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Amblyopia (from Greek αμβλυωπία, "blunt vision"), also called lazy eye, is a disorder of sight. It results in decreased vision in an eye that otherwise appears normal, or out of proportion to associated structural problems of the eye. Whenever the brain does not receive visual signals from an eye for a long period of time, there is a risk of amblyopia. It also can occur when the brain "turns off" the visual processing of one eye to prevent double-vision, for example in strabismus (crossed eyes). The cause of amblyopia is within the brain. Detecting the condition in early childhood increases the chance of successful treatment, especially if detected before the age of five. The earlier it is detected, and the underlying cause corrected with glasses or surgery, the better the long term outcomes. This disorder has been estimated to affect 1–5% of the population. It often occurs during early childhood. ==Signs and symptoms== Many people with amblyopia, especially those who only have a mild form, are not even aware they have the condition until tested at older ages, since the vision in their stronger eye is normal. People who have ''severe'' amblyopia, however, may experience related visual disorders, most notably poor depth perception. Those with amblyopia may suffer from poor visual acuity, poor spatial acuity, low sensitivity to contrast and motion. Amblyopia is characterized by several functional abnormalities in spatial vision, including reductions in visual acuity (VA), contrast sensitivity function (CSF), and vernier acuity as well as spatial distortion, abnormal spatial interactions, and impaired contour detection. In addition, individuals with amblyopia suffer from binocular abnormalities such as impaired stereoacuity (stereoscopic acuity) and abnormal binocular summation.〔http://www.ncbi.nlm.nih.gov/pmc/articles/PMC404107/〕 Also, a crowding phenomenon is present.〔A study of separation difficulty. Its relationship to visual acuity in normal and amblyopic eyes.〕 These deficits are usually specific to the amblyopic eye. However, sub-clinical deficits of the "better" eye have also been demonstrated. People with amblyopia also have problems of binocular vision such as limited stereoscopic depth perception and usually have difficulty seeing the three-dimensional images in hidden stereoscopic displays such as autostereograms. Perception of depth, however, from monocular cues such as size, perspective, and motion parallax remains normal. 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「amblyopia」の詳細全文を読む スポンサード リンク
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