Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Diabetic Retinopathy ?
    ### Response:
    Diabetic retinopathy is a complication of diabetes and a leading cause of blindness. It occurs when diabetes damages the tiny blood vessels inside the retina, the light-sensitive tissue at the back of the eye. A healthy retina is necessary for good vision. If you have diabetic retinopathy, at first you may notice no changes to your vision.
    