Age Related Macular Degeneration
Age related macular degeneration (ARMD or AMD) is a disease that blurs the sharp, central vision you need for "straight-ahead" activities such as reading, sewing, and driving.
Age related macular degeneration affects the macula which is the part of the eye that allows you to see fine detail. It causes irreversible loss of central vision over a period of time and is the leading cause of permanent visual loss in people over the age of 65 years in the Western world.
Who are prone to age related macular degeneration?
The exact cause of age related macular degeneration is unknown and may be caused by a variety of factors. In general, the disease occurs only in older people. It is also more common among Caucasians, people with a family history of the disease, smokers, females, and people with low dietary intake of antioxidants.
Types of age related macular degeneration
There are two types of age related macular degeneration:
- nonexudative ("dry" or atrophic) and
- exudative ("wet")
Both forms of age related macular degeneration are progressive and usually affect both eyes. They differ however, in their appearance, prognosis and management.
Dry AMD is more common (85% to 90% of cases) than wet AMD. However, vision loss is more gradual and less severe compared to wet AMD. Dry AMD may result from the aging and thinning of macular tissues, depositing of pigment in the macula or a combination of the two.
Dry AMD can worsen and cause vision loss without turning into wet AMD. Alternatively, the dry form may also suddenly turn into wet AMD. There is no way of telling if, or when dry AMD will turn into the wet form. In wet AMD, new blood vessels grow beneath the retina and leak blood and fluid. This leakage causes retinal cells to die and creates blind spots in central vision. In wet AMD, loss of central vision can occur quickly and is more severe than dry AMD. Although it afflicts only about 10% of those with AMD, it accounts for 90 percent of the blindness caused.
Symptoms of Age Related Macular Degeneration
Some of the signs and symptoms of age related macular degeneration include loss of central vision, distorted vision, or difficulty reading or performing tasks that require the ability to see detail. Do approach an ophthalmologist to have your eyes checked if you develop any of these signs and symptoms.
Treatment of Age Related Macular Degeneration
There is no proven medical therapy for dry AMD. Dietary supplements such as vitamins C, E, beta-carotene, and zinc have been shown to decrease the risk of vision loss in patients with intermediate to advanced dry AMD. The Age Related Eye Disease Study (AREDS) showed that people with the intermediate stage of dry AMD could reduce their risk of progressing to advanced dry AMD by about 25% by taking a special high-dose formula of the supplements. It is important to note that high-dose vitamins, may present a risk for some people. Smokers taking high doses of beta-carotene may increase their risk of lung cancer. Do check with your pharmacist or doctor before you decide to take any supplements.
In selected cases of wet AMD, laser photocoagulation is effective for sealing leaking or bleeding vessels. Unfortunately, laser photocoagulation usually does not restore lost vision, but it may prevent further loss. Another treatment option is photodynamic therapy, which is effective in stopping abnormal blood vessel growth in some patients with wet AMD. This new type of laser treatment is far less damaging than laser photocoagulation and is the treatment of choice in many cases. Other promising treatments include anti-VEGF therapy (works by blocking a key signal that causes abnormal vessels under the macula to grow and leak) and steroid therapy. It should be noted that none of these treatments can restore vision that has already been lost.
Early diagnosis is critical for successful treatment of wet AMD. Patients can help the doctor detect early changes by monitoring vision at home with an Amsler grid. This resembles a checkerboard and consists of a 10 cm square divided into smaller 5 mm squares. The grid is placed at a comfortable reading distance and one eye is tested each time. Cover one eye and stare at a black dot in the center of the grid. While staring at the dot, if you notice that the straight lines in the pattern appear wavy or that some of the lines are missing, these are signs of wet AMD and you should consult an ophthalmologist immediately.
Related Link: Article on Age Related Macular Degeneration - How it affects you?