Myopia (or short - sightedness)
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’
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.