Macular Degeneration Evaluation

The macula is the central part of the retina. While the macula makes up only a small part of the retina, it is the area that is responsible for fine vision, such as reading small print and street signs. The rest of the retina, referred to as the peripheral retina, is responsible for peripheral vision and is not nearly as sensitive to detail as the macula.

Age-related macular degeneration (AMD) is a deterioration or breakdown of the eye’s macula that most often occurs as part of the body’s natural aging process. While other disease processes can affect the macula, AMD is the most common. The macula is a small area in the retina—the light-sensitive tissue lining the back of the eye. The macula is the part of the retina that is responsible for central vision. This allows people to see fine details clearly.

There are two forms of AMD: dry or atrophic AMD and wet AMD. Dry AMD is by far the most common form and is generally less severe. It is important to know that most people who are diagnosed with early macular degeneration do not go on to lose significant vision from the disease. AMD very rarely causes complete loss of vision. When AMD does cause vision loss, it usually starts in just one eye, although it may affect the other eye later. In addition, macular degeneration does not affect the peripheral retina. Even patients with advanced disease generally keep their peripheral vision.

Many people do not know that they have macular degeneration until they have a noticeable vision problem or until it is detected during an eye examination. This is especially common if only one eye is affected. To check for macular degeneration, Dr. Callahan will dilate your pupils using eye drops. This is the only way to have a clear and detailed view of the retina. If you have signs of AMD, Dr. Callahan may recommend monitoring with an Amsler grid, vitamin supplements, or more frequent follow up. If there is evidence that you have wet AMD, Dr. Callahan will most likely refer you to a retina specialist for further evaluation and treatment.

Video: Macular Degeneration

This video explains the role of the macula and how macular degeneration can cause loss of central vision. Both dry and Wet AMD are discussed, along with a number of treatment options such as nutritional supplements, laser therapy and injections.

Risk Factors for Macular Degeneration
  • Genetics: Recent research shows that genetic changes are responsible for about 50 percent of all AMD
  • Age: The risk of developing AMD increases with each decade of life, especially after 60
  • Smoking
  • Hypertension and high cholesterol: As our understanding of AMD evolves, it is thought to be a vascular disease. Risk factors for cardiovascular disease are also likely risk factors for AMD. In other words, what is good for your heart is probably good for your eyes too.
Dry Macular Degeneration

Aging and thinning of the macula cause dry AMD. It usually begins with small yellow deposits called drusen that form under the macula. Eventually the macula may become too thin to function properly. The vision changes from dry macular degeneration usually develop gradually and include the following:

  • Blurry distance and/or reading vision
  • Need for increasingly bright light to see up close
  • Colors appear less vivid or bright
  • Hazy vision
  • Difficulty seeing when going from bright light to low light (such as entering a dimly lit room from the bright outdoors)
  • Trouble or inability to recognize people’s faces
  • Blank or blurry spot in your central vision

The Amsler grid is a useful tool for detecting subtle vision changes particularly in patients with dry AMD. The figures below illustrate both a normal Amsler grid and a part of a distorted Amsler grid such as it might appear to a patient with AMD. Dr. Callahan will give you detailed instructions for use of this tool. If you notice any change in your central vision you should contact Dr. Callahan or your retina specialist as soon as possible. This is important because it can be in indication that the dry form of AMD has changed into the more damaging wet form of the disease.

Click here to view a Macular Degeneration simulator

Dry Macular Degeneration Treatment

While there is currently no treatment for dry AMD, there is a lot of research in this area. The key is detecting any change from the dry to the wet form as soon as possible in order to minimize subsequent damage to the retina.

Patients who meet certain criteria may benefit from vitamin supplements. The best study on this is the Age-Related Eye Disease Study (AREDS). This study shows that taking certain vitamin supplements decreases the risk of progression to advanced AMD in certain groups of patients at high risk (such as patients with a large amount of drusen or those with significant vision loss in at least one eye). Taking vitamin supplements has not been shown to provide a benefit for those without AMD or with minimal AMD.

Other studies have shown that eating dark leafy greens, as well as other colorful fruits and vegetables rich in lutein and zeaxanthin, may reduce your risk for developing macular degeneration. Again, if it is good for your heart it is probably good for your eyes too.

The following is the nutrient supplementation shown to be beneficial in lowering the risk of macular degeneration progressing to advanced stages (the AREDS formulation):

  • Vitamin C – 500 mg
  • Vitamin E – 400 IU
  • Beta-carotene – 15 mg (Beta carotene has been shown to increase the risk of lung cancer in smokers or recent past smokers, so this supplement should not be used by people who currently smoke or recently quit smoking.)
  • Zinc oxide – 80 mg
  • Copper (as cupric oxide) – 2 mg (to prevent copper deficiency, which may be associated with taking high amounts of zinc)

The Age-Related Eye Disease Study 2 (AREDS2) evaluated the effects of oral supplementation of macular xanthophylls (lutein and zeaxanthin) and/or long-chain omega-3 fatty acids on the progression to advanced (AMD). An additional goal of the study was to assess whether forms of the AREDS nutritional supplements with reduced zinc and/or no beta-carotene works as well as the original supplement in reducing the risk. Other studies have looked at folic acid, vitamins B6 and B12. To date, the AREDS formulation is the only treatment known to reduce the risk of progression to advanced AMD.

It is very important to remember that vitamin supplements are not a cure for macular degeneration. They not will restore the vision already lost from the disease. However, specific amounts of these supplements do play a key role in helping some people at high risk for developing advanced (wet) AMD to maintain their vision. Dr. Callahan will discuss with you whether vitamin supplements may be helpful.

Wet Macular Degeneration

Only about 10 percent of patients with AMD have the wet or exudative form (also referred to as the neovascular form) of the disease. It generally causes more vision loss than dry AMD. Wet macular degeneration symptoms usually appear and get worse fairly quickly. They include:

  • Distorted vision — straight lines will appear bent, crooked or irregular
  • Dark gray spots or blank spots in your vision
  • Loss of central vision
  • Size of objects may appear different for each eye
  • Colors lose their brightness; colors do not look the same for each eye

People who are at risk for macular degeneration should have regular eye exams by Dr. Callahan and, if diagnosed, begin treatment as indicated.

Wet macular degeneration occurs when abnormal blood vessels begin to grow underneath the retina. These blood vessels grow from the vascular layer under the retina called the choroid and are referred to as choroidal neovascularization or CNV. These new blood vessels may leak fluid or blood, blurring or distorting central vision. The more extensive the bleeding and leakage are, the greater the risk of central vision loss.

The earlier that wet AMD is diagnosed and treated, the better chance of keeping central vision. While this process usually occurs in one eye at a time, the other eye is at risk for similar changes and must be monitored closely.

Wet AMD Treatment

There is a great deal of research in this area, and new drugs are continually being developed. There are several treatment modalities currently used to treat wet AMD. Successful treatment depends on early detection. Treatment generally reduces the risk of severe vision loss but does not eliminate it completely. If you have any evidence of wet AMD, Dr. Callahan will refer you to a retina specialist for treatment.

Injections

Because the underlying problem in wet AMD is the formation of abnormal blood vessels under the retina, current treatments focus on targeting the chemicals in the body that cause blood vessel growth. The main target is VEGF (Veg F) or vascular endothelial growth factor. Drugs such as Avastin, Lucentis and Eyelea (VEGF inhibitors) are injected directly into the back of the eye where they reduce the growth of abnormal blood vessels and slow their leakage. This can help to slow vision loss and in some cases improve vision.

VEGF injections are done by a retina specialist and often must be repeated over the course of many months for continued benefit. In some cases, Dr. Callahan may recommend combining anti-VEGF treatment with other therapies.

Laser

Another form of treatment for wet AMD is laser therapy. The laser is used to destroy the abnormal blood vessels in order to prevent further growth, leakage and bleeding. Following laser treatment, vision may be more blurred than before treatment but will often stabilize within a few weeks. A scar forms where the treatment occurred, creating a permanent blind spot that might be noticeable in your field of vision. Usually the abnormal blood vessels are destroyed by laser treatment. However, it is likely that 50 percent of patients with wet macular degeneration who receive this laser procedure will need a re-treatment within three to five years.

What Happens When Macular Degeneration Cannot Be Treated?

It is important to remember that only about 10 percent of all macular degeneration cases are the wet form, many of which cannot be treated. AMD very rarely causes complete blindness. People with wet or dry AMD will almost always keep their peripheral vision.

Even when there is little that can be done to improve the eyesight of someone who has AMD, we can make the most of your remaining vision with the help of special low-vision rehabilitation, devices and services. People with low vision can learn new strategies to accomplish daily activities. These skills, including mastering new techniques and devices, help people with advanced AMD regain their confidence and live independently despite loss of central vision.

Early detection of AMD and close monitoring by both the patient and Dr. Callahan for signs of progression are the absolute best ways to maintain good vision.