heterochromia is a genetic anomaly which is characterized by the change in eye color of some mammals, causing each eye has a different color.
Also known as ocular heterochromia, this anomaly happens directly in the amount of melanin present in the iris, the tissue responsible for giving the color to the eyes.
Heterochromia is common mainly in cats and dogs, however it is estimated that six out of every thousand people also have some level of this genetic anomaly.
People who are born with heterochromia should undergo medical tests to rule out other congenital diseases related to anomaly in eye color.
When heterochromia presents itself only as a genetic alteration, people usually wear contact lenses to hide the changes in iris pigmentation.
Types of heterochromia
There are three main types of heterochromia: sectorial, central and complete.
Sectoral heterochromia
It is so called when the same iris has two different colors, one of which must be dominant.
central heterochromia
Also known as “cat's eye”, people with this type of heterochromia have two or more circles in the iris, of different color.
complete heterochromia
It is the rarest and most different type, as it consists of the complete difference between eye color. For example: when the right eye is blue and the left eye is brown.
Causes of heterochromia
Heterochromia can be congenital or acquired.
In case it is congenital, means that the individual was probably born with a genetic alteration that changed the hue of the iris. However, it may be that the differentiation between eye color may be the consequence of other congenital problems, such as Waardenburg Syndrome and the Horner's Syndrome.
In case the heterochromia is acquired, means that it arose from a disease acquired after birth, such as:
- Glaucoma;
- Iritis (inflammation of the iris);
- Bleeding from the irirs (caused by trauma);
- Melanoma in the iris;
- Neurofibrimatosis;
- Diabetes.