Age-related macular degeneration (AMD) is the major cause of severe vision loss in people over age 60. There is currently no cure, but in many cases the progression of the disease can be slowed or somewhat reversed.
What Is the Macula?
The macula is at the back of the eye, the bull’s eye center of the retina. It is the part of the eye that allows us to see fine details such as the numbers on a watch, the features on someone's face, or the amount of spices poured from a container. People with macular degeneration still retain peripheral vision, but lose the ability to see details.
Risk Factors for Macular Degeneration
- Age (over 50)
- Genetic factors
- Light iris color
- Family history
- Heart disease
- High blood pressure
- High cholesterol
Symptoms of Macular Degeneration
The first sign of macular degeneration may be the appearance of spots, called drusen, in your retina. You may notice some distortion in straight lines. The dotted lines down the center of the road, for instance, may seem crooked or the doorframe may appear warped. If you notice these changes in vision, or if colors look different to each eye, see your eye doctor promptly for an evaluation. Early detection is important for effective treatment.
The Two Forms of Macular Degeneration
- “Dry” (nonexudative or atrophic)
- “Wet” (exudative)
Approximately 85–90% of people with macular degeneration have the dry form.
Dry (non-exudative) AMD:
Drusen (spots) on the macula that are present for a long time may cause the macula to thin out and stop working, or atrophy. This is considered the dry form of AMD, and causes slow, progressive vision loss. There are no approved medical or surgical treatments to reverse dry AMD, but there are many low-vision tools that can assist with daily living.
Researchers with the Age-Related Eye Disease Study (AREDS) concluded that a specific cocktail of vitamins and minerals reduced the risk of the progression of the dry form of AMD to the wet (or advanced) form of AMD in some individuals. In 2006, a second study, called AREDS2 showed that removing beta-carotene from the formulation (which was shown to increase the risk of lung cancer in smokers) and replacing it with lutein and zeaxanthin was safe and effective. These AREDS supplements are available at most pharmacies.
People with dry macular degeneration in one eye may be able to function very well using the central vision from the other eye. Even in cases where dry AMD affects both eyes, enough peripheral vision is usually retained to be able to continue activities that don't require fine vision.
The dry form of AMD can change into the wet form, which is much more severe. It is very important that people with dry AMD monitor vision daily with an Amsler grid and report any changes to their eye doctor.
Wet (exudative) AMD:
In the wet form of AMD, abnormal blood vessels grow under the macula and leak fluid and blood. The abnormal vessels, called choroidal neovascularization, may also lift up the retina.
If diagnosed early enough, an injection in the eye (i.e., intravitreal) of an anti-vascular endothelial growth factor (ant-VEGF) can seal these vessels and slow vision loss or somewhat restore vision. Previous trials have shown that approximately 90–95% of patients maintained their vision with intravitreal injections and 33–40% of patients had an improvement in vision. Lucentis (ranibizumab), Eylea (aflibercept) and Avastin (bevacizumab) have been used successfully to treat this disease.
Newer drugs are being investigated to improve on these sight-saving treatments. New England Retina Associates is involved in clinical trials testing potentially more effective treatments.
Other treatments for wet AMD
Photodynamic therapy (PDT)
PDT employs a photosensitizing drug (a drug that is “activated” when exposed to light) called Visudyne (verteporfin) that is injected into the patient’s arm and circulates to the abnormal blood vessels. The doctor then focuses an extremely low-energy red laser beam through the pupil of the eye onto the leaky vessels, activating the drug, which destroys the abnormal vessels. The objective is to destroy the abnormal blood vessels while relatively preserving neighboring healthy blood vessels and tissue.
Focal laser treatment
Higher energy laser treatment to the areas of neovascularization does not improve vision, it merely stops further deterioration and does not work all the time. Successful treatment is in large part determined by how early the problem is treated and the location of the abnormal blood vessels. In some cases the abnormal blood vessels will stop growing and leaking for at least one year. It is quite possible, however, that additional abnormal blood vessels will grow elsewhere in the eye after laser surgery.
Possible future treatments
At New England Retina Associates, we are keeping up-to-date on the latest retinal treatments being developed and are actively involved in research trials that we believe hold the most promise for our patients. Here are some areas of research that are being developed, but as of yet do not have a proven clinical application in most cases of age-related macular degeneration.
Stem cell research
Stem cell therapy involves replacing dead or dying cells in the eye with brand new cells that are derived from undifferentiated biological cells (stem cells). These stem cells can be derived from several different sources including blood, fat (adipose) cells, skin, bone marrow, etc. Researchers are working on many technical aspects of stem cell therapy that will be critical for success, including: maturation of the cell line to the right specifications, functional incorporation of stem cells with the body’s own cells and preventing immunologic rejection of stem cells by the body.
This treatment involves replacing defective genes inside individual cells to fix the defect that caused them to malfunction. Delivery of genes to target sites is accomplished directly by putting vector agents (certain types of viruses) carrying the therapeutic genes to a target tissue. These therapeutic genes would be theoretically used to cause a variety of effects including killing abnormal cells, which are causing the loss of vision, or to cause proliferation of cells to replace damaged cells which normally do not proliferate, i.e., photoreceptor cells within the retina. There has been some success in treating a few retinal diseases with gene therapy. For example, in Leber’s Congenital Amaurosis (LCA), a rare inherited eye disease, researchers have been able to insert a missing gene (RPE65) into retinal pigment epithelium (RPE) cells – those cells that are needed to support retinal health. Age-related macular degeneration is a more complex disease when it comes to genetic dysfunction. There are several genes and also environmental factors that contribute to a person’s risk of getting macular degeneration. However, as scientific discovery grows and our knowledge of the disease improves, gene therapy offers promise for the long term treatment of conditions such as AMD.
Making an electronic (man-made) replacement for the retina or part of the retina (sometimes called a “bionic eye”) is no longer a concept exclusively for the pages of science fiction novels. There already exists a retinal prosthesis approved for a very advanced form of retinitis pigmentosa. These devices are currently only used in patients with profound vision loss (either barely seeing light or no perception of light at all).
For Further Information
- AAO: What Is Macular Degeneration?
- National Eye Institute: Facts About Age-Related Macular Degeneration
- National Eye Institute: What the AREDS Means for You
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Images on this page courtesy of The Retina Research Fund