Macular degeneration is damage or breakdown of the macula. The macula is a small area at the back of the eye that allows us to see fine details clearly. When the macula doesn't function correctly, we experience blurriness or darkness in the center of our vision. Macular degeneration affects both distance and close vision, and can make some activities - like threading a needle or reading - difficult or impossible.
Although macular degeneration reduces vision in the central part of the retina, it does not affedct the eye's side, or peripheral vision. For example, you could see the outline of a clock but not be able to tell what time it is.
Macular degeneration alone does not result in total blindness. People continue to have some useful vision and are able to take care of themselves.
What causes macular degeneration?
Many older people develop macular degeneration as part of the body's natural aging process.
The two most common types of age-related macular degeneration are "dry" (atrophic) and "wet" (exudative):
"Dry" macular degeneration (atrophic)
Most people have "dry" macular degeneration. It is caused by aging and thinning of the tissues of the macula. Vision loss is usually gradual.
"Wet" macular degeneration (exudative)
"Wet" macular degeneration accounts for about 10% of all cases. It results when abnormal blood vessels form at the back of the eye. These new blood vessels leak fluid or blood and blur central vision. Vision loss may be rapid and severe.
But when both eyes are affected, the loss of central vision may be noticed more quickly.
Following are some common ways vision loss is detected:
- Words on a page look blurred
- A dark or empty area appears in the center of vision
- Straight lines look distorted
How is macular degeneration diagnosed?
Sometimes special photographs, called fluorescein angiograms (FA), are taken to find abnormal blood vessels under the retina. Fluorescent dye is injected into your arm and your eye is photographed as the dye passes through the blood vessels in the eye. Also an Optical Coherence Tomography (OCT) could be performed in addition to the FA.
How is macular degeneration treated?
Macular degeneration cannot be reversed. Its impact, however, can be reduced.
Certain types of wet macular degeneration can be treated with laser surgery, a brief outpatient procedure that uses a focused beam of light to slow or stop leaking blood vessels that damage the macula. A treatment called photodynamic therapy (PDT) uses a combination of a special drug and laser treatment to slow or stoop leaking blood vessels. Another form of treatment targets a specific chemical in your body that is critical in causing abnormal blood vessels to grow under the retina. That chemical is call vascular endothelial growth factor (VEGF). Anti-VEGF drugs block the trouble-causing VEGF, reducing the growth of abnormal blood vessels and slowing their leakage.
Photodynamic Therapy with Visudyne (PDT)
In early stages of wet aged-related macular degeneration (ARMD), Photodynamic therapy with Visudyne (PDT) is used. This method of treatment employs a low-intensity laser light to activate a dye (verteporfin or Visudyne) that is injected into the vein intraveniously. The activated dye damages and destroys the abnormal blood vessels under the retina that cause visual loss in wet ARMD. It avoids the scarring caused by conventional hot laser treatments.
Avastin or Bevacizumab Intravitreal InjectionAvastin or Bevacizumab injections are another treatment of wet ARMD. Avastin was not initially developed to treat eye conditions, therefore, it is not FDA approved. Avastin is considered to be an “off-label” treatment of wet ARMD. Avastin is injected into the eye in the clinic using local anesthesia. Avastin works by blocking a substance known as vascular endothelial growth factor or VEGF. Blocking or inhibiting VEGF helps prevent further growth of the blood vessels. Since Avastin is not FDA approved, some insurance companies do not cover the cost for the drug or the injection of the drug. Avastin is normally injected into the eye every six to eight weeks. Lucentis or Ranibizumab injections are another treatment of ARMD. Lucentis was approved for clinical use by the FDA in June 2006 for treatment of ARMD. Lucentis is very similar to Avastin; therefore, it also blocks vascular endothelial growth factor or VEGF. Blocking or inhibiting VEGF helps prevent further growth of the blood vessels. Lucentis is only approved for treatment of ARMD.
Thermal Laser Photocoagulation Surgery
Thermal laser photocoagulation surgery is used to treat ARMD. But this surgery is an option for less than one-fourth of the people with wet ARMD. Whether your ARMD can be treated by laser photocoagulation surgery or other surgery depends on the location and development of abnormal blood vessels under the retina.
None of the treatments previously listed are a cure for wet ARMD, but they can slow down the progression of the disease or prevent further loss of central vision. In clinical studies, most patients found that their vision remained the same. Only a few patients found their vision actually improved with treatment. However, without treatment, vision loss from wet ARMD may progress until a patient has no central vision left.
Your ophthalmologist can prescribe optical devices or refer you to a low-vision specialist or center. A wide range of support services and rehabilitation programs are also available to help people with macular degeneration maintain a satisfying lifestyle.
Because side vision is usually not affected, a person's remaining sight can be very useful. Often, people can continue with many of their favorite activities by using low-vision optical devices such as magnifying devices, closed-circuit television, large-print reading materials,, and talking or computerized devices.
Testing your vision with the Amsler grid
You can check your vision daily by using an Amsler grid like the one pictured here. You may find changes in your vision that you wouldn't notice otherwise. Putting the grid on the front of your refrigerator is a good way to remember to look at it each day. (Click on the hyperlink above to view the grid. Print the grid to perform the test).
To use the grid:
- Wear your reading glasses and hold this grid at 12-15 inches in good light
- Cover one eye
- Look directly at the center dot with the uncovered eye
- While looking directly at the center dot, note whether all lines of the grid are straight or if any areas are distorted, blurred or dark
- Repeat this procedure with the other eye
- If any area of the grid looks wavy, blurred, or dark, contact your ophthalmologist immediately
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