Questions and Answers on Research and
Treatments for Age-Related
A Conversation with Dr. Hendrik P.N. Scholl
Question: Scientists often cite both the “bad news and the good news” about the state of our understanding of age-related macular degeneration (AMD). Could you elaborate?
Yes. We have reason to be concerned about the rising number of people with AMD due to an aging population, but also hopeful about the state of AMD research.
I'll start with the bad news. AMD, which is the leading cause of blindness in industrialized nations, presents extraordinary vision challenges for our country. The incidence of the disease will increase significantly in the years ahead, particularly with the aging of the Baby Boom generation. More than 11 million people in the United States have some form of AMD, and that number is expected to double to nearly 22 million by 2050.
For many, the loss of vision and diminished quality of life is a very real threat. AMD affects the macula, the central area of the retina that allows people to see the fine detail needed to do daily tasks. The disease can gradually destroy a person's central vision, resulting in an inability to read, drive, see faces, or conduct other activities of daily living. As we know, severe vision loss is associated with decreased independence and increased risks of depression.
But there is good news too. First, the Age-Related Eye Disease Study (AREDS) has found that taking a specific high-dose formula of antioxidant vitamins and zinc (called the AREDS formula) at certain stages of AMD may delay or prevent further vision loss.
Second, in the past decade there have been major advances in the treatment of the most severe form of AMD, known as wet AMD, and in our understanding of how dry AMD, the most common form of the disease, develops. These discoveries bring us closer to understanding how to prevent, detect, or treat the disease.
In recent congressional testimony, I quoted Dr. Francis Collins, Director of the National Institutes of Health, who said, “Twenty years ago, we could do little to prevent or treat AMD.” Today, he noted, because of research and new treatments, “1.3 million Americans at risk for severe vision loss over the next five years can receive potentially sight-saving therapies.”
You also stated, “Fifteen years ago, there was not a lot new in AMD research, but now it is one of the hottest areas.” How so?
The explosion of genetic research in the last two decades is one reason. In fact, one fourth of all genes discovered to date are associated with both common and rare eye diseases.
A recent breakthrough has been achieved by the AMD Gene Consortium, which has consolidated 15 international studies representing more than 17,000 patients worldwide. In a process known as gene mapping, the Consortium has identified 19 genomic loci-meaning the locations of genes or DNA strands on chromosomes-that are associated with AMD. This includes seven new loci. The Consortium also could identify five distinct biological pathways of disease mechanism, increasing our understanding of how the disease works. All of this could help researchers develop appropriate diagnoses and treatments.
What are other major areas of AMD research?
A number of scientists are looking at cell-based therapies as a possibility for regenerating or replacing certain eye cells. This may hold promise in replacing damaged eye cells with healthy ones and offer better treatment options for those AMD patients who have lost most of the photoreceptor cells in their macula.
Advances in imaging technology are also helping us better understand AMD. BrightFocus funding has allowed my own research team to study the structure of the central retina through high-resolution imaging, using new technologies such as optical coherence tomography (OCT). We then correlate these findings on structure with our findings on retinal function, using high-resolution functional mapping. This point-by-point comparison of structure and function within the central retina may offer us a better understanding of the disease, as well as improved monitoring tools to use in AMD treatments.
What are scientists uncovering about the role of the immune system in AMD?
Having genetic variants in certain genes that play a role in innate immunity has been strongly associated with a person's risk for developing AMD.
For example, here at Johns Hopkins we're involved in a multi-center collaboration with researchers at the University of California in San Diego and the Austrian Academy of Sciences in Vienna. This collaboration has produced an important finding on how the immune system can go out of control and cause age-related macular degeneration, due to a single mutation in the immune system protein known as complement factor H (CFH).
Normally, the body responds to stressors-such as invading germs, cigarette smoke, or too much sunlight-by turning on the immune system to flush out the toxins created by this so-called oxidative stress. CFH then “applies the brakes” to the typical inflammation response, keeping it under control. But our collaborating groups found that a single mutation in CFH destroys its protective abilities, which leads to out-of-control inflammation, drusen deposits (consisting of fats, proteins, pigments, and other waste products), and AMD. Discovering what goes wrong in the immune system could eventually lead to new treatments for the millions of people who suffer from this disease.
What about current treatments for AMD?
The treatment and prognosis for AMD depend on the type of AMD one has, and how advanced it is at the time of diagnosis.
Right now, we have treatments that rarely reverse the vision loss from AMD, but with early detection can help slow down its progression.
For wet AMD, we have the so-called angiogenesis inhibitors, typically injections into the eye (intravitreal) that are used to treat the disease. This includes EYLEA™ (aflibercept injection), Lucentis® (ranibizumab injection), and Avastin® (bevacizumab injection). The recent two-year CATT (Comparison of Age-related macular degeneration Treatment Trials) data have shown that intravitreal Avastin is not inferior to intravitreal Lucentis in the treatment of wet AMD. For both drugs, vision was slightly better with monthly rather than less frequent injections. You can read more about the study conclusions on the relative risks and benefits of these treatments, and what patients should discuss with their eye doctor, on the BrightFocus website.
For very advanced age-related macular degeneration, the Implantable Miniature Telescope (IMT) may help those with end-stage wet AMD gain back some useful central vision through magnification.
Research is under way on sustained release implants in the eye. These devices would offer the potential to reduce the frequency of doctor visits and eliminate the need for direct injections into the retina. Patients may only need to visit their doctor every four months, instead of every four to eight weeks.
Any advice you would offer those concerned about AMD?
If you are experiencing changes in your vision, see your eye doctor. Even if you are not having problems, be sure to get your eyes examined regularly so your doctor can monitor your vision.
We also need to push for increased federal and private funding of AMD research. If we are to meet the challenges ahead, more research must move forward.
* Dr. Scholl is the Dr. Frieda Derdeyn Bambas Professor of Ophthalmology at the Wilmer Eye Institute, Johns Hopkins University School of Medicine, in Baltimore, Maryland. This interview was conducted in May 2012.
Last Review: 05/14/13