Age-related macular degeneration, often called AMD or ARMD, is the leading cause of vision loss and blindness among Americans who are age 65 and older. Because people in this group represent an increasingly larger percentage of the general population, vision loss from macular degeneration is a growing problem.
AMD is degeneration of the macula, which is the part of the retina responsible for the sharp, central vision needed to read or drive. Because the macula primarily is affected in AMD, central vision loss may occur.
About 1.75 million U.S. residents currently have advanced age-related macular degeneration with associated vision loss, with that number expected to grow to almost 3 million by 2020.*
Wet and Dry Forms of Macular Degeneration
Macular degeneration is diagnosed as either dry (non-neovascular) or wet (neovascular). Neovascular refers to growth of new blood vessels in an area, such as the macula, where they are not supposed to be.
The dry form is more common than the wet form, with about 85 to 90 percent of AMD patients diagnosed with dry AMD. The wet form of the disease usually leads to more serious vision loss.
Dry Macular Degeneration (non-neovascular). Dry AMD is an early stage of the disease and may result from the aging and thinning of macular tissues, depositing of pigment in the macula or a combination of the two processes.
Macular degeneration mainly affects central vision, causing “blind spots” directly ahead.
Dry macular degeneration is diagnosed when yellowish spots known as drusen begin to accumulate in and around the macula. It is believed these spots are deposits or debris from deteriorating tissue.
Gradual central vision loss may occur with dry macular degeneration but usually is not nearly as severe as wet AMD symptoms. However, dry AMD through a period of years slowly can progress to late-stage geographic atrophy (GA) — gradual degradation of retinal cells that also can cause severe vision loss.
No FDA-approved treatments are available for dry macular degeneration, although a few now are in clinical trials.
A major National Eye Institute study (AREDS) has produced strong evidence that certain nutrients such as beta carotene (vitamin A) and vitamins C and E may help prevent or slow progression of dry macular degeneration. These findings have led to development of a number of different AREDS nutritional formulas for macular degeneration prevention.
The AREDS study shows that taking high dose formulas of certain nutritional supplements found in eye vitamins may reduce risk of early stage AMD progression by 25 percent.
Eye doctors also recommend that dry AMD patients wear sunglasses with UV protection against potentially harmful effects of the sun.
Wet Macular Degeneration (neovascular). In about 10 percent of cases, dry AMD progresses to the more advanced and damaging form of the eye disease.With wet macular degeneration, new blood vessels grow beneath the retina and leak blood and fluid. This leakage causes permanent damage to light-sensitive retinal cells, which die off and create blind spots in central vision.
Choroidal neovascularization (CNV), the underlying process causing wet AMD and abnormal blood vessel growth, is the body’s misguided way of attempting to create a new network of blood vessels to supply more nutrients and oxygen to the eye’s retina. Instead, the process creates scarring, leading to sometimes severe central vision loss.
Wet macular degeneration falls into two categories:
- Occult. New blood vessel growth beneath the retina is not as pronounced, and leakage is less evident in the occult CNV form of wet macular degeneration, which typically produces less severe vision loss.
- Classic. When blood vessel growth and scarring have very clear, delineated outlines observed beneath the retina, this type of wet AMD is known as classic CNV, usually producing more severe vision loss.
How Macular Degeneration Is Treated
There is as yet no outright cure for age-related macular degeneration, but some treatments may delay its progression or even improve vision.
Treatments for macular degeneration depend on whether the disease is in its early-stage, dry form or in the more advanced, wet form that can lead to serious vision loss. No FDA-approved treatments exist yet for dry macular degeneration, although nutritional intervention may help prevent its progression to the wet form.
For wet AMD, treatments aimed at stopping abnormal blood vessel growth include FDA-approved drugs of Lucentis, Macugen and Visudyne used with Photodynamic Therapy or PDT. Lucentis has been shown to improve vision in a significant number of people with macular degeneration.
Nutrition and Macular Degeneration
Many researchers and eye care practitioners believe that certain nutrients — zinc, lutein, zeaxanthin and vitamins A, C and E — help lower the risk for AMD or slow down the progression of dry macular degeneration. Benefits of high levels of antioxidants and zinc for halting or slowing development of macular degeneration have been widely reported based on results released in 2001 from the Age-Related Eye Disease Study (AREDS) conducted by the National Eye Institute.
Phase two of the AREDS study began in late 2005 to evaluate whether similar protective effects against AMD might be associated with other nutrients such as omega-3 fatty acids or “good fats,” and lutein and zeaxanthin found in green, leafy vegetables.
Archives of Ophthalmology reported findings in August 2001 that consumption of omega-3 fatty acids, which are particularly prevalent in cold-water fish, also had a protective effect against advanced macular degeneration. Meanwhile, consumption of omega-6 fatty acids, prevalent in vegetable oils, was associated with an increased risk of developing AMD.