Eye

The eye is an optical system designed to create images on the retina. Its various components, such as the cornea, the aqueous humour, the iris, the lens and the vitreous humour, combine to enable the eye to react quickly and easily to different lighting levels that vary by factor 10⁵. Its sensitivity threshold is as low as 10^-12 lx (equivalent to the light from a faint star in the night sky).

Schematic cross-section through the eye