The eye

The eye is basically a mechanism for receiving light and transforming it into electrical energy. The receptors in the eye transform it into electrical signals, which are passed on to the brain. The eye has a lot of components. The cornea and lens at the front of the eye focus the light into a sharp image on the back of the eye, the retina. The retina is made up of rods and cones.

Rods are highly sensitive to light and allow us to see under low levels of illumination. However, they are unable to resolve fine detail and are subject to saturation. This is the reason for the temporary blindness that is caused when we move from a dark room into sunlight. There are approximately 120 million rods per eye which are mainly situated towards the edges of the retina.

Cones are less sensitive to light than rods and can tolerate more light. There are three types of cones, each of which is sensitive to a different wavelength of light. These cones which number about 6 million are mainly concentrated on the fovea, a small area of the retina on which images are formed.