Macular degeneration is a disease of the macula, an area of the retina located at the back of the eye that is responsible for fine detail vision. Generally, vision loss is gradual and affects both eyes at different rates. Even with a loss of central vision, color vision and peripheral vision may remain unaffected.
The early stages of macular degeneration may cause little if any noticeable change in vision. Gradually, reading without extra light and magnification becomes difficult. Vision can become distorted. As it progresses, it becomes difficult to see details in the center field of vision. There are two forms of age-related macular degeneration, wet and dry.
Wet macular degeneration occurs when abnormal or leaking blood vessels develop under the retina in the area of the macula. The leaking vessels produce distorted or blurred vision and at times, a rapid and severe loss of central vision.
Dry macular degeneration is the most commonly diagnosed form of the disease. Dry macular degeneration occurs when there is thinning or deterioration of the macula tissue or the formation of abnormal yellow deposits called drusen. This form of the disease progresses very slowly and does not always affect both eyes equally.
Although the root causes of macular degeneration are still unknown, studies show that gender and race can be factors. Women are at a slightly higher risk to develop macular degeneration than men, and Caucasians are more likely to develop the disease than African Americans. Other risk factors include:
- Age (Macular degeneration is the leading cause of decreased vision in people over 65 years of age.)
- Heredity (Macular degeneration can be hereditary in some families but not in others.)
- Extended sun exposure
- High blood pressure
- High cholesterol
- Nutritional deficiencies
- Head trauma
Drs. Baker and Slade use various instruments during an exam to identify changes in the macula. Subtle changes in vision can also be detected using the Amsler Grid. While staring at the dot in the middle of the grid, patients with macular degeneration may see wavy or warped lines, instead of horizontal and vertical lines.
Angiography is the most commonly used diagnostic test for macular degeneration diagnostic. This test entails injecting a harmless orange-red dye, called fluorescein, into a vein in the arm. The dye travels throughout the body and into the blood vessels in the retina. Next, a special camera takes multiple photographs of the retina. Finally, the pictures are analyzed to identify damage to the retina lining or newly formed atypical blood vessels. The formation of new blood vessels from blood vessels in and under the macula is often the first physical sign that macular degeneration may develop.
Optical Coherence Tomography (OCT) creates a contour map of the retina using light rays. This map may show areas of thickening or fluid accumulation.
Treatments for Macular Degeneration
Regular eye exams, good nutrition, in-home monitoring of vision and possibly dietary supplements may be all that is recommended during the early stages of macular degeneration.
Recent studies on the use of vitamins and antioxidants to prevent or slow the progression of macular degeneration indicate that people who have diets high in lutein and zeaxanthin may have a lower risk of developing macular degeneration. Antioxidants are thought to protect against the damaging effects of free-radicals, oxygen-charged molecules. A key group of antioxidants is called carotenoids. Carotenoids are pigments that give fruits and vegetables their color. Lutein and zeaxanthin are two carotenoids that occur naturally in the macula of the eye. Vegetables including kale, raw spinach, and collard greens have the highest lutein and zeaxanthin content. Nutritional supplements that are high in lutein, zeaxanthin, and other antioxidants are also available.
Low Vision Aids
While dry macular degeneration is not treatable, a small percentage of wet macular degeneration can be treated. Low vision aids such as handheld magnifying glasses or more sophisticated video cameras that enlarge print may help make it easier to live with the decreased vision of dry macular degeneration. Lifestyle aids such as large print books, tape-recorded books or magazines, large print playing cards, talking clocks and scales, and many other devices are available. Currently, an implantable mini-telescope is in its final stages of clinic trials. These mini-telescopes have shown great promise for patients who have lost all use of their central vision.
LUCENTIS and Macugen are relatively new treatments for the wet form of age-related macular degeneration. These injections prevent abnormal blood vessel growth and leakage.
Laser treatment may also be used in some cases of wet macular degeneration. This form of treatment is only possible when the abnormal blood vessels are far enough away from the macula that it will not damage it. Only rare cases of wet macular degeneration meet these criteria. This treatment involves using painless laser light to destroy abnormal, leaking blood vessels under the retina. When laser treatment is possible, it may slow or stop the progression of the disease but is generally not expected to restore vision loss.
Some cases of wet macular degeneration can be treated with photodynamic therapy or PDT. In those cases where PDT is appropriate, slowing the progression of vision-loss and improvement in vision is possible.