Deals with the history of eyeglasses from their invention in Italy ca. 1286 to the appearance of the telescope three cent. later. "By the end of the 16th cent. eyeglasses were as common in western and central Europe as desktop computers are in western developed countries today." Eyeglasses served an important technological function at both the intellectual and practical level, not only easing the textual studies of scholars but also easing the work of craftsmen/small bus. During the 15th cent. two crucial developments occurred: the ability to grind convex lenses for various levels of presbyopia and the ability to grind concave lenses for the correction of myopia. As a result, eyeglasses could be made almost to prescription by the early 17th cent. Illus.