Photoreceptors
"The cones and rods have characteristic morphological and functional differences. The outer segments of cones and rods consist of modified cilia that contain disc membranes, which contain the photopigment. The photopigment in rods is rhodopsin. Cones have three different kinds of photopigment, one for each of the three principle colors, blue, green and red. Rods account for vision in lovw light (scotopic vision). Cones have a lower sensitivity than the rods and are activated in medium and bright light (photopic vision). Because cones are the basis for color vision, a certain level of light above visual threshold is necessary to see colors. The human retina has approximately 20 times more rods than cones. The density of cones is highest density of rods is found at the location where the peripheral visual field is projected (the fovea)." pp. 377-339
Møller, Aage R. Sensory Systems: Anatomy, Physiology and Pathophysiology. Academic Press, 2002.
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The fovea is an interesting attribute to the eye, since it most immediately illustrate the power of thought over that of the scientific constructs in reality. There is something artistic about the way our brain constructs a reality based on its flaws and memories of the past.
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