Age-Related Macular Degeneration (AMD)
Eye Conditions & Care | Eye Conditions | Age-Related Macular Degeneration (AMD)
Age-Related Macular Degeneration (AMD) causes progressive loss of central vision due to the degeneration or breaking down of the macula. The macula is the central portion of the retina at the back of the eye. The risk of developing macular degeneration increases with age. The disease most often affects people in their sixties and seventies. Macular degeneration is the most common cause of vision loss in people over the age of fifty-five.
Symptoms of AMD
People with macular degeneration may first notice a blurring of central vision especially when performing visually detailed tasks such as reading and sewing. Also, straight lines might appear wavy (such as doorframes and steps). In its earliest stages, AMD can be difficult to diagnose. The extent of central vision loss varies according to the type of macular degeneration. Sometimes it progresses so slowly that people do not notice a change in their vision and in others the deterioration is very rapid and can appear to happen overnight. As the disease progresses, blind spots form within central vision. In most cases, if one eye has macular degeneration, the other eye will also develop the disease.
There are two types of age related (or late onset) macular degeneration known as wet and dry. It is possible to experience both forms at the same time, in one or both eyes. It is not uncommon for a patient with the dry form to develop the wet form later.
Dry form
Dry AMD is the more common form. It is also referred to as atrophic, nonexcudative, or drusenoid form. This form accounts for 90 percent of Age-Related Macular Degeneration.
Dry AMD is characterised by the build-up of drusen, small yellowish deposits, beneath the macula. The layer of photo receptor cells in the macula begin to atrophy, or die, as some of the cells break down. Often if one eye has dry AMD, the other eye will also show some signs of the condition.
There is currently no cure or treatment for dry form AMD. Some research suggests that vitamin supplements may help slow down the progression of "dry" AMD. They do not restore sight, but it is possible that they play a part in prolonging vision.
Wet form
Wet AMD accounts for 10 percent of patients with late onset macular degneration. It is also called choroidal neovascularisation, subretinal neovascularisation, exudative form, or disciform degeneration.
In wet AMD, new abnormal blood vessels begin to grow beneath the macula, in a thin layer of tissue called the choroid. The choroid is the main source of oxygen and nutrients for the retinal photo receptors, and it is the only blood supply for the macula. New fragile blood vessels develop which may leak fluid and blood, and then cause the choroid and retina to deteriorate. This causes the retinal layer to blister under the macula, and the photo receptor cells to degenerate. At this stage, there is marked disturbance of vision in the affected eye.
Laser photocoagulation can help some people with wet AMD. In this treatment, laser light rays are directed into the eye and focused on a small spot on the macula. The laser destroys the blood vessels growing beneath the retina and seals leaky areas. This treatment cannot restore vision already lost from AMD, so it is critical that it be applied as early as possible, before vision impairment has progressed. A badly damaged macula will not benefit from laser treatment.
There are a number of different treatments, called Anti VEGF therapies, being tested. They involve an injection into the eye that stops the development of the new leaky blood vessels. Lucentis (ranibizumab) and Macugen (pegaptanib) are 2 types of drugs that have been used successfully. This has to be repeated about every six weeks. Like Laser photocoagulation, this type of treatment is limited to people whose wet AMD affects the middle of the macula and its main aim is to stop the condition from getting worse. However, in some cases it has been shown to restore some of the vision already lost and it can help with a wider range of people than PDT.
What causes AMD?
The exact cause for AMD is not known, however there are a number of risk factors which have been identified. There appears to be a genetic factor whether someone develops AMD or not which is still being researched. Women appear more likely to develop the condition. Smoking has been linked to the development of macular degeneration in research. Protecting the retina by the use of sunglasses and eating a healthy diet can also help protect against sight loss through macular degeneration.
Other sources of information about AMD:
www.amd.org
www.amdalliance.org