Age‐related Macular Degeneration is a disease associated with aging that gradually destroys sharp, central vision. This condition is a leading cause of vision loss in Americans 60 years of age and older. Around 300,000 new cases of age‐ related macular degeneration occur each year. As much as 20% of age‐related macular degeneration (AMD) patients have one or more close relatives who also have the disease. AMD causes no pain, and in some cases, AMD advances so slowly that people notice little change in vision. In others, the disease progresses faster and may lead to a loss of vision in both eyes. The cause of macular degeneration is unknown and there is no cure for macular degeneration. The aim of treatment is to improve vision where possible and to stabilize the condition.
The retina is the light‐sensitive tissue located at the back of the eye. The retina instantly converts light, or an image, into electrical impulses. The retina then sends these impulses, or nerve signals, to the brain, which interprets what the eye is seeing. The macula is located in the center of the retina. The macula contains the highest concentration of cells that change light into nerve signals. The macula gives us center vision and allows us to see fine details. Center vision is needed for driving, reading, recognizing faces, and doing close work such as reading and sewing. When macular degeneration occurs, the nerve cells in the macula are damaged or disrupted and can't process images properly. When this happens, the patient loses center vision. Macular degeneration doesn't affect the patient's peripheral vision; therefore, they don't go completely blind. AMD occurs in two forms: wet and dry.
Dry AMD accounts for 90% of the cases of macular degeneration. It is produced by the aging and thinning of the retinal tissues at the back of the eye, which causes light sensitive cells to break down. Dry AMD develops slowly with mild vision loss occurring. The patient may experience only a slight dimming or blurring of central vision. As dry AMD gets worse, a blurred spot may appear in the center of the visual field. Gradually, as less of the macula functions, central vision is lost in the affected eye.
The most common symptom of dry AMD is slightly blurred vision. The patient may have difficulty recognizing faces. They may need more light for reading and other tasks. Dry AMD generally affects both eyes, but vision can be lost in one eye while the other eye seems unaffected. One of the most common early signs of dry AMD is drusen.
Drusen are yellow deposits under the retina. They often are found in people over age 60. Your eye care professional can detect drusen during a comprehensive eye exam. Drusen alone do not usually cause vision loss. In fact, scientists are unclear about the connection between drusen and AMD. However, when an increase in the size or number of drusen occurs, the person's risk of developing either advanced dry AMD or wet AMD also increases. These changes can cause serious vision loss.
Dry AMD has three stages, all of which may occur in one or both eyes:
Early AMD: People with early AMD have either several small drusen or a few medium‐sized drusen. At this stage, there are no symptoms and no vision loss.
Intermediate AMD: People with intermediate AMD have either many medium‐sized drusen or one or more large drusen. Some people see a blurred spot in the center of their vision. More light may be needed for reading and other tasks.
Advanced Dry AMD: In addition to drusen, people with advanced dry AMD have a breakdown of light‐sensitive cells and supporting tissue in the central retinal area. This breakdown can cause a blurred spot in the center of your vision. Over time, the blurred spot may get bigger and darker, taking more of your central vision. You may have difficulty reading or recognizing faces until they are very close to you.
No cure is available for dry macular degeneration. When a patient loses vision from dry AMD in one eye only, they may not notice any changes in overall vision. With the other eye seeing clearly, they can drive, read, and see fine details. They may notice changes in vision only if AMD affects both eyes. While dry AMD can advance and cause vision loss without turning into the wet form, this form also can suddenly turn into the wet form, even during its early stage. There is no way to tell if or when the dry form will turn into the wet form. If the fovea, or center of the macula, is affected, vision may be reduced significantly. If not, vision may remain good for a long time. Always see an eye care professional for a comprehensive eye exam when experiencing blurry vision.
Wet AMD makes up 10% of all cases of macular degeneration, and is a much greater threat to a person's vision than dry AMD. It affects about 20% of people over age seventy‐five. Wet AMD is the cause of 90% of all cases of legal blindness. Wet AMD is considered an advanced stage form of AMD. It occurs when new abnormal blood vessels begin to form, first under the retina. The effect is similar to tree roots growing under a sidewalk. The blood vessels force the retina away from the eyeball causing distortions of vision such as straight lines appearing wavy. This early warning sign of Wet AMD should not be ignored. The newly formed blood vessels are generally very fragile and often leak blood and fluid. The blood and fluid raise the macula from its normal place at the back of the eye, damaging the macula rapidly, and causing a large blind spot to occur.
Leakage can also develop under the retina causing a blister to form. The leakage may or may not be caused by abnormal blood vessels. If no blood vessels are present, the blister is usually left untreated. The blister may cause some vision impairment, but most of the patient's vision will remain. If the blister is invaded by blood vessels, it is called a neovascular membrane. When this happens, if treatment doesn't take place, the macula can become damaged and vision loss can occur due to the leaking blood vessels.
With wet AMD, loss of central vision may occur quickly. Wet AMD is also known as advanced AMD. It does not have stages like dry AMD. An important early symptom of wet AMD is that straight lines appear wavy. Anyone noticing this condition or other changes in vision should contact an eye care professional at once for a comprehensive eye exam.
Can advanced AMD be either the dry form or the wet form?
Yes. Both the wet form and the advanced dry form are considered advanced AMD. Vision loss occurs with either form. In most cases, only advanced AMD can cause vision loss. People who have advanced AMD in one eye are at especially high risk of developing advanced AMD in the other eye.
Macular Degeneration Risk Factors
The greatest risk factor for AMD is age. Although AMD may occur during middle age, studies show that people over age 60 are clearly at greater risk than other age groups. For instance, a large study found that people over 50 years of age have about a 2% risk of getting AMD, while people over 75 have about a 30% chance of getting the disease.
Other risk factors may include:
Heredity. 20% of AMD patients have one or more close relatives who also have AMD
Long‐term exposure to light, especially blue or ultra‐violet light may increase the risk of AMD
People with light‐colored eyes are at a greater risk than those with dark‐colored eyes
Caucasians are more likely to develop AMD than African‐Americans
Women are at a greater risk than men.
Obesity has been linked to the progression of early and intermediate stage AMD to advanced AMD.
People who have low blood levels of antioxidant vitamins such as A, C, and E
People who have low levels of minerals such as zinc.
High cholesterol levels
Smokers are 2.5 times more likely to develop AMD than non‐smokers.
Beer consumption may be associated with increased risk of wet macular degeneration.
Symptoms of Macular Degeneration
One of the earliest signs of age‐related macular degeneration that can only be observed by an eye care professional is the development of drusen, which are small yellow deposits under the macula. They are common in people over age fifty. Drusen don't usually cause a major decrease in a person's vision, but may indicate a future development of macular degeneration and loss of center vision. Both dry and wet AMD cause no pain.
The most common early sign of Dry AMD is blurred vision, grayness, haziness, and a blind spot in the center of the field of vision. The patient may also notice blurred words when reading or sense that colors are dimmer. Some people notice a change in their vision only if macular degeneration affects both eyes. As fewer cells in the macula are able to function, details appear less clearly, such as faces or words in a book. Often this blurred vision will go away in brighter light. As the loss of these light‐sensing cells progresses, people may see a small‐‐but growing‐‐blind spot in the middle of their field of vision.
The common early symptom of wet AMD is that lines that should be straight appear wavy or crooked, such as sentences on a page or the straight edge of a table or building. This results when fluid from the leaking blood vessels gathers and lifts the macula, distorting vision. Dark or empty areas called blind spots may appear in the center of the patient's vision. The blind spots are usually black or gray when the blood vessels first begin leaking. Later, as scar tissue forms, the spots appear gray or white.
Testing for Macular Degeneration
There are a number of tests that can be done to check for macular degeneration. The Amsler grid is a simple test people can do at home. The Amsler grid has a pattern resembling a checkerboard with a dot in the center. The person covers one eye at a time and looks at the dot. If the straight lines appear wavy, or if they are missing, the person may be suffering from wet macular degeneration and should call an ophthalmologist immediately.
During the comprehensive eye exam the ophthalmologist will usually start with a simple visual acuity test and then dilate the patient's pupil and look at the retina. A special magnifying lens is used to examine the retina and optic nerve for signs of AMD and other eye problems. The presence of drusen in the retina indicates the eye may be at risk for developing macular degeneration. The ophthalmologist may also be able to see abnormal blood vessels or signs of leaking vessels at this time. The patient may be asked to look at an Amsler grid. The eye doctor may also use a tonometer; an instrument that measures the pressure inside the eye. Other tests may be conducted to learn more about the structure and health of the patient’s eye.
If the eye care professional believes treatment is needed (s) he may request a fluorescein angiography, which detects leaky blood vessels under the retina. In this test, fluorescent dye is injected into a vein in the arm. Eye Images are taken as the dye passes through the blood vessels of the eye. The images are used to evaluate leaking blood vessels and to determine how they should be treated.
Macular Degeneration Treatments
Once dry AMD reaches the advanced stage, no form of treatment can prevent vision loss. However, early treatment can delay and possibly prevent intermediate AMD from progressing to the advanced stage, in which vision loss occurs. The National Eye Institute's Age-Related Eye Disease Study (AREDS) found that taking a specific high‐dose formulation of vitamin and antioxidants along with zinc such as is found in Ocu‐Vite and I‐Caps AREDS formula does have protective effects on the retina in persons with early to moderate AMD, and significantly slows the progression from the intermediate to the advanced stage AMD and its associated vision loss. People who are at high risk for developing advanced AMD should consider taking the formulation. The AREDS formulation is not a cure for AMD. It will not restore vision already lost to the disease. However, it may delay the onset of advanced AMD. It may help save the vision of many people who are at high risk for developing advanced AMD to keep their vision.
Wet AMD can be treated with laser surgery, photodynamic therapy, and injections into the eye. None of these treatments is a cure for wet AMD. The disease and loss of vision may progress despite treatment.
Laser Photocoagulation Surgery: Used in severe cases, this procedure works best when the blood vessels have not grown under the macula or near the fovea (the central part of the macula). This procedure uses a high energy laser beam to destroy the fragile, leaky blood vessels. However, laser treatment may also destroy some surrounding healthy tissue and some vision. Only a small percentage of people with wet AMD can be treated with laser photocoagulation surgery. The risk of new blood vessels developing after laser treatment is high. Repeated treatments may be necessary. In some cases, vision loss may progress despite repeated treatments.
Photodynamic Therapy: Photodynamic therapy is a relatively painless procedure that takes about 20 minutes and can be performed in a doctor's office. Photodynamic therapy slows the rate of vision loss. It does not stop vision loss or restore vision already lost to wet AMD. As with other treatments for AMD, results are often temporary and may need to be repeated. During this procedure, a drug called verteporfin is injected into the patient’s arm. It travels throughout the body, including the new blood vessels in the eye. The drug tends to "stick" to the surface of new blood vessels. Next, a light is shined into the eye for about 90 seconds. The light activates the drug, which destroys the new blood vessels and slows the rate of vision loss. Unlike laser surgery, this drug does not destroy surrounding healthy tissue. Because the drug is activated by light, you must avoid exposing your skin or eyes to direct sunlight or bright indoor light for five days after treatment.
Injections: Wet AMD can now be treated with new drugs that are injected into the eye (anti‐VEGF therapy). Abnormally high levels of a specific growth factor occur in eyes with wet AMD and promote the growth of abnormal new blood vessels. This drug treatment blocks the effects of the growth factor. This treatment requires multiple injections that may be given as often as monthly. The eye is numbed before each injection.
After the injection, you will remain in the doctor's office for a while and your eye will be monitored. This drug treatment can help slow down vision loss from AMD and in some cases improve sight.
Age‐Related Eye Disease Study (AREDS)
The National Eye Institute's Age-Related Eye Disease Study (AREDS) found that taking a specific high‐dose formulation of vitamin and antioxidants along with zinc such as is found in Ocu‐Vite and I‐Caps AREDS formula does have protective effects on the retina in persons with early to moderate AMD, and significantly slows the progression from the intermediate to the advanced stage AMD and its associated vision loss. People who are at high risk for developing advanced AMD should consider taking the formulation. The AREDS formulation is not a cure for AMD. It will not restore vision already lost to the disease. However, it may delay the onset of advanced AMD. It may help save the vision of many people who are at high risk for developing advanced AMD to keep their vision. During the early stage AMD, a comprehensive eye exam every year can help monitor the disease and its progression. If early stage AMD progresses to the intermediate stage, taking the formulation should be discussed with the doctor.
The high levels of vitamins and minerals are difficult to achieve from diet alone. However, previous studies have suggested that people who have diets rich in green leafy vegetables have a lower risk of developing AMD. The formulation's levels of antioxidants and zinc are also considerably higher than the amounts in any daily multi‐vitamin. Patients should be sure to review all currently used vitamin supplements with the physician before starting the AREDS regimen. Because multivitamins contain many important vitamins not found in the AREDS formulation, you may want to take a multivitamin along with the AREDS formulation. For example, people with osteoporosis need to be particularly concerned about taking vitamin D, which is not in the AREDS formulation.
Preventing Vision Loss
The key to preventing vision loss from macular degeneration is early detection. Everyone should get regular eye checkups, especially if macular degeneration runs in their family. Patients at high risk can also use the Amsler grid on a regular basis to check for signs and symptoms of macular degeneration. If a person develops macular degeneration in one eye, the other eye has a 60% chance of developing macular degeneration within five years. These patients should be particularly vigilant about using the Amsler grid regularly and scheduling routine visits with their eye doctor. Another thing people can do to prevent macular degeneration is to maintain a healthy weight and lifestyle, including a balanced diet with plenty of green leafy vegetables to ensure they get the vitamins and minerals needed for healthy eyes, wearing sunglasses that protect against harmful ultraviolet light, and avoiding smoking. See an ophthalmologist immediately to report any changes in vision.
Low vision is vision loss that cannot be corrected by ordinary glasses, contact lenses, medication or surgery. People with low vision usually retain some usable vision. An ophthalmologist or optometrist specializing in low vision can evaluate a patient’s vision and prescribe optical devices to maximize remaining vision. This functional vision assessment is an important step in helping improve an AMD patient’s quality of life. Low vision aids can help the macular degeneration patient perform daily activities. These aids usually involve a combination of magnification and bright lights. The devices, which are stronger than regular eyeglasses, include telescopic glasses, lenses that filter light, and magnifying glasses. Electronic devices that can be held in the hand or put directly on reading material are also available. Non‐optical devices such as large‐print clocks and remote controls, as well as signature and writing guides, are also popular. Vision rehabilitation services equip patients with skills and strategies to help them remain safe, independent and active as the disease progresses.
These services are provided by a multidisciplinary team of professionals who can introduce the patient to new methods of using remaining vision to maximize daily functionality and adjust to vision loss. This team includes specially trained ophthalmologists, optometrists, social workers, nurses, occupational therapists, vision rehabilitation therapists, career counselors, orientation and mobility specialists and others.