Definition of "eyeglasses"

Digging deeper, the invention of eyeglasses is an elaboration of the more fundamental development of optics technology. The ability of a segment of a glass sphere to magnify whatever is placed before it was known around the year 1000, when the spherical segment was called a reading stone, […].

2013 September-October, Henry Petroski, “The Evolution of Eyeglasses”, in American Scientist, United States: Sigma Xi