Nearsightedness, or myopia, is a relatively frequent vision weakness. In most cases it is caused by the lengthening of the eyeball or too much light refraction in the eye. The light does not focus on the retina, but the focus is in front of the retina. This means that looking at a distance, the retina receives only a blurry picture.
Patients suffering from this condition have difficulty seeing objects at a distance; the picture is blurry and unclear. Nearsighted people can however see things up close. Similar to presbyopia , advanced nearsightedness is expressed in diopters, however with a negative symbol (i.e. -3 dpt).