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Age-related macular degeneration (AMD), left untreated, is the leading cause of severe, permanent vision loss in Americans over 50. More than eight million people have earlier stages of AMD. This disease of the macula, the central and most sensitive part of the retina, can rob people of central vision. Left with only peripheral vision, they may struggle to identify faces, read books and watch TV, because they can see the side or peripheral vision, but not straight ahead.
About 90 percent of people with AMD have a "dry" or non-neovascular or non-“new vessel” form, which typically manifests collections of yellow debris in the center of the retina, called drusen, and often has no symptoms. However, it may slowly progress to a dry “atrophic” form associated with loss of central vision. Alternatively, the drusen may be associated with the production of growth factors which lead to the "wet" or neovascular form of the disease, when tiny new blood vessels can leak fluid or blood, causing distortion or blank spots in the central vision, accompanied by scar tissue which causes permanent loss of vision. This may cause loss of central vision within days or weeks. The wet form may strike those with the dry form at any time.
AMD: Dry Type
Patients who are affected have gradual loss of central vision due to the death of photoreceptor cells and their close associates; retinal pigmented epithelial (RPE) cells. Photoreceptors, the cells in the retina that actually "see" light, are essential for vision. RPE cells are like the nursemaids for photoreceptor cells and are necessary for photoreceptor survival and functioning. Death of either of these cell types leads to death of the other. The cell death occurs in the macula. This is unfortunate because the macula is the center portion of the retina that is responsible for reading and other complex visual tasks. Therefore, patients with AMD gradually lose their central vision, and with it the ability to drive and read. As bad as this may seem, it is a gradual process and is compatible with reasonable functioning for many years.
AMD: Wet Type
As the photoreceptor and RPE cells slowly degenerate, there is a tendency for blood vessels to grow from their normal location in the choroid into an abnormal location beneath the retina. This abnormal new blood vessel growth is called choroidal neovascularization (CNV). The abnormal blood vessels leak and bleed, resulting in sudden and severe loss of central vision. Only 10% of patients with AMD have the wet type, but it is responsible for 90% of all blindness resulting from AMD.
Wilmer ophthalmologists are leading experts in the study, diagnosis and treatment of AMD. Because AMD can be relentless in its assault on vision, early diagnosis is critical to begin monitoring for the wet form. Wilmer has led development of studies of automated analysis and detection of this earlier stage, as well as studies evaluating devices that may be used in the home to detect conversion of the drug to wet form before substantial vision loss has occurred, when treatment has the greatest chance to preserve vision.
While there is no cure, age-related macular degeneration treatments may prevent severe vision loss or slow the progression of the disease considerably. Several treatment options are available, including:
- Anti-vascular endothelial growth factor (anti-VEGF) medicines. These medications -- injected into the middle cavity of the eye during an in-office procedure – can cause regression of as well as block the development of new blood vessels and leakage from wet macular degeneration. This treatment, based on studies in the laboratory and clinic led by Wilmer physicians, has been a major change in the treatment of this condition; many patients have actually regained vision that was lost. The treatment may need to be repeated on follow-up visits. Published studies have shown that approximately 90% of patients treated at Wilmer for wet AMD no longer go blind.
- Dietary Supplements. A large study performed by the National Eye Institute of the National Institutes of Health, called AREDS -- Age-Related Eye Disease Study -- showed that for certain individuals, vitamins C, E, beta-carotene, zinc, and copper can decrease the risk of vision loss by reducing the risk of developing wet AMD in patients with drusen. A second study, AREDS2, showed that substituting lutein and zeaxanthin for beta-carotene likely results in similar results for use in people who are active cigarette smokers for whom beta-carotene could increase the risk of lung cancer.
- Low vision aids and rehabilitation. Devices that have special lenses or electronic systems that produce enlarged images of nearby objects. They may help people who have vision loss from AMD, especially in conjunction with guidance from professionals who combine such aids with visual rehabilitation techniques.
- Implantable Miniature Telescope: A tiny telescope that is implanted inside the eye to improve vision and quality of life for a very few selected individuals affected in both eyes with substantial loss from AMD who have not had cataract surgery in at least one eye. The treatment program involves four steps: 1) diagnosis, 2) candidate evaluation, 3) implantation in conjunction with cataract surgery, and 4) rehabilitation.