About the macula
The eye is shaped like a ball. The pupil, close to the front, is the opening, which allows light to enter the eye. Just behind the pupil is the lens, which focuses the light on the retina at the back of the eye. The retina is a delicate tissue, which converts the light into images, and sends them to the brain. The macula is a small area at the very centre of the retina.
The macula is very important and is responsible for what we see straight in front of us, allowing us to see fine detail for activities such as reading and writing, as well as our ability to see colour.
About macular degenerationSometimes the delicate cells of the macula become damaged and stop working, and there are many different conditions which can cause this. If it occurs later in life, it is called "age-related macular degeneration", also often known as AMD.
Broadly speaking, there are two types of macular degeneration or AMD, usually referred to as "wet" and "dry". This is not a description of what the eye feels like but what the ophthalmologist (eye specialist) can see when looking at the macula.
Age-related macular degeneration is the most common cause of vision loss in the United States for people 50 or older, and the chance of getting the disease increases with age. It is a primary bilateral disease of the Retinal Pigment Epithelium (RPE) with secondary degenerative effects upon the overlying retina and underlying choroidal vessels. As a result, central vision may deteriorate.
Causes of Macular Degeneration
The following factors can contribute to macular degeneration : -
- Sunlight exposure
Genetics - There appear to be a number of genes which can be passed through families which may have an impact on whether someone develops AMD or not.
Age - AMD is an age related condition so growing older makes the condition more likely.
Nutrition - Research suggests some vitamins and minerals can help protect against AMD.
Smoking - Smoking has been linked by a number of studies to the development of AMD. It has also been shown that stopping smoking can reduce the risk of AMD developing.
Sunlight - Some research suggests that lifetime exposure to sunlight may affect the retina. It is a good idea to wear sunglasses to protect the eyes.
Gender - Women seem more likely to develop macular degeneration than men.
Although nothing can be done about age, gender and the genes we inherit, it is possible to control the other more environmental factors that seem to be linked to AMD. Protecting your eyes from the sun, eating a well balanced diet with plenty of fresh fruits and vegetables and stopping smoking may all help to delay the progress of AMD.
Dry Macular Degeneration
This type of macular degeneration is the most common, and typically results in a gradual loss of vision (usually over years to decades). One of the characteristics of this disease is the presence of drusen, small, yellowish deposits that form within the layers of the retina. Another sign is loss of pigment in the retina. With treatment, the chances that the dry form of macular degeneration may progress to the wet form are significantly reduced.
Wet Macular DegenerationAbout 10 percent of patients who suffer from macular degeneration have wet AMD. Wet AMD is a serious condition that can lead to substantial vision loss even with aggressive treatment. However, treatment has been shown to increase the chances of regaining some vision, maintaining the patient's current residual vision, and/or decreasing the chances of losing further vision. It occurs when new vessels form to improve the blood supply to oxygen-deprived retinal tissue. Because the new vessels are very delicate, they break easily and cause bleeding and damage to surrounding tissue.
Signs and SymptomsAge-related macular degeneration usually produces a slow, painless loss of vision. In rare cases, however, vision loss can be sudden. Early signs of vision loss from AMD include shadowy areas in your central vision or unusually fuzzy or distorted vision.
Viewing a chart of black lines arranged in a graph pattern (Amsler grid) is one way to tell if you are having these vision problems. See how an Amsler grid works by taking a macular degeneration test.
Eye care practitioners often detect early signs of macular degeneration before symptoms occur. Usually this is accomplished through a retinal exam. When macular degeneration is suspected, a brief test using an Amsler grid that measures your central vision may be performed.
If your eye doctor detects some defect in your central vision, such as distortion or blurriness, he or she may order a fluorescein angiography to examine the retinal blood vessels surrounding the macula.
- Loss of central vision This is usually gradual for patients with dry macular degeneration. Patients with the wet type may experience a sudden decrease of central vision
- Straight lines may appear wavy or bent
Difficulty reading or seeing details
Who Gets Age-Related Macular Degeneration?Commonly named risk factors for developing macular degeneration include : -
- Obesity and Inactivity. Overweight patients with macular degeneration had more than double the risk of developing advanced forms of macular degeneration compared with people of normal body weight, according to one study reported in Archives of Ophthalmology . In the same study, those who performed vigorous activity at least three times weekly reduced their risk of developing advanced AMD, compared with inactive patients.
- Heredity. As stated above, recent studies have found that specific variants of different genes are present in most people who have macular degeneration. Studies of fraternal and identical twins may also demonstrate that heredity is a factor in who develops AMD and how severe it becomes.
- High Blood Pressure (Hypertension). Investigative Ophthalmology and Vision Science reported a study in Rotterdam, The Netherlands demonstrating that high blood pressure may be associated with development of macular degeneration.
- Smoking. Smoking is a major risk factor found in one British study to be directly associated with about 25 percent of AMD cases causing severe vision loss. The British Journal of Ophthalmology in early 2006 also reported study findings showing that people living with a smoker double their risk of developing AMD.
- Lighter Eye Color. Because macular degeneration long has been thought to occur more often in lighter skinned populations, particularly in people with light eye color, some researchers theorized that the extra pigment found in darker eyes was a protective factor against development of the eye disease during sun exposure. But no conclusive evidence as yet has linked excessive sun exposure to development of AMD.
A small study reported in the British Journal of Ophthalmology (January 2006) found no connection between the eye disease and sun exposure. In fact, the same study found no relation at all between lighter eye color, hair color and AMD. That finding is contradicted by several earlier studies indicating that lighter skin and eyes are associated with a greater prevalence of AMD.
- Drug Side Effects. Some cases of macular degeneration can be induced from side effects of toxic drugs such as Aralen (chloroquine, an anti-malarial drug) or phenothiazine. Phenothiazine is a class of anti-psychotic drugs, including brand names of Thorazine (chlorpromazine, which is also used to treat nausea, vomiting and persistent hiccups), Mellaril (thioridazine), Prolixin (fluphenazine), Trilafon (perphenazine) and Stelazine (trifluoperazine).
The American Academy of Ophthalmology notes that findings regarding AMD and risk factors have been contradictory, depending on the study. The only risk factors consistently found in studies to be associated with the eye disease are aging and smoking.
Dry vs. Wet Macular DegenerationMacular degeneration is classified as either wet (neovascular) or dry (non-neovascular).
How Macular Degeneration Is TreatedThere is as yet no outright cure for age-related macular degeneration, but some treatments may delay its progression or even improve vision.
Treatments for macular degeneration depend on whether the disease is in its early-stage, dry form or in the more advanced, wet form that can lead to serious vision loss. No FDA-approved treatments exist yet for dry macular degeneration, although nutritional intervention may help prevent its progression to the wet form.
For wet AMD, treatments aimed at stopping abnormal blood vessel growth include FDA-approved drugs of Lucentis, Macugen and Visudyne used with Photodynamic Therapy or PDT. Lucentis has been shown to improve vision in a significant number of people with macular degeneration. [For more details, read our article about macular degeneration treatments.
Laser PhotocoagulationIn some cases of wet macular degeneration, laser photocoagulation is used to seal leaking or bleeding vessels, which are located outside of the center of the macula (fovea). Laser photocoagulation usually does not restore lost vision, but it may prevent further loss for some patients.
Photodynamic Therapy (Visudyne® Drug Treatment)Photodynamic therapy is a newer type of laser treatment that is sometimes preferred over photocoagulation when the target pathology is involving the center of the macula (fovea) and is not involving the optic nerve, and is not larger than the laser's maximum beam size. It involves using the light activated drug Visudyne® combined with a laser to stop abnormal blood vessel growth in some patients with wet AMD. However, it only works for patients with a well-defined, distinctive pattern of new blood vessel growth under the retina.
If you undergo photodynamic therapy, Visudyne® will be injected into your arm. As the drug passes though the retinal blood cells, your doctor will shine a non-thermal laser into your eye to activate it. This produces a chemical reaction that destroys abnormal blood vessels.
Vitamin SupplementsRecent studies have revealed that people with a diet high in fruits and vegetables (especially leafy, dark green vegetables) are less likely to suffer from macular degeneration. Studies have also shown that taking supplements such as vitamins C and E, beta-carotene (not to be used by actively smoking patients), and zinc may lower the chances that macular degeneration will get worse in some patients. Therefore, we suggest that patients with this condition consider taking antioxidant and zinc supplements. However, more research needs to be done on this subject and supplements are not recommended for all patients. Please speak to your doctor for more information.
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