Eye color determination and changes

Friday, November 6th, 2009 at 6:11 pm Post in Eye Diseases

A child’s eye color is always inherited from its parents, even if the influences from each parent may not even. Eye colors include black, gray, green or other combinations.

Eye color is determined by the pigmentation in the iris. Brown eye color is used to be considered as “dominant” and blue being “recessive”. In fact, the eye color involves quite a few variations. It is neither the simple blend of parents’ eye colors, nor certain regular combinations. There are still some eye colors such as gray, hazel and other special combinations that are beyond clear scientific explanation.

One point is obvious that three genes in the body are responsible for eye color inheritance and determine the three most common colors: green, brown and blue. And each parent has two pairs of genes on each chromosome that affect the eye color of their children. Researchers are also focusing on DNA analysis to find out adults’ eye color.

A brown pigment named melanin develops as a baby ages, so that its eye color will darken. It has been revealed that a child’s eye color can be completely different from both of its parents. But children are always born with brown eyes if their parents both have brown eyes.

Some exceptions may happen during births. For example, some children have different colors in two eyes. This exceptional eye color condition is mostly caused by faulty developmental pigment transport. The underlying reasons for this disease may be local trauma in the womb, benign genetic disorder or inflammation of the iris.

Eye color does not stay unchanged lifelong. The eye’s iris controls the pupil size, which enlarges under dim light conditions and contracts under bright lighting. These pupil size changes may lead to slight eye color change. Eye color changes can be natural or signs of eye diseases.

Normal eye color changes relate to mainly two types of factors: emotion and aging. Extreme emotions such as angry and delight can change both pupil size and iris color. Some of Caucasian people are reported to have eye color changes as they age.

Diseases such as Fuch’s heterochromic iridocyclitis, Horner’s syndrome and pigmentary glaucoma can lead to harmful eye color changes.