MACULAR DEGENERATION

Dr. Steven H. Sherman, M.D. Ophthalmologist Annapolis
Dr. Steven H. Sherman, M.D.

Adult macular degeneration is traditionally described as that form of the disease that affects individuals over the age of 55 years. However, we have recently discovered that a significant number of these individuals may have a major genetic component that contributes to the disease.

What does macular degeneration do to your vision?

Your retina contains an extraordinary photosensitive array of cells that line the back of your eye. The light falling onto these cells in the retina is transformed into electrical signals which are transmitted to the brain centers that process and interpret them. The most concentrated collection of photosensitive cells in your retina, including those that enable critical color and fine detail vision, are found in the Bulls-Eye center zone in an area called the macula. Macular degeneration is the imprecise historical name given to that group of diseases that causes sight-sensing cells in the macular zone of the retina to malfunction or lose function and results in debilitating loss of vital central or detail vision.

Macular Degeneration Annapolis

Because the brain cleverly learns to compensate and fill in the missing part of the picture in early cases with spotty macular cell damage or dysfunction, most people only present to their ophthalmologist when disease is fairly advanced. Compared to the huge numbers of people affected (over 12 million), research efforts toward discovery of cause and cure by government, public and private institutions are inappropriately small.

What are the Symptoms of Macular Degeneration?

Macular degeneration can cause different symptoms in different people. Sometimes only one eye loses vision while the other eye continues to see well for many years. The condition may be hardly noticeable in its early stages. But when both eyes are affected, reading and close up work can become difficult. See: Pictorials

If you have been diagnosed with adult macular degeneration you are in good company. Another case of adult macular degeneration is diagnosed every three minutes in the United States of America. One in six Americans between the ages of 55 and 64 will be affected while one in four Americans between 64 and 74 will be smitten. One in three over the age of 75 will be affected. Each year 1.2 million of the estimated 12 million people with macular degeneration will suffer severe central vision loss. Each year 200,000 individuals will lose all central vision in one or both eyes.While the causes of macular degeneration are unknown, some tantalizing clues have become available. Genetic researchers, supported in part by the Macular Degeneration Foundation, have recently discovered a group of genes termed ABCR.

Possession of these genes may increase the likelihood of an individual developing macular degeneration by approximately 30 percent. However, most macular diseases have a complex genetic makeup compared with single gene-causation diseases. In most individuals macular degeneration is likely due to both environmental and genetic factors that combine to cause damage and disease.

Genetic typing of patients with macular degeneration is likely to assume more and more importance in the future. It will enable ophthalmologists to identify high-risk individuals and to better understand the relationships between genetic defects, the appearance of the macula and how the disease progresses. This information will hopefully provide scientists with some of the tools they need to develop therapies that can prevent, slow and even arrest the progression of macular degeneration.

What can you or your loved one do if diagnosed with macular degeneration?

First it is important to modify those environmental risk factors that we know about.

  • 1. Eat a low-fat, low cholesterol diet.
  • 2. If you are post menopausal, you should consult with your physician concerning estrogen replacement therapy. This may have a favorable impact upon cholesterol lipid levels that play a role in worsening the disease.
  • 3. Wear sunglasses with UV protection.
  • 4. Try to consume at least two servings of leafy dark green vegetables per day.
  • 5. Do not smoke and avoid exposure to secondhand smoke.
  • 6. Eat food and or supplements rich in vitamin E,C and Lutein. Lutein is a plant antioxidant found in high quantities in spinach, kale and other dark green, leafy vegetables.

Some emerging theories about what may play a role in causing or worsening macular degeneration:

  • 1. The macular contains many highly active and sensitive photoreceptors that require and consume a great deal of energy. Generating this energy requires a constant, rich supply of oxygen, nutrients and ions. Consequently, the macula has one of the highest rate of blood flow through its supply vessels. Anything that interferes with this necessary rich blood supply can cause the macula to malfunction and possibly become diseased.
  • 2. Smoking can reduce this vital blood supply by contributing to narrowing of the blood vessels and thickening of the blood, as it does in the heart and brain where this process contributes to heart attacks and strokes.
  • 3. A high-fat, high cholesterol diet can lead to fatty plaque deposition in the macular vessels hampering blood flow.
  • 4. A shortage of antioxidants may also increase the tendency for fatty deposits to stick to blood vessel walls.

Source:Macular Degeneration Foundation, www.eyesight.org

There are 2 types of Macular Degeration:

Dry AMD is most common type of macular degeneration and affects 90% of the people who have the condition. In the dry form, there is a breakdown or thinning of the layer of retinal pigment epithelial cells (RPE) in the macula. These RPE cells support the light sensitive photoreceptor cells that are so critical to vision. When we look at something, the photoreceptors (rods and cones) gather the images and send them to the brain, where vision takes place.

The death or degeneration of these cells is called atrophy. Hence, dry AMD is often referred to as atrophic AMD. It is characterized by the presence of drusen (dots of yellow crystalline deposits that develop within the macula) and thinning of the macula. Dry or atrophic MD reduces one's central vision and can effect color perception. Generally, the damage caused by the "dry" form is not as severe or rapid as that of the "wet" form. However, over time, it can cause profound vision loss. There are no medical treatments for dry macular degeneration but there is one procedure that may help to improve your central vision. Because of the lack of treatments, it is important for you to control your risk factors. We know that certain lifestyle factors can contribute to the development and progress of AMD, while others may slow down the process.

Wet macular degeneration is the more severe type of AMD. Although it affects only 10 percent of those who have the condition, it accounts for 90 percent of the severe vision loss caused by macular degeneration. With this type, the membrane underlying the retina thickens, then breaks. The oxygen supply to the macula is disrupted and the body responds by growing new, abnormal blood vessels. These begin to grow through the breaks of the membrane behind the retina towards the macula, often raising the retina.

To visualize this, imagine the roots of a tree growing and spreading until they actually uproot a sidewalk. Then imagine rainwater seeping up throughout the cracks. These abnormal blood vessels (the "roots) tend to be very fragile. They often grow, leak or bleed, causing scarring of the macula. This fluid is called exudate and wet AMD is sometimes called exudative macular degeneration. This damage to the macula results in rapid central vision loss. Once this vision is destroyed, it cannot be restored. There are several treatment options for wet AMD which can be very effective if applied early. Fortunately for people with wet macular degeneration, there are several treatment options and more are being developed. These are aimed at sealing off the leaking blood vessels (with a laser and light sensitive drug) and/or preventing the blood vessels from growing back (these last are called anti-angiogenic therapies).

Repeated treatments are necessary, as often as once a month, but doctors are now finding that treatments can be spaced further apart and still be effective. Each eye is different, so your doctor will watch carefully how you respond and will recommend what works best for you. With multiple treatment options available, your doctor can advise you which therapy will probably be best for your case. After reviewing the photographs taken after treatment, your doctor will decide whether continuing that treatment is the best choice. Sometimes, the retinal specialist will start you on one treatment for a few months and then switch you to another therapy. Or, you may start with one therapy and another will be added to it.

Early detection and treatment are key to good results of any therapy for wet macular degeneration. All these treatments work better if applied early in an episode of bleeding. The goal of current treatments is to stop or slow the progression of wet AMD. While it is possible to restore some vision in patients treated early, none of the therapies can restore vision in an eye with scarring.

If you have questions about your treatment options for macular degeneration, visit Ophthalmology Associates of Greater Annapolis and schedule an appointment with one of our board certified opthalmologists.

Source: Macular Degeneration Partnership, www.amd.org

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