Memoirs of the American Philosophical Society 259. Philadelphia: American Philosophical Society, 2007. xvi + 378 pp. index. append. illus. bibl. $85. ISBN: 978-0-87169-259-7.
"More than three decades ago Vincent Ilardi, a diplomatic historian, discovered correspondence of the 1460s in which the Sforza court in Milan ordered eyeglasses in Florence. He published his findings in this journal in 1976. Ilardi argued that the large quantities of eyeglasses that the Dukes of Milan ordered in these letters showed that Florence was a leading manufacturer of eyeglasses in the fifteenth century. The orders were for convex lenses to correct presbyopia, specified according to categories of age from thirty to seventy years, as well as for concave lenses to correct myopia (in two grades). This was, in fact, the first mention in writing of concave eyeglasses, showing them to be readily available by the mid-fifteenth century. Convex eyeglasses had already been invented around 1286. "(Source: Sven Dupré, University of Ghent at the The Free Library website)
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