What is myopia?

This is nearsightedness (also called short-sighted in other countries) which means that you can see near, but have problems with distant objects. This usually occurs because the eye is too big, with images focusing in the middle of the eye in the vitreous cavity. It is treated with minus lenses (concave surface) which weakens the overall refractive power of the eye and allows images to focus properly on the retina.