Myopia (or short - sightedness)

Myopia or nearsightedness is a refractive error that causes poor distance vision.
Near objects are usually seen clearly. In near-sighted people the eye is too long, or the cornea has too much focusing power.

If you have myopia, images focus on a point in front the retina. The light rays have past the correct focal point by the time they reach the retina. The retina then sends this "over-focused," blurry image to the brain.

This condition is a very common defect and affects about 25% of all people.
The physiological myopia often commences in early teenage years and stabilises around 20 years of age.
You are short-sighted when your spectacle prescription shows a minus sign in front of the number in the ‘sph’ box.

Although categorising myopia by strength of spectacle correction is a little arbitrary, generally it could be said that minus one to minus three dioptres (-1.00 to -3.00) represents milder myopia, between minus three and minus six dioptre (-3.25 to -6.00) is moderate myopia and greater than minus six dioptres is high myopia.