Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) choroideremia ?
    ### Response:
    Choroideremia is a condition characterized by progressive vision loss that mainly affects males. The first symptom of this condition is usually an impairment of night vision (night blindness), which can occur in early childhood. A progressive narrowing of the field of vision (tunnel vision) follows, as well as a decrease in the ability to see details (visual acuity).
    