If you are like many persons that we have cared for, one of the first thoughts you have when presented with the knowledge that you have glaucoma is: will I be blind? The good news is that if you are not blind at this time, there is a very good chance that you will never be blind, at least from glaucoma. It is true that glaucoma is the second leading cause of blindness in the world after cataract. And, it presents a real threat to the vision of anyone who develops it. But from scientific studies all over the world and among persons just like you, we can say that the vast majority of persons who know that they have glaucoma, and who continue to follow the standard care instructions, will arrive at the end of their lives still reading and seeing well enough to enjoy life from both eyes.
Once we are adults, we don’t grow any new cells in our brain. Since glaucoma kills nerve cells that are truly part of the brain, it is not surprising that once vision is lost from glaucoma, it cannot be restored. The nerve cells that are dead were part of an intricate network in the retina and had a long fiber stretching inches up into the brain to begin a visual process that is more complex than we can even imagine now. Our best hope for the glaucoma patient, and the goal of treatment, is to save the vision that is left. We can do that to such an extent that most of those with glaucoma will live normal visual lives. Research in our laboratories and in others is presently working very hard to find ways to restore lost vision from glaucoma and other diseases (see section Can glaucoma be cured?), but at present nothing can be done to return vision that has been lost from glaucoma.
Actual statistics show that about 5% of European-derived persons with glaucoma will lose the ability to read standard print in both eyes from open angle glaucoma. The number is 3 times higher among African-Americans. And, it is also 2-3 times higher for those with angle closure glaucoma. But, many of this small percentage who become blind are those who were nearly blind before they found out that they had glaucoma. A famous glaucoma specialist from Boston, Morton Grant, wrote about his many years of seeing and studying glaucoma. He concluded that those few patients who did badly and lost their vision from glaucoma were most often those who didn’t follow care instructions or who came to the doctor too late. For the persons in that group, we have included a section What does low vision treatment have to offer?(see section What does low vision treatment have to offer?)
Again, looking at real statistics, about 15% of glaucoma patients will lose the ability to read in one eye. That is a tragedy for them and hurts their ability to do some things that require vision to see in 3 dimensions, called depth perception. Having lost one eye, one is more likely to knock over the salt shaker at dinner, or to stumble on stairs and curbs. Glaucoma damage decreases the contrast sensitivity of the vision system, so what seemed like a black and white page of print before is now more grey and white. Glare is more of a problem for the glaucoma patient. And, you must develop methods to adjust to changes in lighting when moving from bright sunshine to dark interiors, or the other way around. Each of these effects is due to the loss of some ganglion cells from the retina in the eye.
Glaucoma is most likely to affect one eye much more than the other. We don’t know why this is, since both eyes have seemingly been exposed to the same environment, diet and use. My mom went to the orthopedic surgeon with pain in her right knee. She asked the doctor: “why is my knee hurting?” and he answered: “Well, Mrs. Quigley you’re 80 years old.” She said: “The other knee’s 80, too, and it doesn’t hurt!” But, it turns out to be fortunate that glaucoma affects one eye more, since damage mostly in one eye with the other eye unaffected leaves the person pretty functionally normal. Our research at the Glaucoma Center of Excellence has been instrumental in showing how glaucoma affects persons’ lives in the real world. Those with one eye that is largely intact can do most daily activities as well as persons with two good eyes. While they must maintain a higher level of alertness, driving and walking are largely done just as well and safely by early and moderate glaucoma patients as their equal aged brothers and sisters with two good eyes.
The areas of vision affected by glaucoma are fortunately not in the center part of our world where we read and watch television and use computers. The zones where the early dying nerve cells see the environment are in the mid-peripheral area, not the center and not at the extreme outside of our vision. Since the brain normally gets input from both eyes about every place in our immediate world, as long as one eye is providing the picture of a zone, the brain isn’t missing anything. This explains something that puzzles patients when they see their visual field testing from each eye. The doctor shows them black areas (areas where the eye cannot see) in one eye, yet as far as the patient is concerned there are no such black areas or missing spots in their real world when they are looking with both eyes. That’s good for continuing to function normally, but it is one reason why people don’t notice their own glaucoma damage until very late in the injury process. If the left eye still sees what the right eye is missing, damage in the right eye is not noticed. And, the damage happens so slowly that the person has time to adjust to the change without realizing it is happening. When we measured those with severe glaucoma damage in both eyes on a walking course, the person bumped into things more and walked more slowly than those of the same age. When we asked them if they had any trouble walking, they said: “No”—because walking had become more difficult very gradually and they had taken it for granted that it was due to old age.
There is very active research to determine what effects glaucoma has on important activities of daily living. We often hear from patients that they are having more difficulty with reading, for example. When we measure their acuity on the letter chart on the wall, they have normal 20/20 vision. Perhaps the subtle loss of nerve cells near the central vision, or other effects of glaucoma, do actually impair reading. We have determined that glaucoma patients can start reading at a normal pace, but slow significantly within 15-20 minutes. Glaucoma patients also give up driving earlier than persons of the same age without vision problems. Driving a car is a vital personal activity that determines in many ways the ability to live independently in our society. We need to determine which patients should, in fact, stop driving, and which ones can continue to do so safely. If you are considering whether you are safe in continuing to drive and you have glaucoma damage to vision, consider having a formal driving test through a low vision service.
While it is true that most glaucoma patients don’t get to a stage of severe vision loss, there is a slow worsening of vision function in some glaucoma patients with time, even when appropriate treatment is given. This worsening is so minor in the majority that most will not be impaired in their lifetime. But, a minority of those with glaucoma progressively worsens at a rate much greater than the rest. For the slow progressors, standard treatment is perfectly sufficient, while for the rarer ones with more aggressive disease, treatment must also be aggressive. As we deal with the examining techniques and treatments for glaucoma in the next sections, it will become clearer that “one size doesn’t fit all” for glaucoma treatment. Some need only regular examinations and don’t even need pressure lowering therapy, while others must undergo surgery to save vision. But, whichever group one falls into, vision should be able to be saved with a good program jointly agreed to by doctor and patient.