Concave spectacles for myopia

What it is

Diverging lenses that corrected distance vision, added to the convex lenses for presbyopia dating from 1290. Florence became a centre of production, with lenses graded by age.

Documented in letters from the court of Milan (1462) commissioning lenses to 'see far'.

What it led to

• The trade of optician, with graded lenses and a trade in spectacles
• The grinding of concave lenses, essential for the Galilean telescope
• A longer working life for craftsmen and scholars

Built on

• Eyeglassesc. 1286
• Convex spectacles (Pisa/Venice, c. 1290)
• Venetian glass

Made possible

• Retinal image: the eye as an optical system (Kepler)1604
• Refracting telescope1608
• Compound microscopec. 1590-1625
• Spectacles with temple arms (1727)

Links