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Eye color. Eye color is a polygenic phenotypic trait determined by two factors: the pigmentation of the eye 's iris [1][2] and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris. [3]: 9. In humans, the pigmentation of the iris varies from light brown to black, depending on the concentration of ...
Heterochromia iridum. Heterochromia is a variation in coloration most often used to describe color differences of the iris, but can also be applied to color variation of hair [1] or skin. Heterochromia is determined by the production, delivery, and concentration of melanin (a pigment). It may be inherited, or caused by genetic mosaicism ...
Color vision. Color vision, a feature of visual perception, is an ability to perceive differences between light composed of different frequencies independently of light intensity. Color perception is a part of the larger visual system and is mediated by a complex process between neurons that begins with differential stimulation of different ...
The iris (pl.: irides or irises) is a thin, annular structure in the eye in most mammals and birds, responsible for controlling the diameter and size of the pupil, and thus the amount of light reaching the retina. In optical terms, the pupil is the eye's aperture, while the iris is the diaphragm.
Eye color is determined by a few different genetic factors, the most important being OCA2. ... All blue-eyed people can trace their ancestry back to a single human born between 6,000 and 10,000 ...
The human eye is a sensory organ in the visual system that reacts to visible light allowing eyesight. Other functions include maintaining the circadian rhythm, and keeping balance. Arizona Eye Model. "A" is accommodation in diopters. The eye can be considered as a living optical device. It is approximately spherical in shape, with its outer ...
The human eye, showing the iris and pupil. In 1802, philosopher William Paley called it a miracle of " design." In 1859, Charles Darwin himself wrote in his Origin of Species, that the evolution of the eye by natural selection seemed at first glance "absurd in the highest possible degree". [3] However, he went on that despite the difficulty in ...
Cone cells or cones are photoreceptor cells in the retinas of vertebrates' eyes. They respond differently to light of different wavelengths, and the combination of their responses is responsible for color vision. Cones function best in relatively bright light, called the photopic region, as opposed to rod cells, which work better in dim light ...