Macula of retina is seen when viewed from the pupil, as in ophthalmoscopy or retinal photography. The anatomical macula is defined histologically in terms of having two or more layers of ganglion cells. The umbo is the center of the foveola which in turn is located at the center of the fovea. The fovea is located near the center of the macula. It is a small pit that contains the largest concentration of cone cells. The retina contains two types of photosensitive cells, the rod cells and the cone cells. Because the macula is yellow in colour it absorbs excess blue and ultraviolet
Evolution of the eye behaviors have been identified, in two primary groups: Below 450 nm, associated with direct light, and above 450 nm, associated with reflected light. As opsin molecules were tuned to detect different wavelengths of light, at some point color vision developed when the photoreceptor cells used differently tuned opsins. This may have happened at any of the early stages of the eye's evolution, and may have disappeared and reevolved as organisms became predator or prey. Similarly, night and day vision emerged when photoreceptor cells differentiated into rods and cones, respectively. As discussed earlier, the properties of light under water differ from