 Scattered evidence exists for use of visual aid devices in Greek and Roman times, most prominently the use of an emerald by emperor Nero as mentioned by Pliny the Elder.The use of a convex lens to form an enlarged/magnified image was most likely described in Ptolemy's "Optics" (which however only survives in a poor Arabic translation).Ptolemy's description of lenses was commented upon and improved by Ibn Sahl (10th century) and most notably by Alhazen ("Book of Optics", ca.