Ask an Expert about Macular Degeneration

Researchers continue to explore environmental, genetic and dietary factors that may contribute to developing AMD. New treatment strategies are also being explored, including retinal cell transplants, drugs to prevent or slow down the progress of the disease, radiation therapy, gene therapies, a computer chip implanted in the retina (may help simulate vision) and agents to prevent the growth of new blood vessels under the macula.

The National Eye Institute’s Age-Related Eye Disease Study (AREDS) found that taking a specific high dose formula of antioxidants and zinc (500 milligrams of vitamin C, 400 International Units of vitamin E, 15 milligrams of beta-carotene, 80 milligrams of zinc as zinc oxide and two milligrams of copper as cupric oxide) may delay or prevent intermediate AMD from progressing to the advanced stage. There is no evidence, however, that the AREDS formula benefits people with early stage AMD. Patients with intermediate AMD in one or both eyes or advanced AMD (dry or wet) in one eye but not the other eye should consider taking the formula. Consult a physician before taking any supplements because they may be contraindicated for certain medical conditions or may react negatively with some medications.

The word edema refers to swelling from excessive accumulation of fluid in a tissue, and was formerly called hydropsy or dropsy. As such, by "macular dropsy,” you are likely referring to what is now commonly called macular edema, which is swelling in the center or the retina (the region known as the macula) caused by fluid leakage. The accumulation of fluid in the macular region can lead to a number of problems including blurred or distorted vision.

You are correct; Stargardt's disease is a rare form of juvenile macular degeneration. And unfortunately, there is no treatment or cure for the disease at present. There is a great deal of research into ways to prevent or treat Stargardt's disease; however, most of the studies conducted to date have centered on the following:

1. Genetic testing to identify the genes likely involved in the development of the disease
2. Development of better imaging strategies to diagnose and track progression of the disease
3. Testing of new treatment and prevention strategies in animal models of the disease

While much information has been gained and the data is promising, much still remains to be learned. There have also been several clinical trials at various levels involving human patients with Stargardt's disease. If you visit "clinicaltrials.gov" you can find up-to-date information regarding government-sponsored clinical trials that are either recently completed or presently underway. Also, if you type the following link into the address bar on your web browser, it will take you directly to a page on that site with links to information related to studies on Stargardt's disease: http://clinicaltrials.gov/ct2/results?term=stargardt

There are two forms of AMD: dry and wet. It is possible for a person to suffer from both forms, for AMD to affect one or both eyes, and for the disease to progress slowly or rapidly. Dry AMD may advance and cause loss of vision without turning into the wet form of the disease. However, it is also possible for early-stage dry AMD to change into the wet form of the disease.

Dry macular degeneration is the most common type of AMD. This form, in which the photosensitive cells of the macula slowly break down, is diagnosed in 85-90 percent of cases. Yellow deposits called drusen (extracellular waste products from metabolism) form and accumulate under the retina between the retinal pigmented epithelium (RPE) layer and the Bruch's membrane, which supports the retina. Drusen are often found in the eyes of older people, but an increase in the size and number of these deposits is frequently the first sign of macular degeneration. Over time, drusen are associated with deterioration of the macula and the death of RPE and photoreceptor cells, resulting in a blurring or spotty loss of clear, straight-ahead vision.

Wet macular degeneration occurs when abnormal blood vessels grow behind the macula as RPE and photoreceptor cells die. The Bruch’s membrane begins to break down, usually near drusen deposits, and new blood vessels grow. This growth is called neovascularization. These vessels are very fragile and can leak fluid and blood, resulting in scarring of the macula and the potential for rapid, severe damage. Straight-ahead vision can become distorted or lost entirely in a short period of time, sometimes within days or weeks. Wet macular degeneration accounts for approximately 10 percent of the cases, but it results in 90 percent of the cases of legal blindness. All wet AMD is considered advanced.

Yes, there are several forms of juvenile macular degeneration (JMD), and all are inherited. The most common form of JMD is Stargardt's disease, also called fundus flavimaculatus or macular dystrophy, which normally develops in the childhood or teen years. Best disease or vitelliform macular degeneration is the second most common form of JMD; symptoms usually occur between birth and age 7. People in their thirties or forties can develop genetic forms of macular disease such as Sorsby's fundus dystrophy, Behr's dystrophy and Doyne's honeycomb retinal dystrophy. Finally, myopic macular degeneration can occur in people who are severely near-sighted due to extreme elongation of the eyeball. This condition can result in macula tears and bleeding beneath the retina.

Age-related macular degeneration (AMD) typically affects individuals over 50 years old. Scientific evidence shows that genes may play a role in the development of nearly three out of four cases of this devastating eye disease.

Several genes are believed to be strongly associated with the risk of developing AMD:

• Factor H and Factor B genes are responsible for proteins that help regulate inflammation in the part of the immune system that attacks diseased and damaged cells. According to study results published in 2006 by Columbia University, 74 percent of AMD patients carry certain variants in one or both of these genes, and these may significantly increase their risk of developing it.
  
  
• PLEKHA1 – a gene located on chromosome 10; researchers believe it may increase the risk of developing AMD. Like Factors H and B, PLEKHA1 appears to be involved in the cellular processes related to inflammation.
  
  
• LOC387715 – A certain variation of this gene appears to increase the risk of developing AMD. This risk is further heightened if a person with this gene variation also smokes.
  
  
• HTRA1 – Scientists have identified a link between a mutation in this gene and the development of AMD. Specifically, the HTRA1 mutation is thought to be associated with the formation of drusen (yellow deposits of waste products under the retina that are often a sign of dry AMD), and may also promote the growth of fragile new blood vessels typical of wet AMD.
  
  
• Complement C3 – Researchers have found that a variant in this gene increases the risk of developing the wet and dry forms of AMD. This gene plays an important role in the immune system, leading scientists to believe that inflammation is a vital part of the AMD disease process.

Other gene candidates are being studied to determine their role in AMD. While there is definitely a strong genetic component to this disease, it is highly likely that its development is due to a combination of multiple factors including gene mutations or variations and environmental factors such as sunlight exposure, diet and smoking.

It is possible to develop AMD in only one eye. However, as the disease progresses, both eyes may become affected. If advanced AMD occurs in one eye, there is a much greater risk of developing advanced AMD in the other.