What is Age-related Macular Degeneration?
Figure 1: Normal Macula
Age-related macular degeneration (AMD) is the leading cause of blindness in people over 65 years of age. There is deterioration of the central part of the retina, the macula (figure 1), which is the area that allows us to see color and detail. This is essential for activities such as driving, reading, and threading a needle. When the macula is not functioning properly, we experience blurriness and distortion in the center of our vision.
Both distance and near vision are affected. Total blindness does not occur. Therefore, people continue to have some useful vision and are generally able to take care of themselves.
The peripheral retina surrounds the macula. It is responsible for side and night vision, and it is not affected in AMD. For example, you might see the outline of a clock, but would not be able to tell what time it is.
Macular Degeneration Causes and Types
AMD is most commonly a result of the body’s natural aging process. There are two types of AMD. One is the dry or atrophic type (figures 2 and 3) and the other is the wet or exudative type (figures 4 and 5).
Dry AMD
Most people have the dry type of macular degeneration. In this type, the tissues break down and become thin with aging causing gradual loss of vision. Yellowish deposits called drusen accumulate under the retina (figure 2) and they usually do not affect vision significantly. In the more advanced stage, there can be a large atrophic area, referred to as geographic atrophy (figure 3), which is associated with loss of central vision.
Figure 2: Dry Macular Degeneration with Drusen
Figure 3: Dry Macular Degeneration with Geographic Atrophy
Wet AMD
Wet macular degeneration accounts for about 10% of all cases. It results when aging of the retina is compounded by growth of abnormal blood vessels, called choroidal neovascularization, underneath the macula. These vessels leak fluid and/or blood which distort the retinal tissue (figures 4 and 5) and blur central vision. Visual loss may be rapid and severe with significant distortion as a result of swelling of the retinal tissue and dense scar tissue formation (figure 5).
Figure 4: Wet Macular Degeneration with Blood Under the Macula.
Figure 5: Wet Macular Degeneration with scar tissue formation.
Do I Have An Increased Risk For Macular Degeneration?
The most important risk is increasing age. Other risks include family history, European descent, smoking, obesity, excessive exposure to sunlight, high blood pressure and a diet deficient in fruits and vegetables.
Macular Degeneration Symptoms
Symptoms are variable. The condition may not be noticeable in its early stages. Sometimes there is loss of vision in only one eye while vision remains good in the other eye for many years.
When both eyes are affected, the loss of central vision is usually noticed earlier. Some common ways visual loss is detected include:
- Words in the center of a page appear blurred
- A dark or blind spot appears in the center of vision
- Straight lines appear wavy or distorted
- Colors decrease in intensity or brightness
How is Macular Degeneration Diagnosed?
Many people do not realize that they have a macular problem until blurred vision becomes obvious. Your ophthalmologist can detect early stages of the disease during an eye examination by:
- Examining the macula at the slit lamp microscope.
- Performing a simple test in which you look at a grid resembling graph paper called an Amsler grid to determine if you see the grid lines as wavy or distorted.
- Taking special photographs after a dye is injected in the arm to locate abnormal blood vessels and fluid under the macula. This procedure is called Fluorescein Angiography.
- Performing an Optical Coherence Tomography (OCT) scan. An OCT scan provides high resolution cross sectional images of the retina to determine if there is fluid under the macula by showing its thickness, to look at the size and location of the yellowish drusen deposits and to look for scar tissue formation under the macula.
How is Macular Degeneration Treated?
Dr George Khouri is fellowship trained in retinal diseases which makes him very well versed in the diagnosis and treatment of macular degeneration.
Dry AMD Management
There is no treatment for dry AMD at this time. The Age-Related Eye Disease Studies (AREDS) which were conducted by the National Eye Institute, showed that a certain combination of nutritional supplements may slow or prevent the degenerative process. These include vitamins C and E, lutein, zeaxanthin, zinc and copper. Regular use of the Amsler grid helps patients detect the development of wet macular degeneration so they can seek care with the ophthalmologist immediately.
Wet AMD Treatment
Wet macular degeneration is treated with Intravitreal Injections of different medications, such as Avastin, Lucentis and Eylea which stop the growth of leaking abnormal blood vessels, known as neovascularization, causing a delay in progression and sometimes visual improvement. These medications block vascular endothelial growth factors (VEGF) which have been found to be responsible for growth of the abnormal blood vessels. Intravitreal injections may have to be repeated to be effective. Serial OCT scans are usually repeated to follow treatment progress. However, this treatment is not curative.
Despite the treatment available, some people with AMD still experience significant visual loss. A wide range of low-vision devices, support services, and rehabilitation programs are available to help these patients maintain a satisfying lifestyle.
To find out if you can benefit from the treatments available for macular degeneration, contact us today to make an appointment to see Dr George Khouri.
