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Heterochromia iridum

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Not to be confused with Heterochromatin.
Heterochromia iridum
SpecialtyOphthalmology Edit this on Wikidata
Complete heterochromia in human eyes: one brown and one hazel

In anatomy, heterochromia refers to a difference in coloration, usually of the iris but also of hair or skin. Heterochromia is a result of the relative excess or lack of melanin (a pigment). It may be inherited, due to genetic mosaicism, or due to disease or injury.[1]

Eye color, specifically the color of the irises, is determined primarily by the concentration and distribution of melanin.[2][3][4] The affected eye may be hyperpigmented (hyperchromic) or hypopigmented (hypochromic).[5] In humans, usually, an excess of melanin indicates hyperplasia of the iris tissues, whereas a lack of melanin indicates hypoplasia.

Heterochromia of the eye (heterochromia iridis or heterochromia iridum) is of two kinds. In complete heterochromia, one iris is a different color from the other. In partial heterochromia or sectoral heterochromia, part of one iris is a different color from its remainder.

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 syndrome.

Heterochromia in animals

Main article: Odd-eyed cat
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Although infrequently seen in humans, complete heterochromia is more frequently observed in other species, where it almost always involves one blue eye. The blue eye occurs within a white spot, where melanin is absent from the skin and hair (see Leucism). These species include the cat, particularly breeds such as Turkish Van, Turkish Angora, and (rarely) Japanese Bobtail. These so-called odd-eyed cats are white, or mostly white, with one normal eye (copper, orange, yellow, green), and one blue eye. Among dogs, complete heterochromia is seen often in the Siberian Husky. Horses with complete heterochromia have one brown and one white, gray, or blue eye - complete heterochromia is more common in horses with pinto coloring. Complete heterochromia occurs also in cattle and even water buffalo.[6] It can also be seen in ferrets with Waardenburg Syndrome.

Sectoral hypochromia in a blue merle Border Collie

Sectoral heterochromia, usually sectoral hypochromia, is often seen in dogs, specifically in breeds with merle coats. These breeds include Australian Shepherd and Border Collie.

Classification based on etiology

Heterochromia is classified primarily by onset: as either genetic or acquired. 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.[7]

Congenital heterochromia: inherited in autosomal dominant fashion (from men or women)

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 regarded as the affected eye as it usually shows iris hypoplasia. It may affect an iris completely or only partially.
  • Congenital Horner's syndrome[10] – sometimes inherited, although usually acquired
  • Waardenburg's syndrome[10] – a syndrome in which heterochromia presents as a bilateral iris hypochromia in some cases. A Japanese review of 11 albino children with the disorder found that all had sectoral/partial heterochromia.[11]
  • 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.[12]
  • Incontinentia pigmenti[5]
  • Parry-Romberg syndrome[5]

Acquired heterochromia

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

Abnormal iris darker

Abnormal iris lighter

  • Fuchs' heterochromic iridocyclitis – a condition characterized by a low grade, asymptomatic 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. The prevalence of heterochromia associated with Fuch's has been estimated in various studies[13][14][15] with results suggesting that there is more difficulty recognizing iris color changes in dark-eyed individuals.[15][16]
  • Acquired Horner's syndrome – usually acquired, as in neuroblastoma,[17] 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.

Heterochromia has also been observed in those with Duane syndrome.[18][19]

Central heterochromia

Example of Central Heterochromia showing a brown to blue iris.

Whereas heterochromia (also known as a heterochromia iridis or heterochromia iridum) is an eye condition in which one iris is a different color from the other (complete heterochromia), central heterochromia is an eye condition in which there are two different colors in the same iris. Central heterochromia is where the central (pupillary) zone of the iris is a different color than the mid-peripheral (ciliary) zone.

Eye color is determined primarily by the concentration and distribution of melanin pigment within the iris tissues, anything affecting those factors may result in a difference of color being observed.[20]

The human iris can be seen in a number of various colors. There are three true colors in the eyes that determine the outward appearance; brown, yellow, and grey. How much of each color an individual has determines the appearance of his or her eye color.[21]

Eyes displaying central heterochromia are often referred to as "cat eyes" because of the appearance of a multi-colored iris. Central heterochromia appears to be prevalent in irises containing low amounts of melanin.[22] Central heterochromia does not label an eye as hazel. This is because the outer ring of an eye affected by central heterochromia is that iris's true color.

  • Sectoral heterochromia: a blue iris with a brown section.
    Sectoral heterochromia: a blue iris with a brown section.
  • Complete heterochromia in a cat: one eye blue, one yellow. The yellow eye has what looks like Sectoral heterochromia, as the outside of the eye is yellow, and the iris is green.
    Complete heterochromia in a cat: one eye blue, one yellow. The yellow eye has what looks like Sectoral heterochromia, as the outside of the eye is yellow, and the iris is green.
  • Complete heterochromia in a dog: one eye blue, one eye brown.
    Complete heterochromia in a dog: one eye blue, one eye brown.
  • Complete heterochromia in a dog
    Complete heterochromia in a dog
  • Heterochromia in man
    Heterochromia in man
  • Musician David Bowie is noted for his acquired apparent Heterochromia (as a result of injury). Both eyes are the same color, though one is permanently dilated.
    Musician David Bowie is noted for his acquired apparent Heterochromia (as a result of injury). Both eyes are the same color, though one is permanently dilated.
  • Tempelton
    Tempelton

See also

References

  1. ^ Imesch PD, Wallow IH, Albert DM. "The color of the human eye: a review of morphologic correlates and of some conditions that affect iridial pigmentation." Surv Ophthalmol. 1997 Feb;41 Suppl 2:S117-23. PMID 9154287.
  2. ^ Wielgus AR, Sarna T. "Melanin in human irides of different color and age of donors." Pigment Cell Res. 2005 Dec;18(6):454-64. PMID 16280011.
  3. ^ Prota G, Hu DN, Vincensi MR, McCormick SA, Napolitano A. "Characterization of melanins in human irides and cultured uveal melanocytes from eyes of different colors." Exp Eye Res. 1998 Sep;67(3):293-9. PMID 9778410.
  4. ^ "All About Eye Color" from Larry Bickford
  5. ^ a b c d e f g h i Loewenstein, John; Scott Lee (2004). Ophthalmology: Just the Facts. New York: McGraw-Hill. ISBN 0-07-140332-9.
  6. ^ Misk NA, Semieka MA, Fathy A. "Heterochromia iridis in water buffaloes (Bubalus bubalis)." Vet Ophthalmol. 1998;1(4):195-201. PMID 11397231.
  7. ^ Swann P. "Heterochromia." Optometry Today. January 29, 1999. Accessed November 1, 2006.
  8. ^ van Emelen C, Goethals M, Dralands L, Casteels I. "Treatment of glaucoma in children with Sturge-Weber syndrome." J Pediatr Ophthalmol Strabismus. 2000 Jan-Feb;37(1):29-34. PMID 10714693.
  9. ^ Sturge-Weber syndrome: Definition and Much More from Answers.com
  10. ^ a b Wallis DH, Granet DB, Levi L. "When the darker eye has the smaller pupil." J AAPOS. 2003 Jun;7(3):215-6. PMID 12825064.
  11. ^ Ohno N, Kiyosawa M, Mori H, Wang WF, Takase H, Mochizuki M. "Clinical findings in Japanese patients with Waardenburg syndrome type 2." Jpn J Ophthalmol. 2003 Jan-Feb;47(1):77-84. PMID: 12586183.
  12. ^ Brazel SM, Sullivan TJ, Thorner PS, Clarke MP, Hunter WS, Morin JD. "Iris sector heterochromia as a marker for neural crest disease." Arch Ophthalmol. 1992 Feb;110(2):233-5. PMID 1736874
  13. ^ Yang P, Fang W, Jin H, Li B, Chen X, Kijlstra A. "Clinical features of Chinese patients with Fuchs' syndrome." Ophthalmology. 2006 Mar;113(3):473-80. Epub 2006 Feb 3. PMID 16458965.
  14. ^ Arellanes-Garcia L, del Carmen Preciado-Delgadillo M, Recillas-Gispert C. "Fuchs' heterochromic iridocyclitis: clinical manifestations in dark-eyed Mexican patients." Ocul Immunol Inflamm. 2002 Jun;10(2):125-31. PMID 12778348.
  15. ^ a b Tabbut BR, Tessler HH, Williams D. "Fuchs' heterochromic iridocyclitis in blacks." Arch Ophthalmol. 1988 Dec;106(12):1688-90. PMID 3196209.
  16. ^ Bloch-Michel E. "[Fuchs heterochromic cyclitis: current concepts.]" J Fr Ophtalmol. 1983;6(10):853-8. PMID 6368659.
  17. ^ Mehta K, Haller JO, Legasto AC. "Imaging neuroblastoma in children." Crit Rev Comput Tomogr. 2003;44(1):47-61. PMID 12627783.
  18. ^ Khan AO, Aldamesh M. "Bilateral Duane syndrome and bilateral aniridia." J AAPOS. 2006 Jun;10(3):273-4. PMID 16814183.
  19. ^ Shauly Y, Weissman A, Meyer E. "Ocular and systemic characteristics of Duane syndrome." J Pediatr Ophthalmol Strabismus. 1993 May-Jun;30(3):178-83. PMID 8350229.
  20. ^ Wielgus AR, Sarna T. "Melanin in human irides of different color and age of donors." Pigment Cell Res. 2005 Dec;18(6):454-64
  21. ^ Seddon JM, Sahagian CR, Glynn RJ, Sperduto RD, Gragoudas ES. "Evaluation of an iris color classification system." The Eye Disorders Case-Control Study Group. Invest Ophthalmol Vis Sci. 1990 Aug;31(8):1592-8. PMID: 2201662
  22. ^ Key Ocular Signs for Screening
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