As the name suggests, macular degeneration involves a degeneration of tissues under the retina. The most common form of macular degeneration is age-related macular degeneration, most prevalent in the population aged 60 and older. Age-related macular degeneration is also most prevalent in Caucasians. It is particularly detrimental to quality of life because it preferentially affects the central vision. For this same reason, its only saving grace is that it will never completely blind a person in that it spares the peripheral vision. With this peripheral vision a person can be reasonably expected to get around, although at its worst macular degeneration will take our ability to read, drive, use a computer, or even recognize faces.
Dry Macular Degeneration
There are two main categories of macular degeneration, dry and wet. Ninety percent of macular degeneration is the dry form which involves a degeneration of the tissues under the retina, and ultimately the retina itself. This form is the earlier and less aggressive form of the disease. It should be understood, however, that dry macular degeneration alone can result in extreme vision loss. The earliest component of dry macular degeneration is the accumulation of deposits, called drusen, under the retina. These drusen can be visible on retinal examination and their concentration and size correlate with the severity of the disease. More advanced forms of dry macular degeneration involve entire patches of degeneration in and under the retina, visible on examination as what is called geographic atrophy. As stated above, although still a dry form of macular degeneration, this can result in markedly reduced vision.
Dry macular degeneration cannot currently be reversed by medical intervention, but to a significant degree, its progression can be slowed or abated with a number of interventions. These include the regular use of eye vitamins which include the minerals and vitamins studied in the Age Related Eye Disease Study or AREDS. Use of these nutrients resulted in a 25% reduction of risk of progression to the wet form of macular degeneration. These components are: vitamin A (as beta-carotene), vitamin C, and vitamin E, as well as the minerals zinc and copper.
Another important intervention is cessation of smoking, which is an independent risk factor for the progression of macular degeneration to the wet or more aggressive form. Hypertension, or high blood pressure, is still another independent risk factor for the development of wet macular degeneration. Studies show less than half of Americans with hypertension have their blood pressure under control, and in practice this correlates directly with worsening macular degeneration in patients. There is almost never a reason that high blood pressure cannot be controlled, and most often it can be controlled by simply adjusting the dose of anti-hypertensive medications, resulting in a much better chance of maintenance of vision in age-related macular degeneration.
Aside from use of the AREDS supplements, cessation of smoking, and aggressive control of blood pressure, the following interventions may also reduce one’s risk of wet macular degeneration: avoidance of dietary fat and a diet rich in vegetables, particularly highly pigmented vegetables.
Wet Macular Degeneration
Wet macular degeneration is a more aggressive form of the disease and responsible for most of the vision loss associated with macular degeneration. Approximately ten percent of eyes suffering dry macular degeneration will progress to this more aggressive form. The disease mechanisms involved in wet macular degeneration involve the tissues adjacent to the retina and include increased inflammation, leakage of blood vessels, degeneration of vital tissues, and eventually the growth of new unhealthy blood vessels under the retina. These new blood vessels unfortunately develop most often beneath the macula, which is the part of the retina responsible for fine central vision. It is for this reason the typical vision loss in macular degeneration affects the central and not the peripheral vision. These new unhealthy blood vessels are prone to leakage of fluid and frank bleeding which can lead to scar tissue and further degeneration of the retina if untreated.
In past years, no good treatments for wet macular degeneration existed. Both patients and their retinal specialists could only watch in frustration as precious sight was lost permanently over time. Eventually hot lasers were used with some success, but often with residual vision loss caused by the laser as well as the disease. Photodynamic therapy, or cold laser, eventually allowed for less residual damage and served as an effective treatment for certain lesions. This cold laser, however, still left over half of treated eyes with a loss of vision over time.
In more recent years, steroids and newer medications including VEGF inhibitors have been used more successfully to limit both the leakage and growth of the unhealthy blood vessels developing in wet macular degeneration. Combinations of these and past treatments are being used with more success than previously could be offered to patients with macular degeneration. One of the newer classes of drugs is that called VEGF-inhibitors. Included in this group are the drugs avastin, lucentis, and Eylea which have allowed approximately 90% of macular degeneration patients, receiving early treatment, to maintain or gain vision. Many new treatments are in constant research, but no treatment can substitute for regular examination and early diagnosis.