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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 ...
Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes (or one blue eye and one brown eye ), a white forelock or patches of light skin. These basic features constitute type 2 of the condition; in type 1, there ...
Color blindness or color vision deficiency ( CVD) is the decreased ability to see color or differences in color. [ 2] The severity of color blindness ranges from mostly unnoticeable to full absence of color perception. Color blindness is usually an inherited problem or variation in the functionality of one or more of the three classes of cone ...
Keratoconus. Keratoconus ( KC) is a disorder of the eye that results in progressive thinning of the cornea. [ 3] This may result in blurry vision, double vision, nearsightedness, irregular astigmatism, [ 4] and light sensitivity leading to poor quality-of-life. [ 3][ 5] Usually both eyes are affected. [ 3] In more severe cases a scarring or a ...
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 ...
While the macula is preserved there is some loss of pigmentation around it. Retinitis pigmentosa ( RP) is a genetic disorder of the eyes that causes loss of vision. [ 1] Symptoms include trouble seeing at night and decreasing peripheral vision (side and upper or lower visual field). [ 1] As peripheral vision worsens, people may experience ...
A variety of human hair colors; from top left, clockwise: black, brown, blonde, white, red. Human hair color is the pigmentation of human hair follicles and shafts due to two types of melanin: eumelanin and pheomelanin. Generally, the more melanin present, the darker the hair. Its tone depends on the ratio of black or brown eumelanin to yellow ...
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 ...