Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the symptoms of Glaucoma ?
    ### Response:
    Symptoms of Glaucoma  Glaucoma can develop in one or both eyes. The most common type of glaucoma, open-angle glaucoma, has no symptoms at first. It causes no pain, and vision seems normal. Without treatment, people with glaucoma will slowly lose their peripheral, or side vision.
    