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) Different or partially different eye color
0 kommentar(er)
