Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Diabetic Retinopathy ?
    ### Response:
    Blood vessels damaged from diabetic retinopathy can cause vision loss in two ways. Fragile, abnormal blood vessels can develop and leak blood into the center of the eye, blurring vision. This is proliferative retinopathy and is the fourth and most advanced stage of the disease.
    