Macular Degeneration Test

How We See February 8, 2006 When we view an object, light enters the cornea, the transparent, outer covering of the eye. The cornea bends the light, and the image passes through the lens to the retina, or light-sensitive membrane at the back of the eye. The retina acts like film in a camera. It contains specialized cells which detect the light impulses and translate them into electrical signals. The information is then sent through the optic nerve to the brain for processing. In the center of the retina is a small area, called the macula. The macula is responsible for seeing detailed, central, or straight-ahead, images (needed for tasks like reading and driving). Macular Degeneration Macular degeneration is a condition in which the cells in the macula begin to break down, or deteriorate. In early stages, words on a page are blurred and straight lines appear wavy. Distance vision becomes less clear and patients have a harder time distinguishing colors. As the condition progresses, a dark spot appears in the center of vision. The dark spot gradually enlarges until all central vision is lost. There are two forms of the disease. Dry macular degeneration is typically associated with aging and caused by a gradual thinning of the tissues in the macula and breakdown of the light-sensing cells. It is the most common form and tends to progress slowly. Wet macular degeneration occurs when new, abnormal blood vessels form under the retina. These blood vessels are fragile and can leak blood and fluid under the macula, damaging the cells in the macula. Wet macular degeneration is less common than the dry form, accounting for only about 10 percent of cases. However, this form progresses much more rapidly and can quickly cause a loss of central vision. According to the Macular Degeneration Foundation, about 12 million Americans have macular degeneration. Risk increases with age. The condition affects one in six people 55 to 64, one in four between 64 and 74 and one in three of those over 75. Women are more likely to be affected than men. The condition is also more common in whites and in smokers and those who have high blood pressure and/or a family history of the disease. Macular degeneration is the leading cause of vision loss in whites over 65. Annually, about 1.2 million people in the U.S. experience severe central vision loss from macular degeneration. About 200,000 lose all central vision in one or both or their eyes. Detecting Macular Degeneration Macular degeneration can usually be detected through an eye examination. A chart that looks like graph paper (called the Amsler grid) can be used to screen for the disease. In patients with macular degeneration, some of the lines on the chart may appear wavy. An eye care professional can also look at the back of the eye with a tool called an ophthalmoscope. Possible signs of macular degeneration include pigmentation changes in the retina or the appearance of deposits (called drusen). Special photographs of the eye can be used to detect abnormal or leaking blood vessels under the retina. Researchers at the University of Alabama at Birmingham are testing a new device that may help eye care professionals detect early signs of age-related macular degeneration. The device measures how quickly a patients eyes adapt from light to darkness. Studies show those who have difficulty adapting to darkness after light exposure are more likely to develop macular degeneration. Currently, doctors are still testing patients to develop a database of normal scores. Once they have established values of normal eyes versus those with potential or real disease, it will be easy to use the test to screen for macular degeneration risk. In fact, Greg Jackson, Ph.D., Ophthalmology Researcher, says the test may be able to detect macular degeneration as much as five to ten years earlier than current methods. The device may also be useful as a follow-up tool for patients who already have the disease, so doctors can monitor the effectiveness of treatments. Although the macular degeneration detection device is patented by University of Alabama researchers, the license to market the instrument has been given to Apeliotus Technologies of Atlanta. Researchers hope to have the device commercially available in the next two years. AUDIENCE INQUIRY For general information on macular degeneration, American Academy of Ophthalmology, public website, http://www.medem.com American Macular Degeneration Foundation, http://www.macular.org American Optometric Association, http://www.aoa.org Macular Degeneration Foundation, http://www.eyesight.org National Eye Institute, http://www.nei.nih.gov Prevent Blindness America, http://www.preventblindness.org BIBLIOGRAPHY "Adult Macular Degeneration," Henderson: Macular Degeneration Foundation, downloaded from website (http://www.eyesight.org), January 16, 2006. "Age-Related Disease Study Severity Scale and Simplified Severity Scale for Age-Related Macular Degeneration," Archives of Ophthalmology, November 2005, Vol. 123, No. 11, pp. 1598-1599. "The Age-Related Eye Disease Study Severity Scale for Age-Related Macular Degeneration," Archives of Ophthalmology, November 2005, Vol. 123, No. 11, pp. 1484-1498. 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Theodore, M.D., Ph.D., et al., "Automated Detection of Macular Drusen Using Geometric Background Leveling and Threshold Selection," Archives of Ophthalmology, February 2005, Vol. 123, No. 2, pp. 200-206. Zarbin, Marco, M.D., Ph.D., "Current Concepts in the Pathogenesis of Age-Related Macular Degeneration," Archives of Ophthalmology, April 2004, Vol. 122, No. 4, pp. 598-614. Research compiled and edited by Barbara J. Fister