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Get the facts you need to know to understand and manage your glaucoma diagnosis and treatment. In this Glaucoma Fast Facts video, David Richardson, MD (San Marino Eye) discusses "understanding glaucoma."
Glaucoma Fast Facts: Understanding Glaucoma - Supported by an educational grant from Santen.
Andrew Jackson (Glaucoma Research Foundation): Hello and welcome to another edition of Glaucoma Fast Facts. In this video, glaucoma specialist Dr. David Richardson will help us to understand glaucoma. So, Dr. Richardson, if I have been diagnosed with glaucoma what do I need to know?
David Richardson, MD (San Marino Eye): The first thing you need to know is that you should be grateful that you've been diagnosed. Now that you've been diagnosed, there are a number of things that you will need to be aware of. From what to expect in terms of interactions with your physician, testing, treatment modalities and then of course, what to expect long term.
Now, one of the things that many people fear when they're first diagnosed with glaucoma is that they might go blind. The good news is, that with diagnosis, especially early on, with treatment, regular follow-up and testing with your physician, it is very unlikely that you will go blind. 95% of people who have glaucoma do not go blind.
What can I expect of my physician visits? Well, when first diagnosed with glaucoma, depending on the type of glaucoma, you may actually need to return to see your physician on a weekly or monthly basis early on until a baseline is established. And there will be quite a few tests. If you get to the point, which most people do, of having a stable controlled glaucoma, then you'll probably be seeing your physician two to three times a year. And in some cases, just once a year.
Now, in terms of the testing that you would be expected to undergo in the examination, of course we check the vision, but we also check [eye] pressures. Now, the pressure measurement itself, can be performed in a variety of methods. Some of the methods use an air puff, some use a handheld device that has a tiny little plunger that can check the pressure without anesthesia. And then some of the devices require anesthetic. So, drops on the surface of the eye are followed by placement of a small instrument against the surface of the eye, which then measures the pressure.
Two other tests are quite critical in terms of regular follow-up of your glaucoma. One of those is visual field testing. In which case you will sit, usually in front of a, kind of a white bowl and see lights of varying intensities, varying in position in the bowl. And when you see the light you press a button. Usually it's a handheld controller. Now, more modern visual field devices may actually use a virtual reality headset. But the bottom line is it's testing what you are able to see in terms of your entire field of vision. Because one of the things that glaucoma does, is reduce your field of vision.
Another type of test that's commonly performed is what's called Optical Coherence Tomography, or OCT. This is essentially a scan of the eye. And of course, the examination with your doctor.
You will need, on initial examination, and then usually at least once yearly after that, you'll need two particular components. One is what's called Gonioscopy, which is an evaluation of the drainage structures in the eye, what we call the angle. That usually uses a contact lens exam. It's not painful. Anesthetic is provided and a lens is placed over the eye. And then of course, the dilated exam. This is an exam in which you will receive eyedrops and you'll generally need to wait between 20 and 40 minutes for the pupil to dilate so that your ophthalmologist can actually get a look inside of your eye.
Andrew Jackson: Why is intraocular pressure important in glaucoma? And how does vision loss occur in glaucoma?
David Richardson, MD: Intraocular pressure is important because it's the one thing that we can measure and control. Now, there is a range of normal intraocular pressure that is traditionally thought of as 12 mm Hg to about 22 mm Hg. Millimeters of mercury is just the unit of measurement of pressure in the eye. Now, given that it's the only thing that we really can measure that we can control, and the only thing that's been proven to actually be associated with glaucoma progression, it is a true vital sign of the eye.
Now, with high pressures and sometimes even normal pressures the optic nerve itself can be damaged by this high pressure. What we do know is that in those who are susceptible to glaucoma and sensitive to high pressures, that the vision itself is lost in a very subtle manner in the open angle form of glaucoma. So subtle in fact that you would not be expected to even be aware that it was occurring until the condition had actually become quite advanced.
Early on for most people, these subtle changes in vision tend to be out in the periphery of one's field. Now, the problem with that is that you're generally not aware of what you don't see. So just as we don't tend to be aware of the fact that we don't see things behind us. We just wouldn't be aware if we were losing our peripheral visual field until we started, say, bumping into doors. I often will tell my patients that it's similar to hearing. You're just not aware of what you don't hear. Then later on in glaucoma, you can actually end up with such restricted field of vision that it's really no longer safe to drive because you can't see what's to the left or the right of you. And then, in the worst cases of glaucoma, you actually have the field constrict and start to affect the center of your vision.
Andrew Jackson: Who is susceptible to glaucoma? Who gets glaucoma?
David Richardson, MD: Glaucoma can be experienced by anyone at any age, but there are age groups as well as certain races and those in certain geographic locations that are more likely to be susceptible to glaucoma. So for example, glaucoma tends to be seen early on in infancy or early childhood in what's called congenital glaucoma. It really doesn't start to become common at least the most common form of glaucoma, open angle glaucoma, until we reach our 40s. And so, it's really important for most people who are otherwise healthy and don't have any issues with their eyes, to be checked at least once around age 40. Now glaucoma becomes more and more common as we age. And so, as we age we also end up with other eye conditions such as dry eye, macular degeneration, things that would tend to bring somebody into an ophthalmologist’s office. So, there is often an opportunity to get checked for glaucoma at that time as well. Now, I mentioned race and geographic location. So, those who have an Asian, Latin, Latinx, or African heritage, they tend to have a higher risk of developing glaucoma.
Andrew Jackson: What causes glaucoma?
David Richardson, MD: That is a good question. If we had the full answer to that question things would be a lot easier for both patients and doctors. We don't really understand the underlying problem with glaucoma, but what we do know, for most people, is that it's a plumbing problem. So essentially fluid is produced inside the eye in the tissue called the ciliary body. That fluid bathes the internal structures of the eyes, providing nutrition and oxygen, and also removing waste products. That fluid which is called the aqueous fluid then leaves through what we call the angle. It's the drainage structure that includes the trabecular meshwork, which is a type of grating, that's a simple way to think of it. And then into Schlemm's canal and out of these collector channels. That's one of the ways that the fluid exits.
What happens in most forms of glaucoma is that there is some kind of blockage of the drainage system. What happens is that balance between production of fluid and exiting of fluid from the eye is disrupted. So you end up with fluid backing up and there being a higher pressure in the eye. There needs to be a certain amount of pressure in the eye just to keep it round and keep the structures functioning well. But if the pressure becomes too high it can cause damage to the tissue. But what we do know is that lowering the intraocular pressure is the one proven treatment for glaucoma to protect the vision of those who have this condition.
Andrew Jackson: Thank you for your time today, Dr. Richardson. And for more information, please visit our website, glaucoma.org and download our free 40 page booklet, "Understanding and Living with Glaucoma."
Last reviewed on October 22, 2020