Why does eye color vary among humans?
The color of the iris is determined by the amount and distribution of the pigment melanin, which is usually dark brown and is produced by a special type of cell called the melanocyte. In simple terms, a brown iris contains abundant melanin (more UV-protection), whereas a blue iris contains much less melanin. Albinos have an almost complete lack of melanin. This results in red or pink iris color, due to the greater visibility of blood vessels through the almost transparent iris. Hence, the eyes of albinos are extremely vulnerable to the sun’s UV-radiation.
