Moreover, melanin is found in the light-sensitive tissue of the retina of the eye which plays a role in normal vision.

The exact function of protein P is unknown, but it has been found that it is essential for the normal coloring of skin, eyes, and hair; and likely involved in melanin production.

This gene is mutated in Astyanax mexicanus, a Mexican fish which is characterized by a chronic albinism in cave-dwelling individuals.

[8][9] A mutation in the HERC2 gene adjacent to OCA2, affecting OCA2's expression in the human iris, is found common to nearly all people with blue eyes.

It has been hypothesized that all blue-eyed humans share a single common ancestor with whom the mutation originated.