According to the World Health Organization, in a 2002 report, Glaucoma is the 2nd leading cause of blindness after Cataracts worldwide. In the United States, Glaucoma is the 2nd leading cause of blindness after Macular Degeneration, closely followed by Diabetic Retinopathy.
What does the average person need to know about Glaucoma? Lets talk about what we do and do not know about this sneaky disease that robs a person's vision by slowly and silently killing the OPTIC NERVE which sends vision signals from the eye to the brain.
First, what we know:
Science and clinical experience have provided us with an excellent ability to treat glaucoma and significantly reduce your risk of blindness from the disease if detected in time. We treat glaucoma with eye drops that lower the internal pressure of the eye. The better we control eye pressure, the more we protect the dying nerve and preserve a person's vision. We also have learned that the earlier we intervene with glaucoma, the easier it is to control or stop ongoing damage to the nerve. Glaucoma seems to have inertia. Advanced cases are reportedly more difficult to control--similar to putting the breaks on a freight train. That perception may be due to a reduced margin for error when glaucoma is at its end stage when there is very little nerve left to save. We do have patients we treat who came to us with very minimal nerve left and were dangerously near blindness, who have managed to keep their remaining vision with consistent treatment.
We know that there are several types of glaucoma. The primary types are those described in this post and are the most difficult to understand. There are several secondary types that happen when the pressure spikes due to anatomical problems, genetic defects, or injury.
What we don't know:
In the past, our view of glaucoma was rather simplistic. Too much pressure in the eye pinched the nerve and slowly strangled it to death. The pressure became elevated due to poor drainage or excessive production of the fluid that is constantly being exchanged in the front of the eye. While this certainly explains some glaucoma cases, there are many that don't fit this tidy scenario. For those of us that battle this disease daily, glaucoma is the Sneak-thief of sight. Sometimes it can look like you have glaucoma when you don't. Conversely, it can look like you don't when you do, and is often missed at Eye Exams. You can have high pressure and no glaucoma, or you can have normal pressure and have glaucoma. And if you have low pressure glaucoma, we treat by lowering the pressure (which is proven to help), but we don't know why it does. When you add to that the fact that you have to lose a significant percentage of your nerve (50-75%) before we can measure damage to your vision via Visual Field testing (one of the traditional keystones to diagnosis), you can begin to appreciate why diagnosing it can get so complicated. Theories abound, but why glaucoma actually happens is still a mystery.
So, the moment glaucoma starts in a patient, the majority of doctors will miss it. The moment you go blind from glaucoma, the majority of doctors will admit that you have it. And there is this large chasm between the two. In medicine, we love to be certain of our selves and our diagnoses which I think lends bias toward later diagnosis since glaucoma doesn't get obvious until its later stages.
Over the past few years, scientific study has helped us define some of the risk factors associated with the Primary glaucomas. In general, they are listed in order of importance:
- High pressure
- large Nerve cupping
- thin corneas
- Family History
- African, Asian, or Latin race (but all races affected)
- Severe Myopia (near sighted)
- systemic disease--high blood pressure, diabetes
- Sleep Apnea
- History of Migraines
Because glaucoma is an asymptomatic process, and because it doesn't become obvious until its end stages, there is a movement toward early diagnosis. We know that the earlier we diagnose this disease, the more uncertainty we have to live with, and the more we have to rely on the preponderance of risk factors. In medicine, we commonly treat based on risk factors (we lower cholesterol to reduce your chances of Heart Disease and Stroke, for example.) Thinking of glaucoma this way is a paradigm change from the days when we wanted to declare with absolute certainty that "you did or did not have glaucoma" when we finished up your eye exam.
Today, one of the most significant tools we have in our toolkit is the LASER. In our office, we use Ocular Coherence Tomography (OCT) by Humphries Ziess to measure the thickness of your Retinal nerves and track that thickness over time. Thinning nerve suggests glaucoma. We also use high resolution retinal photography over time, we measure your corneal thickness, and the gold-standard Visual field testing over time (which really doesn't tell us too much in the early stages of the disease). We combine the data we collect from these tests with what we know about your risk factors and make our decisions about treatment or followup.
With all the uncertainty about the origins of glaucoma and its early detection, we are very certain about treating the disease. Our goal is to lower the pressure in your eyes, and then monitor the health of your nerve as we keep your pressure down over time. Today's meds are effective and easier than ever. In most cases, one drop of medicine in your eyes each night does the trick. If today's first-line meds don't work, we may have to use additional drops, which may mean instilling drops 2 or 3 times a day. If drops don't work, then we use LASERs and surgery to reduce eye pressure. Effective eye-pressure control protects the health of your nerve and preserves your vision.