Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Glaucoma ?
    ### Response:
    Glaucoma is a group of diseases that can damage the eye's optic nerve and result in vision loss and blindness. The most common form of the disease is open-angle glaucoma. With early treatment, you can often protect your eyes against serious vision loss. (Watch the video to learn more about glaucoma.
    