There are certain words you don’t want to hear from a doctor. If it’s a dentist, maybe it’s that you need a root canal. If it’s an oncologist, cancer. From an eye doctor, blindness. A long list of conditions can cause blindness, but needing glasses or contact lenses is not one of them. Patients who have high glasses prescriptions often say to me, “I am legally blind without my glasses, right?” My response that they are not is often met with surprise. While you may see poorly without them, you are not blind. Blindness only occurs if we are unable to improve vision with corrective lenses like glasses or contact lenses because of an underlying medical problem. If you have a high prescription but are best corrected to 20/20, you are not blind. You have “perfect” vision.
I imagine many people, as judged by several of my family and friends’ perception of blindness, think that blindness means total blackness, like being in a pitch black room. Although this can happen, it is rare and referred to as “total” or “complete” blindness, and it is just one example of the different types and levels of blindness. Most blind people have “partial” blindness meaning their vision is limited but they can still perceive light. Some have central vision loss, while still others have peripheral vision loss. Legal blindness is a level of vision loss that has been legally defined to determine eligibility for benefits. For most states, that level is a minimum of 20/200 best corrected vision or a field of vision of 20 degrees or less. Generally speaking, blindness is a level of vision loss that makes it difficult to do everyday activities like operate a car safely, read regular sized print like this blog, and cook, but most still have some usable vision that allows them to see changes in light and large objects.
Diabetes is the clear cause of the most cases of blindness between the ages of 20 and 74 in the United States. However, for people over 60, age-related macular degeneration (AMD) takes over. Just as most of us know someone that has been diagnosed with cancer, the same is true with AMD for those age 60 and up. A diagnosis of AMD often brings fear of losing a driver’s and independence.
I am well aware of the fear people have of this diagnosis. When delivering the news, I often bring hope by discussing the statistics of the disease. First, as many of 11 million Americans have some form of AMD, but the vast majority live normal lives. Over 90% of people have “dry” AMD, where debris slowly builds up under the macula causing loss of photoreceptors and disruption of central vision. The good news is 90% of patients with dry AMD have adequate vision to maintain independence; only about 10% progress to severe vision loss or blindness. “Wet” AMD is less common, representing 10% of all AMD, but much more aggressive. In wet AMD, abnormal blood vessels under the macula leak blood or fluid. Loss of central vision can occur quickly. About 90% of patients with wet AMD have severe vision loss or blindness. For both dry and wet AMD, peripheral or side vision remains.
Second, we want to focus on the risk factors to slow the progression of the disease and not the ones out of our control. As the graph from the National Eye Institute illustrates (Figure 1), AMD largely affects whites of advancing age. Family history also plays a factor in how aggressive this progressive disease is. We cannot control our age, our ethnicity, or our genetics, we can control smoking, diet, blood pressure, cholesterol, and wearing sunglasses while outside. Certain eye vitamins have been shown to slow the progression of the disease in some.
Figure 1: AMD largely affects whites of advancing age (National Eye Institute)
Third, it is important to watch the progression of the disease carefully. The most frustrating characteristic about AMD is there is currently no treatment for the dry form. There are effective treatments for wet AMD, but early detection is critical. A simple in-office macular scan is the best way to detect wet AMD and we do them routinely.
February is age-related macular degeneration month. In a previous blog I talked about healthy aging and how medical advances have dramatically increased life expectancy in the last century. This is a good thing, but because of this, more people now suffer with diseases associated with advanced age like AMD. We should acknowledge the fear of blindness with this diagnosis, but live hopefully in the statistics that most don’t go blind. We also want to focus on what we can control to reduce the chances of it happening, including yearly preventative eye exams for anyone 60 and older, even if your vision is 20/20.