Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) aniridia ?
    ### Response:
    Aniridia is an eye disorder characterized by a complete or partial absence of the colored part of the eye (the iris). These iris abnormalities may cause the pupils to be abnormal or misshapen. Aniridia can cause reduction in the sharpness of vision (visual acuity) and increased sensitivity to light (photophobia).
    