, the flap is put back in place afterwards.
  • Laser in situ keratectomy (LASIK) - similar to LASEK, but a smaller flap of the cornea is created.

These procedures are usually carried out on an outpatient basis, so you won't normally have to stay in hospital overnight. The treatment usually takes less than 30 minutes to complete. A local anaesthetic is used to numb your eyes while it's carried out.

Which procedure is best?

All three laser eye surgery techniques produce similar results, but they tend to have different recovery times.

LASEK or LASIK are usually the preferred methods because they cause almost no pain and your vision will usually start to recover within a few hours or days. However, your vision may not fully stabilise for up to a month.

PRK can be a bit painful and it can take several months for your vision to stabilise afterwards.

LASIK can only be carried out if your cornea is thick enough. If your cornea is thin, the risk of complications occurring, such as loss of vision, is too great. LASEK and PRK may be possible if your cornea is not thick enough for LASIK surgery.

The Royal College of Ophthalmologists has published a Patient's Guide to Refractive Laser Surgery (PDF, 364kb) and also provides answers to specific questions related to laser refractive surgery (PDF, 196kb).

You can also read NICE guidance about laser surgery for the correction of refractive errors.

Results

The results of all three techniques are usually good. While it may not always be possible to completely cure your short-sightedness, around 9 out of 10 people experience a significant improvement in their vision and many are able to meet the minimum vision requirements for driving.

Most people who have laser surgery report that they are happy with the results. However, it's important to realise that laser surgery may not necessarily improve your vision to the same degree as wearing corrective lenses. Also as with any type of surgery, laser surgery carries risks of complications.

Risks and complications

Laser eye surgery does carry risks, including:

  • dry eyes - this will usually last a few months, during which time you can lubricate your eyes with special eye drops
  • removal of too much cornea tissue - this occurs in around 1 in 20 cases and could leave you with an eye that is long-sighted
  • reduced night vision - this usually passes within six weeks
  • a haze effect around bright lights - this will usually pass within 6 to 12 months

There's also a small risk of potentially serious complications that could threaten your vision, such as cornea becoming too thin or infected. However, these problems are rare, occurring in less than 1 in every 500 cases.

Make sure you understand all the risks involved before deciding to have laser eye surgery.

Who can't have laser surgery?

You shouldn't have any sort of laser eye surgery if you're under 21 years old because your vision may still be developing at this stage.

Even if you're over 21, laser eye surgery should only be carried out if your glasses or contact lens prescriptions hasn't changed significantly over the last two years or more.

Laser surgery may also not be suitable if you:

  • have diabetes – this can cause abnormalities in the eyes, which can be made worse by laser surgery to the cornea
  • are pregnant or breastfeeding – your body will contain hormones that cause slight fluctuations in your eyesight, making precise surgery difficult
  • have a condition that affects your immune system, such as HIV or rheumatoid arthritis – these conditions may affect your ability to recover after surgery
  • have other problems with your eyes, such as glaucoma (increased pressure in the eye) or cataracts (cloudy patches in the lens of the eye)

Laser eye surgery can generally be effective for people with a prescription of up to -10D. If your short-sightedness is more severe, lens implants may be more appropriate.

Availability and cost

Laser surgery isn't usually available on the NHS because other treatments, such as glasses or contact lenses, are considered to be equally, if not more, effective.

This means you'll usually have to pay for surgery privately.

Prices can vary depending on where you live, the individual clinic, and the type of equipment used during the procedure.

As a rough estimate, you usually have to pay somewhere around £800 to £1,500 for each eye.

Lens implant surgery

Lens implant surgery is a relatively new type of surgery for short-sightedness. It involves implanting an artificial lens into your eye theough a small cut in your cornea.

The lenses are specially designed to help focus light more clearly on to the retina. They can be helpful in improving the vision of people with very severe short-sightedness or those who have difficulty wearing glasses or contact lenses.

There are two main types of lens implant:

  • phakic implant, where an artifical lens is placed into your eye without removing your natural lens; usually preferred for younger people whose natural reading vision is normal
  • artificial replacement - where the natural lens is removed and replaced with an artificial one, similar to cataract surgery

Both types of implant are usually inserted under a local anaesthetic and you'll normally be able to return home the same day. Each eye will usually be treated on separate occassions.

Results

Phakic lens implants may achieve better results than lens replacements, in terms of improving vision on a long-term basis. However, the technique carries a higher risk of complications, such as cataracts.

Overall, most people will experience a significant improvement in their vision and around one in four may have almost completely normal vision ("20/20" vision) afterwards.

A lens replacement may be more suitable for older adults with damage to their eyes or an eye condition other than short-sightedness, such as cataracts or glaucoma.

Also, as both techniques are relatively new, there is little information about whether they are safe or effective in the long term.

Risk and complications

Like all medical procedures, surgery to place artificial lens implants in the eyes carries a risk of complications.

Posterior capsule opacification (PCO) is one of the most common complications of lens implant surgery. This is where part of the artificial lens becomes thickened and cloudy.

PCO usually occurs a few months or years after having surgery. Treatment for PCO can involve having laser surgery to remove the thickened part of the lens.

Other possible complications of lens implant surgery include:

  • retinal detachment (where the retina begins to pull away from the blood vessels that supply it with oxygen and nutrients)
  • cataracts
  • seeing a halo of light around objects at night
  • reduced night vision
  • glaucoma

You should talk to your doctor or surgeon about each procedure so you're fully aware of any risks involved.

Availability and cost

As with laser surgery, lens implant surgery isn't usually available on the NHS. Both types of surgery can be quite expensive. Many clinics quote prices of around £4,000 to £5,000 for treating both eyes.

Can I stop short-sightedness getting worse?

Unfortunately, short-sightedness in children tends to get worse as they grow.

The younger they are when they start becoming short-sighted, generally the faster their vision deteriorates and the more severe it is in adulthood. Short-sightedness usually stops getting worse at around 20 years of age.

There's currently no single treatment available that appears to stop this progression. However, it may be slowed by treatments involving eye drops of a medication called atropine, or special contact lenses.

Research has shown that atropine eye drops can slow the progression of short-sightedness, but it can cause side effects at high strengths - such as difficulty reading and sensitivity to bright light - and low-strength drops aren't commercially available in the UK.

Orthokeratology and bifocal contact lenses may also slow down short-sight progression in children, but possibly not as much as the eye drops, and they carry small risks.



The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website nhs.uk
Last Updated: 05/11/2021 09:44:14