Heterochromia iridis - two eyes are different in color

What is heterochromia iridis?

Heterochromia iridis is a condition in which the iris in one eye has a different color than the iris of the other eye. The iris is the tissue of the eye that surrounds the pupil and imparts a color, whether green, blue, brown, hazel, grey, or other, to the eye. Heterochromia iridis is to be differentiated from heterochromia (difference in color) iridium (within the iris of one eye).

Iris color is the result of the pigment that is present in the iris. Brown eyes have large amounts of melanin pigment deposits, and blue eyes have a lack of melanin. Although eye color is inherited, the inheritance pattern is complex, with interaction of more than one gene. These genes interact to provide the full constellation of colors. Other genes may determine the pattern and placement of pigment in the iris, thereby accounting for solid brown as opposed to rays of color. Normally, the two irises of an individual are of the same color. In heterochromia, the affected eye may be hyperpigmented (darker or hyperchromic) or hypopigmented (lighter or hypochromic). Eye color is determined primarily by the concentration and distribution of melanin within the iris tissues.

In anatomy, heterochromia (Greek: heteros ‘different’ + chroma ‘color’) is 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, or caused by genetic mosaicism, chimerism, disease, or injury.

How rare is heterochromia iridis?

Heterochromia can be present at birth (congenital) or acquired. The incidence of congenital heterochromia iridis is approximately six out of a 1,000, although in most of these cases, it is hardly noticeable and unassociated with any other abnormality.

Heterochromia iridis facts

Heterochromia iridis is an uncommon condition in which the two eyes are different in color.
Heterochromia iridis may be congenital (present at birth) or acquired.
Hereditary heterochromia iridis may be associated with other abnormalities of the eyes or body.
Acquired heterochromia is usually due to an eye disease.
If the condition is acquired, treatment may be directed at the underlying cause.
Colored contact lenses may be used for cosmetic results.
Most cases of heterochromia iridis are mild and do not have associated problems.

What are risk factors for heterochromia iridis?

Familial genetic abnormalities, ocular trauma, and inflammation are all risk factors for the development of heterochromia iridis. The use of prostaglandin analogue eye drops is a modifiable risk factor.