Eyeglasses Were Invented in Italy in the Late 1200s

A flaw of about two micrometers left early images blurry until astronauts installed corrective optics in 1993.

In the early 11th century he argued that vision works by light entering the eye and used experiments to show it.

Where the optic nerve leaves the retina there are no light-detecting cells, but the brain fills in the gap.

Light refracts as it enters a drop, reflects off the back and splits into colors as it leaves.