How does the eye work?

Light reflected from objects enters the eye by passing through the cornea, pupil and lens, finishing its course on the retina. The cornea is the first lens that encounters light; its function is to properly converge light rays within the eye. The iris bears at its centre the pupil, constitutes a diaphragm that, depending on the ambient light, is able to adjust the amount of it enters the eye thus also affecting the depth of field. In doing so, the iris makes sure that the light hits, as needed, only the cones (distinct full-light vision) or also the rods (black-and-white vision, not very distinct but useful for orientation in dimly lit environments). The lens, is a flexible lens, and allows objects to be focused. Light then reaches the retina that can transform a light signal into an electrical signal. In order for images to be perceived, the electrical impulse must be transported to the brain for processing, and this is done through the optic nerve.

The eye and the camera

Given its structure and operation, the eye is often compared to a camera, as can be seen in the image below:

1. Cornea: the outermost and most fixed lens
2. Iris: the diaphragm that regulates the amount of light entering the interior of the chamber
3. Crystalline: the group of movable lenses useful for focusing
4. Retina: the sensor of digital machines that can transform a light signal into an electrical signal
5. Optic nerve: the connecting cord through which nerve stimulus is transported to the brain
6. Brain: the computer, where the image is processed and finally perceived