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Myopia, also known as near-sightedness and short-sightedness, 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. Myopia is most commonly corrected 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 term myopia is , ''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). The opposite of myopia is hyperopia (long-sightedness). ==Signs and symptoms== Myopia presents with blurry distance vision, but generally gives good near vision. In high myopia, even near vision is affected as objects must be extremely close to the eyes to see clearly, and people with myopia cannot read without their glasses prescribed for distance. On fundoscopic examination of the eye, the optic nerve appears to be tilted and an area of white sclera could be seen on next to the disc with a line of hyperpigmentation separating this area from normal retina. The macula will have some retinal pigmentary changes and sometimes will have subretinal hemorrhages. The retina in myopic patients is thin and thorough evaluation of the periphery might show retinal holes and lattice degeneration. In addition, people with myopia might develop choroidal neovascularization in the macula. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「myopia」の詳細全文を読む スポンサード リンク
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