What is Nearsightedness?
Myopia (, muōpia, from myein "to shut (like a mole - mys/mus in Greek)" – ops (gen. opos) "eye, look, sight"), literally meaning "trying to see like a mole" (mys/mus), commonly known as near-sightedness (American English) and short-sightedness (British English), is a condition of the eye where the light that comes in does not directly focus on the retina but in front of it, causing the image that one sees when looking at a distant object to be out of focus, but in focus when looking at a close object.
When used colloquially, 'myopia' can also refer to a view on or way of thinking about something which is—by extension of the medical definition—hyper-focused and fails to include a larger context beyond the focus.
Eye care professionals most commonly correct myopia through the use of corrective lenses, such as glasses or contact lenses. It may also be corrected by refractive surgery, though there are cases of associated side effects. The corrective lenses have a negative optical power (i.e. have a net concave effect) which compensates for the excessive positive diopters of the myopic eye. Negative diopters are generally used to describe the severity of the myopia, as this is the value of the lens to correct the eye. High-degree myopia, or severe myopia, is defined as -6 diopters or worse.
The opposite of myopia is hyperopia (long-sightedness).