Eye color

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Eye color is a polygenic trait and is determined by the amount and type of pigments in the eye's iris.[1][2] Humans and animals have many phenotypic variations in eye color.[3] In human eyes, these variations in color are attributed to varying ratios of eumelanin produced by melanocytes in the iris.[2] The brightly colored eyes of many bird species are largely determined by other pigments, such as pteridines, purines, and carotenoids.[4]

Three main elements within the iris contribute to its color: the melanin content of the iris pigment epithelium, the melanin content within the iris stroma, and the cellular density of the iris stroma.[5] In eyes of all colors, the iris pigment epithelium contains the black pigment, eumelanin.[2][5] Color variations among different irises are typically attributed to the melanin content within the iris stroma.[5] The density of cells within the stroma affects how much light is absorbed by the underlying pigment epithelium.[5] OCA2 gene polymorphism, close to proximal 5′ regulatory region, explains most human eye-color variation. [6]

Contents

[edit] Genetic determination of eye color

Eye colors can range from the most common color, brown, to the least common, green. Rare genetic mutations can even lead to unusual eye colors: black, red, or the appearance of "violet." Eye color is an inherited trait influenced by more than one gene.[7][8] These genes are being sought using associations to small changes in the genes themselves and in neighboring genes. These changes are known as single nucleotide polymorphisms or SNPs. The actual number of genes that contribute to eye color is currently unknown, but there are a few likely candidates. A study in 2009 found that it was possible to predict the color of eyes in Rotterdam with more than 90% accuracy for brown and blue, using just six SNPs (from six genes) [9]

The gene OCA2 (OMIM: 203200), when in a variant form the gene causes the pink eye color and hypopigmentation common in human albinism. (The name of the gene is derived from the disorder it causes, oculocutaneous albinism type II.) Different SNPs within OCA2 are strongly associated with blue and green eyes as well as variations in freckling, mole counts, hair and skin tone. The polymorphisms may be in an OCA2 regulatory sequence, where they may influence the expression of the gene product, which in turn affects pigmentation.[10] A specific mutation within the HERC2 gene, a gene that regulates OCA2 expression, is partly responsible for blue eyes.[11] Other genes implicated in eye color variation are: SLC24A4,[12] TYR.[12]

Blue eyes with a brown spot, green eyes and gray eyes are caused by an entirely different part of the genome. As Eiberg said: "The SNP rs12913832 [of the Herc2 gene] is found to be associated with the brown and blue eye color, but this single DNA variation cannot explain all the brown eye color variation from dark brown over hazel to blue eyes with brown spots."

[edit] Synopsis

Schematic representation of different eye colors resulting from different conditions in the iris.[13]

[edit] Classification of colors

The perception of color depends upon various factors. These are the same eyes; however, depending on the light and surrounding hues, the eye color can appear quite different.

Iris color can provide a large amount of information about an individual and a classification of various colors may be useful in documenting pathological changes or determining how a person may respond to various ocular pharmaceuticals.[14] Various classification systems have ranged from a basic "light" or "dark" description to detailed gradings employing photographic standards for comparison.[14] Others have attempted to set objective standards of color comparison.[15]

As the perception of color is dependent on viewing conditions (e.g. the amount and type of illumination, as well as the hue of the surrounding environment), so is the perception of eye color.[16]

Eye color exists on a continuum from the darkest shades of brown to the lightest shades of blue.[7] Seeing the need for a standardized classification system that was simple, yet detailed enough for research purposes, Seddon et al developed a graded one based on the predominant iris color and the amount of brown or yellow pigment present. There are 3 true colors in the eyes that determine the outward appearance; brown, yellow, and blue. How much of each color one has determines the appearance of the eye color. The color of the eyes in turn depends on how much of these colors are present. For example, green eyes have blue and some yellow , making them appear green. Brown eyes appear brown because most of the eye contains the brown color. The above is true for Homo sapiens; the iris color can vary in the animal world. Instead of blue in humans, autosomal recessive color in the species Corucia zebrata is black, whereas the autosomal dominant color is yellow-green.[17]

[edit] Changes in eye color throughout life

In caucasian populations, children are most commonly born with unpigmented (blue) eyes. As the child develops, Melanocytes, cells found within the iris of human eyes (as well as skin and hair follicles) slowly begin to produce Melanin. Because Melanocyte cells continually produce pigment, eye color in theory, can be changed.

Changes (lightening or darkening) of eye colors during puberty, early childhood, pregnancy, and sometimes after serious trauma (like Heterochromia), do represent cause for plausible argument to state that some eyes can or do change, based on chemical reactions and hormonal changes within the body.

Studies on Caucasian twins, both fraternal and identical, have shown that eye color over time can be subject to change, and major demelanization of the iris may also be genetically determined. Most eye color changes have been observed or reported as caucasians with "Hazel" eyes (Arch Ophthalmol).

[edit] Eye color chart (Martin-Schultz scale)

Carleton Coon created this chart by the Martin-Schultz scale often used in physical anthropology.

I. LIGHT EYES:

  • light – gray, blue, green.
  • light-mixed:

a) very light-mixed (blue with gray or green or green with gray), b) light-mixed (light or very light-mixed with small admixture of brown pigment). Eyes light and light mixed are in 16-12 in Martin scale.

II. MIXED EYES:

  • mixed – [12-6 in Martin scale] mixture of light eyes (blue, gray or green) with brown pigment when light and brown pigment are the same level. Some of mixed eyes are accept to light-pigment eyes.

III. DARK EYES:

  • dark-mixed - (hazel) [6-4 in Martin scale] brown with small admixture of light pigment.
  • dark – [4-1 in Martin scale] brown (light brown and dark brown) and very dark brown (black).


[edit] Amber

Human amber eyes displaying the yellow pigments.

Amber eyes are of a solid color and have a strong yellowish/golden and russet/coppery tint. This might be due to the deposition of the yellow pigment called "lipochrome" in the iris (which is also found in green and violet eyes).[18][19] Amber eyes should not be confused with hazel eyes; although hazel eyes may contain specks of amber or gold, they usually tend to comprise many other colors, including green, brown and orange. Also, hazel eyes may appear to shift in color and consist of flecks and ripples; while amber eyes are of a solid gold hue.

The eyes of some pigeons contain yellow fluorescing pigments known as pteridines.[20] The bright yellow eyes of the Great Horned Owl are thought to be due to the presence of the pteridine pigment xanthopterin within certain chromatophores (called xanthophores) located in the iris stroma.[21] In humans, yellowish specks or patches are thought to be due to the pigment lipofuscin, also known as lipochrome.[22]

[edit] Blue

A blue iris

Blue eyes contain low amounts of melanin within the iris stroma; longer wavelengths of light tend to be absorbed by the underlying iris pigment epithelium, and shorter wavelengths are reflected and undergo Rayleigh scattering.[5] The type of melanin present is eumelanin.[23] The inheritance pattern followed by blue eyes is considered similar to that of a recessive trait, however it is a polygenic trait (meaning that it is controlled by the interactions of several genes, not just one).[8] Eiberg and colleagues showed in a study published in Human Genetics that a mutation in the 86th intron of the HERC2 gene, which is hypothesized to interact with the OCA2 gene promoter, reduced expression of OCA2 with subsequent reduction in melanin production.[24] The authors concluded that the mutation may have arisen in a single individual in the Near East or around the Black Sea region 6,000-10,000 years ago during the neolithic revolution,[24] perhaps suggesting that all people with pure blue eyes are more closely related. However, blue eyes with brown spots around the pupil are not related to this mutation.[24]

Blue eyes are most common in Northern and Central Europe and to a lesser degree in Southern Europe and also North America,[25], they are also found in part of North Africa[26] West Asia and South Asia in particular the northern areas. A 2002 study found the prevalence of blue eye color among Caucasians in the United States to be 33.8 percent for those born from 1936 through 1951 compared with 57.4 percent for those born from 1899 through 1905.[8]

Blue eyes have become increasingly rare among U.S. children with only 1 out of every 6, or 16 percent of the United States population having blue eyes.[27][28] The plunge in the past few decades has taken place at a remarkable rate. A century ago, 80 percent of people married within their ethnic group. [29] In the 1930s, eugenicists used the disappearance of blue eyes as a rallying cry to support immigration restrictions. They went so far as to map the parts of the country with the highest and lowest percentage of blue-eyed people.

[edit] Brown

Dark Brown human iris
Light brown human iris

Brown eyes are predominant in humans[30] and, in many populations, it is (with few exceptions) the only iris color present.[31] It is less common in countries around the Baltic Sea and in Scandinavia.

In humans, brown eyes contain large amounts of melanin within the iris stroma, which serves to absorb light at both shorter and longer wavelengths. Brown eyes are the most common eye color, with over half of the world's population having them. They are also the most dominant eye color gene. Both ancient Egypt, the Greek empire, and the Roman empire possessed predominantly brown eyes, as did much of Western civilization and the discovery of the Americas by the (European) Spanish speaking empire. However in modern times we see some colored eyes for aesthetic purposes with green eyes being common and blue less common. [5][23] Very dark brown irises may appear at a glance to be black.[32][33]

[edit] Gray

A steel blue-gray eye
Gray eye under magnification, exhibiting small amounts of yellow

Gray eyes have less melanin than blue eyes,[citation needed] even though they are considered a darker shade of blue (like blue-green). Gray eyes are most common in European Russia, Finland and the Baltic States.[citation needed] Under magnification, gray eyes exhibit small amounts of yellow and brown color in the iris. Ultimately there are at least two things that could determine gray eye color. The first is the amount of melanin made. And the second is the density of the proteins in the stroma. [34]

A gray iris may indicate the presence of a uveitis. However, other visual signs make a uveitis obvious. Gray iris color, as well as blue, are at increased risk of uveal melanoma. [35]

Visually, gray eyes often tend to appear to change between the shades of blue, green and gray; this is because gray eyes are extremely light, as mentioned before. The color change for gray eyes is usually influenced by the lighting and the colors in the surroundings (such as clothes, makeup, etc.).

The Greek goddess Athena was renowned for having "owl-gray" or "sea-gray" eyes (in Greek, γλαυκῶπις – glaukōpis).[36]

[edit] Green

Light green eyes
Olive green eyes

Green eyes are the product of low to moderate amounts of melanin and probably represent the interaction of multiple variants within the OCA2 and in other genes, including perhaps the red-hair gene.[37] Green eyes are most common in Northern Europe and Central Europe.[38][39] It can sometimes be found in part of West Asia, South Asia and North Africa. [40] A study of Icelandic and Dutch adults found that green eyes are much more prevalent in women than in men.[41] Almost 92% of the population in Iceland has either green or blue eye color.[42]

Among White Americans, green eyes are most common among those of Celtic and Germanic ancestry, about 16 percent.[43]


[edit] Hazel

This eye shows a mixture of brown, green, and amber colors

Hazel eyes are due to a combination of a Rayleigh scattering and a more than moderate amount of melanin in the iris' anterior border layer.[22][5] Hazel eyes often appear to shift in color from a light brown to a medium golden-dark green. A number of studies using three-point scales have assigned "hazel" to be the medium-color between the lightest shade of blue and darkest shade of brown.[44][45][46][47][48][49][50] This can sometimes produce a multicolored iris, i.e., an eye that is light brown near the pupil and charcoal or amber/dark green on the outer part of the iris (and vice versa) when observed in sunlight. Hazel is commonly found in Europe, some regions of the Middle East, North America, parts of Central Asia and parts of South Asia.

Definitions of the eye color "hazel" vary: it is sometimes considered to be synonymous with light-brown and gold.[51][32][44][46][49][52][53][54][55] In North America, "hazel" is often used to describe eyes that appear to change color.

[edit] Red

The eyes of a person with albinism may appear red under certain lighting conditions due to the very low quantities of melanin. "True" red eyes also exist in albinistic and even some non-albinistic populations, but are very rare. Only about 20 cases of natural red eyes are recognized throughout the world.[56]

[edit] Violet

The appearance of "violet" eyes is thought to occur from the mixing of red and blue reflections.[57] Some albinos have eyes that appear violet.[58] Violet eyes are genetically similar to blue eyes,[citation needed] i.e., they are a reflection, pigment, or variant of blue (Violet (color)). Violet eyes are extremely rare; some people remain convinced that it is impossible to have violet colored eyes. Though a violet color is considered rather unique when discussing eye color, there is a very small number of people possessing this very rare coloring. However violet eyes are commonly found in a few remote and high altitude areas of northern Kashmir.[citation needed]

[edit] Medical implications

Those with lighter iris color have been found to have a higher prevalence of age-related macular degeneration (ARMD) than those with darker iris color;[48] lighter eye color is also associated with an increased risk of ARMD progression.[59] An increased risk of uveal melanoma has been found in those with blue, green or gray iris color.[60][61]

Eye color may also be symptomatic of disease. Aside from the iris, yellowing of the whites of the eyes is associated with jaundice and symptomatic of liver disease, including cirrhosis, hepatitis and malaria.

[edit] Anomalous conditions

Aniridia: Eyes wherein the irises are not present; the eyes appear to be two large pupils.

[edit] Aniridia

Main article: Aniridia

Aniridia is a congenital condition characterized by an extremely underdeveloped iris which appears absent on superficial examination.[62]

[edit] Ocular albinism and eye color

Normally, there is a thick layer of melanin on the back of the iris. Even people with the lightest blue eyes, with no melanin on the front of the iris at all, have dark brown coloration on the back of it, to prevent light from scattering around inside the eye. In those with milder forms of albinism, the color of the irises is typically blue, but can vary from blue to brown. In severe forms of albinism, there is no pigment on the back of the iris, and light from inside the eye can pass through the iris to the front. In these cases, the only color seen is the red from the hemoglobin of the blood in the capillaries of the iris. Such albinos have pink eyes, as do albino rabbits, mice, or any other animal with total lack of melanin. Transillumination defects can almost always be observed during an eye examination due to lack of iridial pigmentation.[63] The ocular albino also lacks normal amounts of melanin in the retina as well, which allows more light than normal to reflect off the retina and out of the eye. Because of this, the pupillary reflex is much brighter in the albino, and this can increase the red eye effect in photographs.

[edit] Heterochromia

An example of complete heterochromia. The subject has one brown and one hazel eye. The subject also appears to have a faint star pattern in the hazel iris.
An example of sectoral heterochromia. The subject has a blue iris with a brown section.
Main article: Heterochromia

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 iris (complete heterochromia), or where the 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.[64] This uncommon condition usually results due to uneven melanin content. A number of causes are responsible, including genetics such as chimerism, Horners Syndrome and Waardenburg syndrome. A common cause in females with heterochromia is X-inactivation, which can result in a number of heterochromatic traits, such as calico cats. Trauma and certain medications, such as some prostaglandin analogues can also cause increased or decreased pigmentation in one eye. On occasion, the condition of having two different colored eyes is caused by blood staining the iris after sustaining injury.

[edit] Eye color change

Often, newborns have blue eyes, which change to green, hazel, light brown or dark brown. This is possibly the origin of the idiom "being blue-eyed" (i.e. naïve; gullible) or having "baby blues", or striking blue eye color.

It is thought that exposure to light after birth triggers the production of melanin in the iris of the eye. By three years of age, the eyes produce and store enough melanin to indicate their natural shade. While changes in eye color of infants are more common, even in adults, eye color changes are seen, most often as a result of exposure to the sun. Sunlight triggers melanin production in the eye, as it does to the skin.

Eyedrops containing a prostaglandin analogue (such as latanoprost) may result in a permanently darkened iris; these eyedrops are commonly used to treat open-angle glaucoma.[65]

[edit] References

  1. ^ 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.
  2. ^ a b c 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.
  3. ^ Morris, PJ. "Phenotypes and Genotypes for human eye colors." Athro Limited website. Retrieved May 10, 2006.
  4. ^ Oliphant LW. "Pteridines and purines as major pigments of the avian iris." Pigment Cell Res. 1987; 1(2):129-31. PMID 3507666.
  5. ^ a b c d e f g Huiqiong Wang, Stephen Lin, Xiaopei Liu, Sing Bing Kang. "Separating Reflections in Human Iris Images for Illumination Estimation." Proc. IEEE International Conference on Computer Vision, 2005.
  6. ^ http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1785344
  7. ^ a b Sturm RA, Frudakis TN. "Eye color: portals into pigmentation genes and ancestry." Trends Genet. 2004 Aug; 20(8):327-32. PMID: 15262401.
  8. ^ a b c Grant MD, Lauderdale DS. "Cohort effects in a genetically determined trait: eye color among US whites." Ann Hum Biol. 2002 Nov-Dec; 29(6):657-66. PMID 12573082.
  9. ^ "DNA test for eye colour could help fight crime", New Scientist 14 March, 2009. "Eye color and the prediction of complex phenotypes from genotypes" by Fan Liu et al., Current Biology Volume 19, Issue 5, 10 March 2009, Pages R192-R193.
  10. ^ Duffy DL, Montgomery GW, Chen W, Zhao ZZ, Le L, James MR, Hayward NK, Martin NG, and Sturm, RA "A Three–Single-Nucleotide Polymorphism Haplotype in Intron 1 of OCA2 Explains Most Human Eye-color Variation" Am. J. Hum. Genet. 2002 80:000, 2007.
  11. ^ Kayser M, Liu F, Janssens AC, Rivadeneira F, Lao O, van Duijn K, Vermeulen M, Arp P, Jhamai MM, van Ijcken WF, den Dunnen JT, Heath S, Zelenika D, Despriet DD, Klaver CC, Vingerling JR, de Jong PT, Hofman A, Aulchenko YS, Uitterlinden AG, Oostra BA, van Duijn CM. "Am J Hum Genet." 2008 Feb; 82(2):411-23.
  12. ^ a b Sulem P, Gudbjartsson DF, Stacey SN, Helgason A, Rafnar T, Magnusson KP, Manolescu A, Karason A, Palsson A, Thorleifsson G, Jakobsdottir M, Steinberg S, Pálsson S, Jonasson F, Sigurgeirsson B, Thorisdottir K, Ragnarsson R, Benediktsdottir KR, Aben KK, Kiemeney LA, Olafsson JH, Gulcher J, Kong A, Thorsteinsdottir U, Stefansson K. "Nature Genetics" 2007 Dec; 39(12):1443-52.PMID: 17952075
  13. ^ What Color Will My Baby’s Eyes Be?
  14. ^ a b German EJ, Hurst MA, Wood D, Gilchrist J. "A novel system for the objective classification of iris color and its correlation with response to 1% tropicamide." Ophthalmic Physiol Opt. 1998 Mar; 18(2):103-10. PMID 9692029.
  15. ^ Fan S, Dyer CR, Hubbard L. Quantification and Correction of Iris Color." Technical report 1495, University of Wisconsin-Madison, Dec, 2003.
  16. ^ Color Perception
  17. ^ Jones, S.L., Schnirel, B.L., Subspecies comparison of the Genus: Corucia, Leeway Corucia Research Center - LCRC, Polyphemos, {2006} Volume 4, Issue 1. pp. 1-25.
  18. ^ Howard Hughes Medical Institute: Ask A Scientist
  19. ^ Eye Color
  20. ^ Oliphant LW. "Observations on the pigmentation of the pigeon iris." Pigment Cell Res. 1987; 1(3):202-8. PMID 3508278.
  21. ^ Oliphant LW. "Crystalline pteridines in the stromal pigment cells of the iris of the great horned owl." Cell Tissue Res. 1981; 217(2):387-95. PMID 7237534.
  22. ^ a b Lefohn, A., Budge, B., Shirley, P., Caruso, R., and Reinhard, E. 2003. An Ocularist's Approach to Human Iris Synthesis. IEEE Comput. Graph. Appl. 23, 6 (November 2003), 70-75. DOI= http://dx.doi.org/10.1109/MCG.2003.1242384
  23. ^ a b Menon IA, Basu PK, Persad S, Avaria M, Felix CC, Kalyanaraman B. "Is there any difference in the photobiological properties of melanins isolated from human blue and brown eyes?" Br J Ophthalmol. 1987 Jul; 71(7):549-52. PMID 2820463.
  24. ^ a b c Eiberg H, Troelsen J, Nielsen M, Mikkelsen A, Mengel-From J, Kjaer KW, Hansen L. "Blue eye colour in human beings may be caused by a perfectly associated founder mutation in a regulatory element located within the HERC2 gene inhibiting OCA2 expression" Human Genetics January 3, 2008. PMID 18172690
  25. ^ Pigmentation, the Pilous System, and Morphology of the Soft Parts
  26. ^ http://en.wikiquote.org/wiki/Berber_people
  27. ^ Don't it make my blue eyes brown
  28. ^ [1]
  29. ^ Blue eyes are increasingly rare in America
  30. ^ Eiberg H, Mohr J. "Assignment of genes coding for brown eye color (BEY2) and brown hair color (HCL3) on chromosome 15q." Eur J Hum Genet. 1996;4(4):237-41. PMID 8875191.
  31. ^ http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=227220 OMIM - SKIN/HAIR/EYE PIGMENTATION, VARIATION IN, 1; SHEP1
  32. ^ a b Hammond BR Jr, Fuld K, Snodderly DM. "Iris color and macular pigment optical density." Exp Eye Res. 1996 Mar; 62(3):293-7. PMID 8690039.
  33. ^ Prieto JG. "Eye color in skin cancer." Int J Dermatol. 1977 Jun; 16(5):406-7. PMID 873674.
  34. ^ [2]
  35. ^ Stang A, Ahrens W, Anastassiou G,Jöckel KH. "Phenotypical characteristics, lifestyle, social class and uveal melanoma." 2003 December
  36. ^ The Perseus Digital Library: Homeric Hymns
  37. ^ Eye Color Explained
  38. ^ Although http://www.eyedoctorguide.com/eye_general/eye_color.html Blue Eyes Versus Brown Eyes: A Primer on Eye Color - EyeDoctorGuide.com ]
  39. ^ [http://cogweb.ucla.edu/ep/Frost_06.html Why Do Europeans Have So Many Hair and Eye Colors? ]
  40. ^ http://en.wikiquote.org/wiki/Berber_people
  41. ^ http://evoandproud.blogspot.com/2007/11/sex-linkage-of-human-skin-hair-and-eye.html
  42. ^ http://www.ncbi.nlm.nih.gov/pubmed/15226032
  43. ^ http://www.gnxp.com/blog/2008/12/nlsy-blogging-eye-and-hair-color-of.php
  44. ^ a b Zhu G, Evans DM, Duffy DL, Montgomery GW, Medland SE, Gillespie NA, Ewen KR, Jewell M, Liew YW, Hayward NK, Sturm RA, Trent JM, Martin NG. "A genome scan for eye color in 502 twin families: most variation is due to a QTL on chromosome 15q." 1: Twin Res. 2004 Apr; 7(2):197-210. PMID 15169604.
  45. ^ Albert DM, Green WR, Zimbric ML, Lo C, Gangnon RE, Hope KL, Gleiser J. "Iris melanocyte numbers in Asian, African American, and Caucasian irides." Trans Am Ophthalmol Soc. 2003; 101:217-21; discussion 221-2. PMID 14971580.
  46. ^ a b Mitchell R, Rochtchina E, Lee A, Wang JJ, Mitchell P; Blue Mountains Eye Study. "Iris color and intraocular pressure: the Blue Mountains Eye Study." Am J Ophthalmol. 2003 Mar; 135(3):384-6. PMID 12614760.
  47. ^ Lindsey JD, Jones HL, Hewitt EG, Angert M, Weinreb RN. "Induction of tyrosinase gene transcription in human iris organ cultures exposed to latanoprost." Arch Ophthalmol. 2001 Jun; 119(6):853-60. PMID 11405836.
  48. ^ a b Frank RN, Puklin JE, Stock C, Canter LA. "Race, iris color, and age-related macular degeneration." Trans Am Ophthalmol Soc. 2000; 98:109-15; discussion 115-7. PMID 11190014.
  49. ^ a b Regan S, Judge HE, Gragoudas ES, Egan KM. "Iris color as a prognostic factor in ocular melanoma." Arch Ophthalmol. 1999 Jun; 117(6):811-4. PMID 10369595.
  50. ^ Hawkins TA, Stewart WC, McMillan TA, Gwynn DR. "Analysis of diode, argon, and Nd: YAG peripheral iridectomy in cadaver eyes." Doc Ophthalmol. 1994; 87(4):367-76. PMID 7851220.
  51. ^ Understanding Genetics: Human Health and the Genome
  52. ^ Naldi L, Altieri A, Imberti GL, Giordano L, Gallus S, La Vecchia C; Oncology Study Group of the Italian Group for Epidemiologic Research in Dermatology (GISED). "Cutaneous malignant melanoma in women. Phenotypic characteristics, sun exposure, and hormonal factors: a case-control study from Italy." Ann Epidemiol. 2005 Aug; 15(7):545-50. PMID 16029848.
  53. ^ April Holladay. "Funny — you can't hide those lightening eyes." USATODAY.com. October 8, 2004. Retrieved September 17, 2006.
  54. ^ English JS, Swerdlow AJ, MacKie RM, O'Doherty CJ, Hunter JA, Clark J, Hole DJ. "Relation between phenotype and banal melanocytic naevi." Br Med J (Clin Res Ed). January 17, 1987; 294(6565):152-4. PMID 3109545.
  55. ^ Hara T. "[Increased iris pigmentation after use of latanoprost in Japanese brown eyes.]" Nippon Ganka Gakkai Zasshi. 2001 May; 105(5):314-21. PMID 11406947.
  56. ^ NOAH — What is Albinism?
  57. ^ BBC - h2g2 - Determination of Eye Color
  58. ^ http://farm1.static.flickr.com/206/463760280_9f62450fa3.jpg
  59. ^ Nicolas CM, Robman LD, Tikellis G, Dimitrov PN, Dowrick A, Guymer RH, McCarty CA. "Iris colour, ethnic origin and progression of age-related macular degeneration." Clin Experiment Ophthalmol. 2003 Dec; 31(6):465-9. PMID 14641151.
  60. ^ Stang A, Ahrens W, Anastassiou G, Jockel KH. "Phenotypical characteristics, lifestyle, social class and uveal melanoma." Ophthalmic Epidemiol. 2003 Dec;10(5):293-302. PMID 14566630.
  61. ^ Risk factors for malignant melanoma in an Icelandi...[Prev Med. 2004] - PubMed Result
  62. ^ eMedicine - Aniridia: Article by Daljit Singh
  63. ^ eMedicine - Ocular Manifestations of Albinism: Article by Mohammed O Peracha, MD
  64. ^ 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.
  65. ^ Hejkal TW, Camras CB (1999). "Prostaglandin analogs in the treatment of glaucoma". Seminars in ophthalmology 14 (3): 114–23. doi:10.3109/08820539909061464. PMID 10790575. 

[edit] See also

[edit] External links

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