12/14/2023 0 Comments Genetic mutation purple eyes![]() ![]() Pigment dispersion syndrome – a condition characterized by loss of pigmentation from the posterior iris surface which is disseminated intraocularly and deposited on various intraocular structures, including the anterior surface of the iris.Oculodermal melanocytosis (nevus of Ota).Ocular melanosis – a condition characterized by increased pigmentation of the uveal tract, episclera, and anterior chamber angle.Lisch nodules – iris hamartomas seen in neurofibromatosis.Sometimes one eye may change color following disease or injury. Most cases of heterochromia are hereditary, or caused by genetic factors such as chimerism, and are entirely benign and unconnected to any pathology, however, some are associated with certain diseases and syndromes. Although a distinction is frequently made between heterochromia that affects an eye completely or only partially (sectoral heterochromia), it is often classified as either genetic (due to mosaicism or congenital) or acquired, with mention as to whether the affected iris or portion of the iris is darker or lighter. Heterochromia is classified primarily by onset: as either genetic or acquired. Classification Congenital heterochromia: inherited in autosomal dominant fashion (from men or women) In the United States, July 12 is observed by some as National Different Colored Eyes Day. The overall concentration of these pigments, the ratio between them, variation in the distribution of pigment in the layers of the stroma of the iris and the effects of light scattering all play a part in determining eye color. However, there are only two pigments present, eumelanin and pheomelanin. The color of the mammalian, including human, iris is very variable. Environmental or acquired factors can alter these inherited traits. Although the processes determining eye color are not fully understood, it is known that inherited eye color is determined by multiple genes. īackground Complete heterochromia in a humanĮye color, specifically the color of the irises, is determined primarily by the concentration and distribution of melanin. The term is derived from Ancient Greek: ἕτερος, héteros "different" and χρῶμα, chrôma "color". In humans, an increase of melanin production in the eyes indicates hyperplasia of the iris tissues, whereas a lack of melanin indicates hypoplasia. The affected eye may be hyperpigmented (hyperchromic) or hypopigmented (hypochromic). Though common in some breeds of cats, dogs, cattle and horses due to inbreeding, heterochromia is uncommon in humans, affecting fewer than 200,000 people in the United States, and is not associated with lack of genetic diversity. This is due to a mutation of the genes that determine melanin distribution at the 8-HTP pathway, which usually only become corrupted due to chromosomal homogeneity. Though multiple causes have been posited, the scientific consensus is that a lack of genetic diversity is the primary reason behind heterochromia, at least in domestic animals. In central heterochromia, there is a ring around the pupil or possibly spikes of different colors radiating from the pupil. In sectoral heterochromia, part of one iris is a different color from its remainder. In complete heterochromia, one iris is a different color from the other. Heterochromia of the eye is called heterochromia iridum or heterochromia iridis. It occurs in humans and certain breeds of domesticated animals. ![]() It may be inherited, or caused by genetic mosaicism, chimerism, disease, or injury. Heterochromia is determined by the production, delivery, and concentration of melanin (a pigment). 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 or skin. Iris implant surgery (controversial for cosmetic purposes) Max Scherzer photograph showing his complete heterochromiaĭifferent or partially different eye color ![]()
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