Short-sightedness (myopia) is a problem of vision that causes distant objects to appear blurred, while close objects can still be seen clearly.
This is because light rays are being focused in front of the retina (the inside of the back of the eye), rather than directly on the retina.
The cause of myopia is the eye being too long from front to back, or the cornea (the front of the eye) being too steeply curved. The result is a mismatch between the length of the eye and its focusing power.
The degree of myopia is determined by the focusing power of the lens, which is measured in dioptres (D):
- mild-degree myopia is between 0.5D and 3.0D,
- medium-degree myopia is between 3.0D and 6.0D, and
- high-degree myopia is 6.0D and over.
How common is it?
At least five million British people are short-sighted and about 200,000 of them have high-degree myopia.
How is it treated?
Myopia can usually be corrected with glasses (spectacles) or contact lenses. Surgery to correct myopia is available, although most people pay for this privately (see Treatment section, above).
