Aniridia, which literally means "without iris," is an eye condition characterized by the absense of partial absence of the iris muscle tissue. The iris, which is a disk of muscle suspended behind the cornea and immediately in front of the lens, regulates the amount of light entering the eye by adjusting the size of the pupil. Because of the damage to the iris tissue in patients with aniridia, a greater than normal amount of light enters the eye, which results in visual impairment.