Vision occurs because visual rays or a visual power travels outward from the eyes to the object being seen.

“Rays coming out of the eyes” sounds like folklore, but extramission supported serious mathematical optics.

Euclid’s Optics used straight visual rays extending from the observer to construct a geometry of apparent size and perspective. Other ancient theories differed sharply. Aristotle was an intromissionist, atomists proposed images entering the eye, and Plato’s account was partly interactionist, so there was never one universal ancient theory of vision.

In the Latin West, however, extramission became highly influential. The eye was treated as an active participant whose visual power extended toward what it saw.

The major transformation came through Ibn al-Haytham (Alhazen). His Book of Optics replaced outgoing visual rays with a sophisticated account in which light travels from visible objects into the eye. After the work was translated into Latin around 1200, Roger Bacon, Witelo, John Pecham, and other perspectivists made intromission central to later medieval optical theory.

Modern vision science adds the physiology missing from both ancient geometrical camps: incoming light is focused onto retinal photoreceptors, converted into electrical signals, and processed through neural circuits.

Because ancient and medieval visual theories were highly pluralistic, this card is historically important but excluded from precise lifespan rankings.