These spectacles have thick rims of horn surrounding the lenses. This type of frame was developed in the 1750s by Benjamin Martin (1704-1782), a London scientific instrument maker who felt that other spectacles let too much light into the eye. In his “Essay on Visual Glasses” Martin wrote that “Action of Light upon the Eye tends gradually to weaken it, the common Size of Spectacle-Glasses pours in upon the Eye-Ball three Times as much as is necessary for this Purpose; and therefore is very prejudicial to the Eye in this Respect, as in Time it makes them weak and watry.” The thicker horn rims made the lenses smaller in diameter than those set in metal frames.