What is the Retina?
The retina is a light-sensitive tissue lining the back of the eye containing cells that are sensitive to light and that trigger nerve impulses that pass via the optic nerve to the brain, where a visual image is formed. The retina is considered part of the central nervous system (CNS) and is actually brain tissue. It is composed of many layers, all of which have specific functions. It contains photoreceptor cells called rods and cones. Rods aid in night vision and seeing black and white hues, whereas cones aid in daytime vision and seeing colors. The retina also contains the macula which helps in central vision and the optic disc, an area where the optic fibers leave the eye and go to the brain.
How Does it Work?
The retina acts like the film in a camera. The image is processed to the retina where it is then transmitted to the brain via the optic nerve. The photoreceptor nerve cells of the retina change the light rays into electrical impulses and send them through the optic nerve to the brain where an image is perceived. The center ten percent of the retina is called the macula. This is responsible for your sharp central vision. The peripheral retina is responsible for the peripheral vision. As with the camera, if the “film” is bad in the eye (i.e. the retina), no matter how good the rest of the eye is, you will not get a good picture.
Macular degeneration is a deterioration or breakdown of the macula. The disease breaks down the macula, the light-sensitive part of the retina responsible for the sharp, direct vision needed to read or drive. When the macula does not function correctly, your central vision can be affected by blurriness, dark areas or distortion.
Facts about Macular Degeneration
- Macular degeneration is the leading cause of blindness in people over the age of 55. Legal blindness is defined as 20/200 vision or less with eyeglasses.
- Seventy percent of patients have the “dry” form, which involves thinning of the macular tissues and disturbances in its pigmentation.
- Thirty percent have the “wet” form, which can involve bleeding within and beneath the retina, opaque deposits, and eventually scar tissue.
- The “wet” form accounts for ninety percent of all cases of legal blindness in macular degeneration patients.
- Many older people develop macular degeneration as part of the body’s natural aging process.
- Any type of smoking or exposure to tobacco smoke can accelerate the development of the “wet” type of macular degeneration.
- The following are NOT known to be linked to macular degeneration: floaters (moving spots caused by debris floating in the vitreous fluid between the lens and the retina); dry eye syndromes; cataracts and cataract surgery.
- Macular degeneration appears to be hereditary in some families but not in others. Since macular degeneration affects most patients later in life, it is difficult to study successive generations in a family.
What causes Macular Degeneration?
The root causes of macular degeneration are still unknown. There are two forms of age-related macular degeneration, “wet” (AMD) and “dry”:
- “Dry” macular degeneration (atrophic) — Most people have the “dry” form of AMD. It is caused by aging and thinning of tissues of the macula. Vision loss is usually gradual.
- “Wet” Macular Degeneration (exudative) — The “wet” form of macular degeneration accounts for about 10% of all AMD cases. It results when abnormal blood vessels form underneath the retina 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.
What are the symptoms of Macular Degeneration?
Macular degeneration can cause different symptoms in different people. The condition may be hardly noticeable in its early stages. Declining vision noticed by the patient or by an ophthalmologist during a routine eye exam may be the first indicator of macular degeneration. The formation of new blood vessels exudates, or “drusen,” from blood vessels in and under the macula is often the first physical sign that macular degeneration may develop. Anyone experiencing the following symptoms should consult an ophthalmologist immediately: Straight lines appear distorted and, in some cases, the center of vision appears more distorted than the rest of the scene. A dark, blurry area or “white-out” appears in the center of vision. Color perception changes or diminishes.
Is there a cure for Macular Degeneration?
At this time there is no known cure for macular degeneration, but treatment may be able to delay its progression or even improve your vision. In some cases, macular degeneration may be active and then slow down considerably, or even stop progressing for many years. One day, research may show us how to prevent and reverse the disease. Today, there are ways to arrest macular degeneration, depending on the type and degree of the condition. These range from nutritional intervention, to laser surgery of the blood vessels. We have also developed low vision aids and techniques for maximizing the use of peripheral vision to help patients adapt better to their loss of central vision. Educating susceptible groups about macular degeneration can enhance early detection and early treatment.
Can diet and/or supplements treat Macular Degeneration?
Some scientists have suggested an association between macular degeneration and high saturated fat, low carotenoid pigments, and other substances in the diet. There is evidence that eating fresh fruits and dark green, leafy vegetables (such as spinach and collard greens) may delay or reduce the severity of age-related macular degeneration. Taking anti-oxidants like vitamins C and E may also have positive effects.
It is very important to remember that vitamin supplements are not a cure for AMD, nor will they restore vision that you may have already lost from the disease. However, specific amounts of these supplements do play a key role in helping some people at high risk for advanced AMD to maintain their vision. You should speak with your ophthalmologist to determine if you are at risk for developing advanced AMD, and to learn if supplements are recommended for you.
What treatments are available for Macular Degeneration?
Certain types of “wet” macular degeneration can be treated with laser surgery, a brief outpatient procedure. Laser surgery and another form of treatment called photodynamic therapy use a focused beam of light to slow or stop leaking blood vessels that damage the macula. These procedures may preserve more sight over all, though they are not cures that restore vision to normal. However, despite advanced medical treatment, many people with macular degeneration still experience some vision loss.
Is there anything that worsens Macular Degeneration?
It has been demonstrated that the blue rays of the spectrum seem to accelerate macular degeneration more than other rays of the spectrum. This means that very bright light, such as sunlight or its reflection in the ocean and desert, may worsen macular degeneration. Special sunglasses that block out the blue end of the spectrum may decrease the progression of the disease. However, more research is needed in this area.
Hypertension tends to make some forms of macular degeneration worse, especially in the “wet” form where the retinal tissues are invaded by new blood vessels. The medications used to treat hypertension have not been shown to have any direct effect on macular degeneration, but they may slow the progression of the disease by reducing hypertension.
Please contact the Nielsen Eye Center at 617-471-5665 for information regarding the treatment for macular degeneration. Patient Advocates at our offices south of Boston including Quincy, Weymouth and Norwell and other Massachusetts-area locations can help.