Heterochromia iridum

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Not to be confused with Heterochromatin or Dichromatic (disambiguation). Heterochromia iridum_sentence_0

Heterochromia iridum_table_infobox_0

HeterochromiaHeterochromia iridum_header_cell_0_0_0
SpecialtyHeterochromia iridum_header_cell_0_1_0 Ophthalmology Q461486?uselang=en#P1995Heterochromia iridum_cell_0_1_1
SymptomsHeterochromia iridum_header_cell_0_2_0 different or partially different eye colourHeterochromia iridum_cell_0_2_1
DurationHeterochromia iridum_header_cell_0_3_0 life-longHeterochromia iridum_cell_0_3_1
TreatmentHeterochromia iridum_header_cell_0_4_0 iris implant surgery (controversial for cosmetic purposes)Heterochromia iridum_cell_0_4_1

Heterochromia is a variation in coloration. Heterochromia iridum_sentence_1

The term is most often used to describe color differences of the iris, but can also be applied to color variation of hair or skin. Heterochromia iridum_sentence_2

Heterochromia is determined by the production, delivery, and concentration of melanin (a pigment). Heterochromia iridum_sentence_3

It may be inherited, or caused by genetic mosaicism, chimerism, disease, or injury. Heterochromia iridum_sentence_4

It occurs in humans and certain breeds of domesticated animals. Heterochromia iridum_sentence_5

Heterochromia of the eye is called heterochromia iridum or heterochromia iridis. Heterochromia iridum_sentence_6

It can be complete or sectoral. Heterochromia iridum_sentence_7

In complete heterochromia, one iris is a different color from the other. Heterochromia iridum_sentence_8

In sectoral heterochromia, part of one iris is a different color from its remainder. Heterochromia iridum_sentence_9

In central heterochromia, there is a ring around the pupil or possibly spikes of different colors radiating from the pupil. Heterochromia iridum_sentence_10

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. Heterochromia iridum_sentence_11

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. Heterochromia iridum_sentence_12

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. Heterochromia iridum_sentence_13

The affected eye may be hyperpigmented (hyperchromic) or hypopigmented (hypochromic). Heterochromia iridum_sentence_14

In humans, an increase of melanin production in the eyes indicates hyperplasia of the iris tissues, whereas a lack of melanin indicates hypoplasia. Heterochromia iridum_sentence_15

The term is from Ancient Greek: ἕτερος, héteros 'different' and χρῶμα, chrôma 'color'. Heterochromia iridum_sentence_16

Background - how eye color is determined Heterochromia iridum_section_0

Eye color, specifically the color of the irises, is determined primarily by the concentration and distribution of melanin. Heterochromia iridum_sentence_17

Although the processes determining eye color are not fully understood, it is known that inherited eye color is determined by multiple genes. Heterochromia iridum_sentence_18

Environmental or acquired factors can alter these inherited traits. Heterochromia iridum_sentence_19

The color of the mammalian, including human, iris is very variable. Heterochromia iridum_sentence_20

However, there are only two pigments present, eumelanin and pheomelanin. Heterochromia iridum_sentence_21

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. Heterochromia iridum_sentence_22

Classification Heterochromia iridum_section_1

Heterochromia is classified primarily by onset: as either genetic or acquired. Heterochromia iridum_sentence_23

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 iridum_sentence_24

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. Heterochromia iridum_sentence_25

Sometimes one eye may change color following disease or injury. Heterochromia iridum_sentence_26

Sectoral or partial heterochromia Heterochromia iridum_section_2

In sectoral heterochromia, sometimes referred to as partial heterochromia, areas of the same iris contain two completely different colors. Heterochromia iridum_sentence_27

It is unknown how rare sectoral heterochromia is in humans. Heterochromia iridum_sentence_28

Abnormal iris darker Heterochromia iridum_section_3

Heterochromia iridum_unordered_list_0

  • Lisch nodules – iris hamartomas seen in neurofibromatosis.Heterochromia iridum_item_0_0
  • Ocular melanosis – a condition characterized by increased pigmentation of the uveal tract, episclera, and anterior chamber angle.Heterochromia iridum_item_0_1
  • Oculodermal melanocytosis (nevus of Ota)Heterochromia iridum_item_0_2
  • 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.Heterochromia iridum_item_0_3
  • Sturge–Weber syndrome – a syndrome characterized by a port-wine stain nevus in the distribution of the trigeminal nerve, ipsilateral leptomeningeal angiomas with intracranial calcification and neurologic signs, and angioma of the choroid, often with secondary glaucoma.Heterochromia iridum_item_0_4

Abnormal iris lighter Heterochromia iridum_section_4

Heterochromia iridum_unordered_list_1

  • 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.Heterochromia iridum_item_1_5
  • Congenital Horner's syndrome – sometimes inherited, although usually acquiredHeterochromia iridum_item_1_6
  • Waardenburg syndrome – a syndrome in which heterochromia is expressed as a bilateral iris hypochromia in some cases. A Japanese review of 11 children with albinism found that the condition was present. All had sectoral/partial heterochromia.Heterochromia iridum_item_1_7
  • Piebaldism – similar to Waardenburg's syndrome, a rare disorder of melanocyte development characterized by a white forelock and multiple symmetrical hypopigmented or depigmented macules.Heterochromia iridum_item_1_8
  • 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.Heterochromia iridum_item_1_9
  • Incontinentia pigmentiHeterochromia iridum_item_1_10
  • Parry–Romberg syndromeHeterochromia iridum_item_1_11

Acquired heterochromia Heterochromia iridum_section_5

Acquired heterochromia is usually due to injury, inflammation, the use of certain eyedrops that damage the iris, or tumors. Heterochromia iridum_sentence_29

Abnormal iris darker Heterochromia iridum_section_6

Heterochromia iridum_unordered_list_2

  • Deposition of materialHeterochromia iridum_item_2_12
    • Siderosis – iron deposition within ocular tissues due to a penetrating injury and a retained iron-containing, intraocular foreign body.Heterochromia iridum_item_2_13
    • Hemosiderosis – long standing hyphema (blood in the anterior chamber) following blunt trauma to the eye may lead to iron deposition from blood productsHeterochromia iridum_item_2_14
  • 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.Heterochromia iridum_item_2_15
  • Neoplasm – Nevi and melanomatous tumors.Heterochromia iridum_item_2_16
  • Iridocorneal endothelium syndromeHeterochromia iridum_item_2_17
  • Iris ectropion syndromeHeterochromia iridum_item_2_18

Abnormal iris lighter Heterochromia iridum_section_7

Heterochromia iridum_unordered_list_3

  • 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 Fuchs has been estimated in various studies with results suggesting that there is more difficulty recognizing iris color changes in dark-eyed individuals.Heterochromia iridum_item_3_19
  • Acquired Horner's syndrome – usually acquired, as in neuroblastoma, although sometimes inherited.Heterochromia iridum_item_3_20
  • NeoplasmMelanomas can also be very lightly pigmented, and a lighter colored iris may be a rare manifestation of metastatic disease to the eye.Heterochromia iridum_item_3_21
  • Parry–Romberg syndrome – due to tissue loss.Heterochromia iridum_item_3_22

Heterochromia has also been observed in those with Duane syndrome. Heterochromia iridum_sentence_30

Heterochromia iridum_unordered_list_4

Central heterochromia Heterochromia iridum_section_8

Central heterochromia is an eye condition where there are two colors in the same iris; the central (pupillary) zone of the iris is a different color than the mid-peripheral (ciliary) zone, with the true iris color being the outer color. Heterochromia iridum_sentence_31

Central heterochromia appears to be prevalent in irises containing low amounts of melanin. Heterochromia iridum_sentence_32

History Heterochromia iridum_section_9

Heterochromia of the eye was described by Aristotle, who termed it heteroglaucos. Heterochromia iridum_sentence_33

Notable historical figures thought to have heterochromia include Anastasius the First, dubbed dikoros (Greek for 'having two irises'), and Alexander the Great, as noted by the historian Plutarch. Heterochromia iridum_sentence_34

In other animals Heterochromia iridum_section_10

See also: Odd-eyed cat Heterochromia iridum_sentence_35

Although infrequently seen in humans, complete heterochromia is more frequently observed in other species, where it almost always involves one blue eye. Heterochromia iridum_sentence_36

The blue eye occurs within a white spot, where melanin is absent from the skin and hair (see Leucism). Heterochromia iridum_sentence_37

These species include the cat, particularly breeds such as Turkish Van, Turkish Angora, Khao Manee and (rarely) Japanese Bobtail. Heterochromia iridum_sentence_38

These so-called odd-eyed cats are white, or mostly white, with one normal eye (copper, orange, yellow, green), and one blue eye. Heterochromia iridum_sentence_39

Among dogs, complete heterochromia is seen often in the Siberian Husky and few other breeds, usually Australian Shepherd and Catahoula Leopard Dog and rarely in Shih Tzu. Heterochromia iridum_sentence_40

Horses with complete heterochromia have one brown and one white, gray, or blue eye—complete heterochromia is more common in horses with pinto coloring. Heterochromia iridum_sentence_41

Complete heterochromia occurs also in cattle and even water buffalo. Heterochromia iridum_sentence_42

It can also be seen in ferrets with Waardenburg syndrome, although it can be very hard to tell at times as the eye color is often a midnight blue. Heterochromia iridum_sentence_43

Sectoral heterochromia, usually sectoral hypochromia, is often seen in dogs, specifically in breeds with merle coats. Heterochromia iridum_sentence_44

These breeds include the Australian Shepherd, Border Collie, Collie, Shetland Sheepdog, Welsh Corgi, Pyrenean Shepherd, Mudi, Beauceron, Catahoula Cur, Dunker, Great Dane, Dachshund and Chihuahua. Heterochromia iridum_sentence_45

It also occurs in certain breeds that do not carry the merle trait, such as the Siberian Husky and rarely, Shih Tzu. Heterochromia iridum_sentence_46

There are examples of cat breeds that have the condition such as Van cat. Heterochromia iridum_sentence_47

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Heterochromia iridum.