ABSTRACT
Human vision is based on the ability to perceive light, which enters the brain through the eye as shown in Figure 5.1. Light travels through a number of layers before hitting the area of the eye called the retina [16]. It is converted into nerve signals in photosensitive cells, which primarily consist of cones and rods. Cones are colorsensitive and require a lot of light to be triggered. They are most densely distributed in the foveal area of the retina, which is responsible for detailed vision. There are no rods in the the fovea. Rods are more densely distributed in peripheral areas of the retina, which contain significantly fewer cones. They are much more sensitive to light than cones and are therefore responsible for vision under low-light conditions. They are monochromatic and are also responsible for motion detection. Image resolution in the periphery is much lower than in the fovea also due to the pooling of information from retinal receptors by retinal ganglion cells, which is far greater in the visual periphery than in the foveal area [18]. The distribution of cones and rods on the retina takes into account the competing evolutionary requirements for a wide field of view and high-resolution vision. The light is carried into the brain through the ganglion cells and the optic nerve, which enters the retina at the optical disc.
