Catherine Ann Bosworth, or well known as Kate Bosworth is an American actress who has a rare phenomenon. Kate Bosworth eyes have different colors. The color of her left eye is blue; meanwhile the right eye has a goldish brown hue on the bottom. The phenomenon of Kate Bosworth eyes is scientifically called Heterochromia Iridium. Usually heterochromia refers to the difference in the color, usually of the iris but also of hair or skin. Heterochromia is the result of the relative excess or lack of a pigment named melanin. This phenomenon may be casused by the genetic factors or by disease or injury.
Eye colors are determined primarily by the concentration and distribution of melanin.
An excess of melanin in human eyes indicates hyperplasia of the iris tissues, and a lack of melanin indicates hypoplasia. There are two kinds of heterochromia iridis or heterochromia iridum, complete and sectoral heterochromia. One iris is in different color from the other in complete heterochromia; meanwhile, in partial or sectoral heterochromia, part of one iris is in different color from its remainder. Heterochromia can also be classified by onset, whether it is genetic or acquired. Genetic or congenital heterochromia is inherited in autosomal dominant trait. Meanwhile, acquired heterochromia is usually caused by injury, inflammation, the use of certain eyedrops, or tumors.
The example of genetic or congenital heterochromia is pigment dispersion syndrome. This syndrome is a condition characterized by the loss of pigmentation from the posterior iris surface which is disseminated by way of intraocular and deposited on various intraocular structures, including the anterior surface of the iris. Another example is what is called as Hirschsprung’s disease. This is a bowel disorder which is associated with heterochromia in the form of a sector hypochromia where the numbers of melanocytes and stromal pigmentation decrease.
The example of acquired heterchromia is Fuchs heterochromic iridocyclitis. It refers to a condition indicated by a low grade, asymptomatic uveitis where the iris in the affected eye becomes hypochromic and has a washed-out, just like eaten by moths. This type of heterochromia can be very subtle, especially in patients with lighter colored irises. The result of various studies suggested that there is more difficulty recognizing iris color changes in dark-eyed individuals.
Beside those two types, we also have central heterochromia. It is an eye condition where there are two colors in the same iris. The central (pupillary) zone of the iris is different from the mid-peripheral (ciliary) zone. It is often called as often referred to as “cat eyes” because of the appearance of a multi-colored iris. This type of heterchromia is caused by the low amount of melanin.