- 1散光
Astigmatism is a common way the eye is shaped that stops seeing from being sharp. In a typical eye, the clear front surface is evenly curved, so light meets at one point at the back. With astigmatism that surface — or the lens inside — is a little steeper one way than the other, more like a rugby ball than a round football, so light does not meet at a single point. Lines in one direction can look clearer than lines the other way; lights may look streaky or doubled; things just will not go crisp, near or far. It is not a disease you catch, and it is not “tired eyes.” A lot of people have a little of it together with short sight or long sight. Glasses, contact lenses, or (for some adults) surgery can correct it. Opticians talk about it all the time.
組成Coined in 1846 by William Whewell: a- (“not, without”) + the stem of Greek στίγμα (a point, a mark) + -ism. The name means the eye does not bring light to one point.
同家族的字
- stigmasame Greek στίγμα “point, mark” — here “without a point of focus.” Today stigma usually means a mark of shame, a different use of the same old piece
原始詞典資料2 筆記錄
以下是外部詞典記錄的用法，摘錄並精簡格式，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
astigmatismnoun/əˈstɪɡmətɪzm̩/
- 1
engineeringnatural-sciencesopticsA defect of a lens such that light rays coming from a point do not meet at a focal point so that the image is blurred.
- 2
medicinepathologysciencesA disorder of the vision, usually due to a misshapen cornea, such that light does not focus correctly on the retina causing a blurred image.
摘錄自 英文維基詞典 English Wiktionary，已精簡格式；依 CC BY-SA 4.0 授權使用，改動後的內容同樣以此授權提供。