You can find out if you have short-sightedness (myopia) by having an eye test at your local opticians.
You should have a routine eye test at least every 2 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.
Read about NHS eyecare entitlements to check if you qualify.
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:
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.
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.
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.