Myopia (Shortsightedness) is when the eyeball is too long for the focusing power of the cornea and lens combined.

Theoretically this means that the focus of light falls 'infront' of the retina and the person experiences visual blur. For clear vision to occur the light coming into the eyes needs to be focused sharply on the retina. The retina is the part of the eye that sends the visual image to the brain. It is more common for someone with Myopia to expericne blur in the distance, but if the Myopia reaches a certain value, they will expericne blur even when performing near acitivites like reading. Myopia can easily be corrected with lenses in glasses or contact lenses.