What Is It?
Age-related macular degeneration (AMD) damages the eyesight of 13 million Americans. In many cases, the onset of AMD drastically limits one’s mobility and devastates one’s sense of independence and security. It strikes painlessly, disrupting the central vision needed to read and to write, to drive and to watch TV, to thread a needle, to see a loved one’s face.
AMD most often affects persons in their late fifties or sixties just when they are preparing to enjoy their leisure years. It is ironic that medical progress in combating fatal diseases has extended the life span of millions who then fall prey to AMD and other age-related diseases. An estimated 400,000 Americans develop a severe form of AMD each year, making it the leading cause of functional blindness in people 65 or older. One-third of the population over age 75 is likely to develop AMD.
At the present time, there is no known cure or lasting treatment for AMD and, until recently, it had been considered impossible to treat in any form. However, new advances in eye research offer hope to those whose lives have been affected by this disease or in whom the disease is likely to develop.
Technically, AMD is a group of similar diseases that destabilize the macula, a tiny section of the retina in the back of the eye. The retina is a paper thin tissue that receives images and converts them into electrical signals sent to the brain through the optic nerve. The retina contains two forms of light-receiving cells called rods and cones. The macula, which is about the size of a pinhead, is rich in cone cells which give us our color and central vision. Rod cells help us to see at night. There are two main types of macular degeneration–the “dry” type and the “wet” type. In either case, the disease leaves peripheral vision intact and most of those afflicted retain some usable sight.
Patients with wet macular degeneration develop new blood vessels under the retina. This causes hemorrhage, swelling and scar tissue but it can be treated with laser in some cases. Dry macular degeneration although more common, typically results in a less severe, more gradual loss of vision.
Dry macular degeneration although more common, typically results in a less severe, more gradual loss of vision.
The “dry” (atrophic) form accounts for 9 out of 10 AMD cases. It is usually slow to develop and does not cause total loss of central vision. Dry AMD is characterized by a thinning or deterioration of tissue underneath the macula and a slow breakdown of the cone cells.
The “wet” (or oxidative) form occurs in only 10% of AMD patients, but it causes 90 percent of the cases of severe visual loss due to the disease. In “wet” AMD, abnormal blood vessels develop rapidly under the retina and leak blood or fluid that damage the macula causing severe and sometimes sudden vision loss. The wet form often results in the growth of dense scar tissue.
The exact cause of AMD is unknown but it is almost always age-related and the incidence is higher in women than in men. Although AMD is not an inherited disease in the classic sense, it may be clustered in some families. The condition is more prevalent among Caucasians than among African-Americans, and it appears to be most common in people with blue or light-colored eyes. Additional risk factors linked to the condition may include, among others, hypertension, smoking and excessive exposure to ultraviolet (UV) rays, especially from the sun.
Anyone over 50, especially those with a family history of AMD, should have their eyes examined regularly by their ophthalmologist and should use the Amsler grid at home. AMD is usually painless. The “dry” type can be very slow in forming, but the “wet” type is likely to develop quickly and may cause sudden visual loss. In some cases, the disease develops in one eye but does not affect the other for many years. AMD symptoms vary and may include:
- gradual burning and/or the development of blind spots in the center of the field of vision. difficulty in picking out details, near and far
- straight lines appear to be wavy and shapes are distorted
- printed words appear to be blurred
- dimmed color vision
Recent advancements in eye research offer new hope to victims of AMD. In a small percentage of people with wet AMD, laser therapy can be used to destroy abnormal blood vessels and to seal leaks, thereby retarding the disease.
The treatment is usually a painless outpatient procedure. But even if the treatment succeeds in slowing the rate of vision loss, the laser may leave a permanent blind spot where it has been applied. In effect, the individual may lose some sight in order to slow the disease and extend the use of the remaining central vision. Nonetheless, recurrence of new vessels and leakage are common even after laser therapy.
No proven treatment exists for the dry form of AMD. However, researchers have discovered that a healthy macula has two yellowish pigments–the antioxidants known as lutein and zeaxanthin–that may block harmful blue light from damaging the retina. Studies suggest that nutritional supplements containing these antioxidants may slow degeneration, and further investigation of these preliminary results is underway.
Can AMD Be Prevented?
No one knows how to prevent AMD but the following practices may help to delay the onset of the disease:
- maintain a proper diet including fruits and vegetables rich in antioxidants, especially leafy, green vegetables such as spinach and collard greens
- wear sunglasses and brimmed hats to avoid excessive sunlight
- don’t smoke, since smoking reduces protective antioxidants in the eye.
- Your ophthalmologist can also recommend other lifestyle changes that may help preserve your vision.
Coping With Vision Loss
Until scientists find a cure or lasting treatment for AMD, patients should consult with an ophthalmologist and a low vision specialist for advice on making use of a wide variety of products and rehabilitation techniques to maximize remaining vision and to receive individual training to maintain mobility and independence in daily living. It is also important for a patient to:
- understand that the condition impacts the day-to-day lives of the whole family. remember that there are many resources and rehabilitation services available to help cope with AMD.
- be aware that many useful low vision devices exist such as large print computer and TV screens; talking clocks, scales and books; and check writing devices. get a statement from the doctor concerning the diagnosis for legal and tax purposes.
Hope For The Future
Research to Prevent Blindness (RPB) spearheads the national research effort to find a lasting cure or preventative for AMD. RPB facilitates these efforts through its general research program and through funding designated specifically for AMD research and treatment. Laser therapy-the first treatment known to be effective in treating some cases of the wet form of AMD-relies on a technology developed with an RPB grant. Many promising avenues of scientific investigation into AMD are currently receiving RPB support. They include research into:
- more advanced laser radiation therapies
- photodynamic therapy (the use of low intensity lasers to activate chemicals that stop blood vessel growth)
- retinal cell transplantation
- macular translocation (moving the macula away from the underlying diseased tissue)
- surgical removal of abnormal blood vessels and of hemorrhages
- gene therapy
- development of drugs to inhibit blood vessel growth
- improved means of administering pharmacological agents
After a detailed retinal examination by your ophthalmologist, you might wish to ask if any of these experimental approaches holds particular promise in your case.