Glaucoma is a relatively common disease, but most people don’t really understand what glaucoma is. We generally think of glaucoma having to do with high pressure in the eyeball. Just like everybody has a blood pressure, the pressure inside the artery system, everybody has a pressure inside their eyeballs too. The eye pressure doesn’t exactly correlate with blood pressure. While it is true that glaucoma has to do with high pressure in the eye, what is “high” for one person may not be high for another. That is because there are many factors that go into glaucoma, including things like family history, but high eye pressure is the only risk factor for glaucoma that we can change. In glaucoma, a patient has damage to the optic nerve, and we believe that lowering the eye pressure so it is not “high” for that patient will stop the glaucoma from getting worse. Some portion of this damage to the optic nerve is visible on exam, though sometimes it is difficult to tell on exam. That is why we rely on other tests, including the visual field test, where we check “side vision” because glaucoma causes people to lose their “side vision.” Ultimately, understanding and treating glaucoma is a complicated process, but the general rule that we use to help our patients is to keep the eye pressure low enough that the patient will not lose side vision.