Macular degeneration (also called age related macular degeneration or AMD) is the leading cause of impaired reading or detailed vision. It is caused by the breakdown of the macula, the central portion of the retina. Although macular degeneration causes distortion of central and color vision, side vision is not affected.
What is the retina? The retina is the thin layer of light-sensitive tissue which serves as the inner lining of the eye. When light enters the eye, it is focused by the cornea and the lens onto the retina. The retinathen transforms the light images into electrical impulses which are sent to the brain through the optic nerve.
What is the macula? The macula is a very small area of the retina which is responsible for central vision and color vision. The macula allows us to read, drive, and perform detailed work. Surrounding the macula is the peripheral retina which is responsible for side vision and night vision.
What causes macular degeneration? Macular degeneration is most commonly a natural result of the aging process. With time, the retinal tissues break down, causing a loss of function of the macula. Smoking, obesity, high blood pressure, family history and poor diet are known to increase the risk of developing AMD.
90% of AMD patients only have early or dry AMD. However, about 10% of the cases develop into wet AMD where aging of the retina is compounded by leakage of the tiny blood vessels which nourish the retina. Growth of new, abnormal blood vessels in the scar tissue that forms from the leaking blood vessels occurs. The abnormal vessel, leak blood and fluid which destroy the macula and together with the dense scar tissue cause central vision to become blocked, distorted and blurred. Occasionally, macular degeneration is caused by injury, infection or inflammation.
What are the symptoms of macular degeneration? The most notable symptom of macular degeneration is blurry or distorted central vision. Difficulty in reading, doing close work, or driving may also be noticed. A person with macular degeneration may experience blurry words on a page, distortion of the center of a scene, a dark or empty area in the center of vision or the distortion of lines.
Macular degeneration may also cause a dimming of color vision. Fortunately, the disease does not cause total blindness, as side vision is not affected. Macular degeneration only affects central and color vision. However, if macular degeneration occurs in only one eye, the symptoms of the disease may not be notices, as the “good” eye compensates for the “bad” eye.
How is macular degeneration diagnosed? A lighted instrument called an ophthalmoscope is used to examine the retina. The appearance, size and quantity of drusen may be an indication of AMD. In addition, some special tests may be administered. The Amsler Grid test, in which the patient looks at a page similar to graph paper, is used to detect blind spots or distortion of central vision. A color vision test will indicated damage to the macula if the patient cannot detect symbols or letters camouflaged in colored patterns.
If macular degeneration is detected, a procedure called flourescein angiography may be done to check for blood vessel leakage. A dye, which quickly travels to the eye, is injected into the patient’s arm. Photographs of the blood vessels in the retina are then taken to determine the extent of the damage. Other imaging techniques like optical coherence tomography (OCT) can be used to aid in diagnosis or monitoring the progression of AMD.
How is macular degeneration treated? Unfortunately, there is no cure for macular degeneration. However, a healthy lifestyle can be important in reducing the risk of developing AMD. A healthy diet rich in green leafy vegetables and fish, supplemented with vitamins high in specific antioxidants (A, C, E and beta-carotene with zinc), can significantly reduce the risk of advanced AMD and its associated vision loss.
Laser treatments can seal leaky blood vessels to reduce hemorrhaging and scarring that decrease central vision.
Recent research shows the presence of vascular endothelial growth factor type A (VEGF-A) stimulates the growth of blood vessels in patients with wet AMD. The presence of these new abnormal blood vessels impairs vision. New anti-VEGF-A medication regimens, like Lucentis, Macugen and Avastin, inhibit VEGF-A, reduce new vessel growth and result in improved vision.
Low Vision Aids:
People who suffer from macular degeneration are able to compensate for some of their vision loss through the use of low vision aids. May sophisticated magnifying devices, as well as spectacles and hand or stand magnifiers, are available. Bright illumination for reading and other close work can also be helpful.