What is myopia/short sight and how can it be corrected?
A person with myopia or short sight can see clearly objects close to them clearly, but not far away.
Myopia is caused by the shape of the eye; either the eyeball is slightly too long or the cornea (the clear covering of the front of the eye) is too steeply curved.
Myopia is corrected by spectacles or contact lenses with lenses which are 'minus' or concave in shape.
So if you're short sighted, your prescription will have a minus lens power, e.g. -2.50D.