Heterochromia iridis is a condition in which the iris in one eye has a different color than the iris of the other eye or shows different colours within the same 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.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.