The eye is a complex organ. The light rays entering the pupil, are projected by the lens into an image on the retina in the back of the eyeball. The pupil of the eyeball can be wider or narrower so that there is more or less light is incident on the retina. The image is transferred to the brains via the optic nerve, and that 'picture' we give a meaning.
The retina of an eye contains 137 million cells. The majority of cells which is in the form of a stick. As a result, we see black and white, we can look at dusk and we notice movements. The other 7 million cells have the shape of a cone, which we can see in the daylight colors and patterns. The center of the retina is known as the yellow spot. Here the cones are very close together. With this we see fine details.
The eyes keep themselves clean all day with tears in which a disinfectant dust sits. By flashing (about 20 times per minute) we spread tears over the eye. This keeps the eye clean, dust free and protects the eye from external influences.
Carrots good for the eyes
Certain nutrients can 'feed' eyes. And not just carrots.
In the root, but also in mango and apricot, is beta-carotene, which is converted in the body into vitamin A, which is also good for the eyes.
Rose hips are rich in vitamin C (like for example, kiwis and oranges), the vitamin protects against free radicals. The same is true for vitamin E (in nuts and fatty fish).
In meat, fish and shellfish is the mineral zinc, which contributes to the maintenance of normal vision.