From a- (negative prefix) + stem of Ancient Greek στίγμα (stígma, “mark, point”) + -ism. Coined by English polymath William Whewell in 1846.
释义
名词noun
1(optics) A 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(pathology) A disorder of the vision, usually due to a misshapen cornea, such that light does not focus correctly on the retina causing a blurred image.