Heterochromia

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In anatomy, heterochromia refers to a difference in coloration, usually of the irises but also of hair or skin.

Heterochromia (also known as a heterochromia iridis or heterochromia iridium) is an ocular condition in which one iris is a different color from the other (complete heterochromia), or where part of one iris is a different color from the remainder (partial heterochromia or sectoral heterochromia). It is a result of the relative excess or lack of pigment within an iris or part of an iris, which may be inherited or acquired by disease or injury[1].

Image:Sectoral heterochromia.jpg Eye color, specifically the color of the irises, is determined primarily by the concentration and distribution of melanin pigment within the iris tissues[2]. Consequently, anything affecting those factors may result in a difference of color being observed.

An excess of pigmentation is usually associated with hyperplasia of the iris tissues whereas a lack of pigmentation is associated with hypoplasia. Although seen in humans, heterochromia in which one iris differs in color from the other iris is more frequently observed in non-human species such as cats (for example, Japanese Bobtails; white, shorthaired cats can be "odd-eyed" with one copper or orange eye and one blue eye), dogs (for example, Siberian Huskies as well as Australian Shepherds, Border Collies, and other breeds with merle coats), and horses (so-called "walled-eyed" horses have one brown and one white eye). Partial or sectoral heterochromia is much less common than complete heterochromia and is typically found in autosomally inherited disorders such as Hirschsprung's disease and Waardenburg's syndrome. Image:DogEye2color cr wb.jpg

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Classfication based on etiology

Although a distinction is frequently made between heterochromia that affects an eye completely or only partially, it is often classified as either congenital or acquired with mention as to whether the affected iris or portion of the iris is darker or lighter.

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Congenital heterochromia

Heterochromia that is congenital is usually inherited as an autosomal dominant trait.

Abnormal iris darker
Abnormal iris lighter
  • Simple heterochromia - a rare condition characterized by the absence of other ocular or systemic problems. The lighter eye is typically regarding as the affected eye as it usually shows iris hypoplasia. It may affect an iris completely or only partially.
  • Congenital Horner's syndrome - sometimes inherited, although usually acquired
  • Waardenburg's syndrome - a syndrome in which heterochromia presents as a bilateral iris hypochromia in some cases.
  • Piebaldism - similar to Waardenburg's syndrome, a rare disorder of melanocyte development characterized by a white forelock and multiple symmetrical hypopigmented or depigmented macules.
  • Hirschsprung's disease - a bowel disorder associated with heterochromia in the form of a sector hypochromia. The affected sectors have been shown to have reduced numbers of melanocytes and decreased stromal pigmentation. [4]
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Acquired heterochromia

Heterochromia that is acquired is usually due to injury, inflammation, the use of certain eyedrops, or tumors.

Abnormal iris darker
  • Deposition of material
    • Siderosis - iron deposition within ocular tissues due to a penetrating injury and a retained iron-containing, intraocular foreign body.
    • Hemosiderosis - long standing hyphema (blood in the anterior chamber) following blunt trauma to the eye may lead to iron deposition from blood products
  • Use of certain eyedrops - prostaglandin analogues (latanoprost, isopropyl unoprostone, travoprost, and bimatoprost) are used topically to lower intraocular pressure in glaucoma patients. A concentric heterochromia has developed in some patients applying these drugs. The stroma around the iris sphincter muscle becomes darker than the peripheral stroma. A stimulation of melanin synthesis within iris melanocytes has been postulated.
  • Neoplasm - Nevi and melanomatous tumors.
Abnormal iris lighter
  • Fuchs' heterochromic iridocyclitis - a condition characterized by a low grade, a symptomatic uveitis in which the iris in the affected eye becomes hypochromic and has a washed-out, somewhat moth eaten appearance. The heterochromia can be very subtle, especially in patients with lighter colored irides. It is often most easily seen in daylight.
  • Acquired Horner's syndrome - usually acquired, as in neuroblastoma, although sometimes inherited.
  • Neoplasm - Melanomas can also be very lightly pigmented, and a lighter colored iris may be a rare manifestation of metastatic disease to the eye.
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Examples

Image:Cat - different coloured eyes.JPG Image:Bi-eyehusky.JPG

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Celebrities

  • Gracie Allen, was described as having one green eye and one blue eye in her widower, George Burns' autobiography. She stopped making movies once they became colourized.
  • David Bowie naturally born with two blue eyes, but after experiencing a childhood injury now has a permanently dilated left eye that appears brown and green depending on the light.
  • Kate Bosworth has sectoral heterochromia; two blue eyes with a hazel section at the bottom of her right eye (see [5], [6]).
  • Jane Seymour has a left green eye and right brown eye (see [7], [8])
  • Mila Kunis has a left green eye and right blue eye (see [9]).
  • Dan Aykroyd has one blue eye and one brown eye. (see [10])
  • Jessica Cauffiel has sectoral heterochromia, two green eyes with brown pigmentation on left eye (see [11]).
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External links

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See also

fr:Hétérochromie ja:虹彩異色症 sv:Heterokromi zh:虹膜異色症

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