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The irises of human eyes exhibit a wide spectrum of colours. 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.
Heterochromia is determined by the production, delivery, and concentration of melanin (a pigment). It may be inherited, or caused by genetic mosaicism, chimerism, disease, or injury. [2] It occurs in humans and certain breeds of domesticated animals. Heterochromia of the eye is called heterochromia iridum or heterochromia iridis. It can be ...
Periorbital hyperpigmentation, also known as hereditary dark circles, is characterized by darker skin around the eyes caused by the presence of additional melanin. It is an extremely common hereditary human characteristic and is frequently found on individuals with dark skin. Periorbital hyperpigmentation is most prevalent within the 16–25 ...
Eumelanin is a black and brown pigment, whereas pheomelanin is a red and yellow pigment. The interaction between the two types, along with the amount of melanin present in the iris, determines ...
Heredity of phenotypic traits: a father and son with prominent ears and crowns. DNA structure. Bases are in the centre, surrounded by phosphate–sugar chains in a double helix. In humans, eye color is an example of an inherited characteristic: an individual might inherit the "brown-eye trait" from one of the parents. [1]
Some genetic conditions that result in a "leucistic" appearance include piebaldism, Waardenburg syndrome, vitiligo, Chédiak–Higashi syndrome, flavism, isabellinism, xanthochromism, axanthism, amelanism, and melanophilin mutations. Pale patches of skin, feathers, or fur (often referred to as "depigmentation") can also result from injury.
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.
Acute posterior multifocal placoid pigment epitheliopathy (APMPPE) is an acquired inflammatory uveitis that belongs to the heterogenous group of white dot syndromes in which light-coloured (yellowish-white) lesions begin to form in the macular area of the retina.