Glaucoma is the number one irreversible eye disease worldwide. Many people believe that glaucoma is incurable, but in reality these are two concepts. First, it is impossible to regain sight after glaucoma has caused blindness. Second, glaucoma is preventable and controllable. It is important for people to have this understanding of glaucoma. So, why is glaucoma the number one irreversible blindness-causing eye disease. Because this disease unknowingly destroys the most important tissue in our eyes, the optic nerve. With current science and technology, nerve regeneration is impossible to achieve. Therefore, it is very difficult to recover from glaucoma once it reaches an advanced stage. However, there are now many means to interrupt the progressive process of glaucoma. Therefore, although glaucoma is an irreversible blinding eye disease, it is preventable and controllable.