Macular degeneration (or age-related macular degeneration, abbreviated AMD) is the leading cause of vision loss in the Western world. The disease affects the retina, the light-sensitive layer of tissue at the back of the eye. This layer has photo-receptors that are stimulated by light and send signals to your brain, thereby generating vision. Specifically, AMD affects the central part of the retina called the macula and this is the portion of your eye that is used when engaging in visual activities that require the finest acuities, such as reading and driving. Macular degeneration occurs in either a dry (atrophic) or wet (exudative) form. In either case, the disease only affects the central vision, typically near the macula, and rarely causes total vision loss.
Normal Macular Degeneration
The majority of patients (over 80% of AMD cases) have the dry or atrophic type of macular degeneration. In this form of the disease, the slow deterioration of the retina is coincidental with the formation of small yellow deposits, known as drusen, in the macular region. This accumulation of drusen leads to a thinning of the macular tissues, causing distortions in vision that initially appear as wavelike. The eventual amount of central vision loss is directly related to the location and amount of retinal thinning caused by the drusen.
The exudative, or wet form of the disease, is far less common (about 20% of AMD cases), but it is more aggressive and threatening to one’s vision. In the wet type of macular degeneration, abnormal blood vessels grow under the retina and macula through a process called neovascularization. These new blood vessels may bleed and leak fluid, thereby causing the macula to bulge or lift up, distorting or destroying central vision. In these circumstances, vision loss may be rapid and severe.
Although much research is being done on finding treatments for macular degeneration, no current treatment exists for the more common dry form, and the treatment for the wet form sometimes does not meet patients expectations. So, for many AMD patients, the use of low vision aids for macular degeneration is of great help and allows them to enhance their quality of life and remain independent.
What causes Macular Degeneration?
Parts of the eye
No one knows exactly what causes dry macular degeneration. But research indicates it may be related to a combination of heredity and environmental factors, including smoking and diet.
The condition develops as the eye ages. Dry macular degeneration affects the macula — an area of the retina that’s responsible for clear vision in your direct line of sight. Over time tissue in your macula may thin and break down.
Factors that may increase your risk of macular degeneration include:
- Age. This disease is most common in people over 65.
- Family history and genetics. This disease has a hereditary component. Researchers have identified several genes that are related to developing the condition.
- Race. Macular degeneration is more common in whites than it is in other people.
- Smoking. Smoking cigarettes or being regularly exposed to smoke significantly increases your risk of macular degeneration.
- Obesity. Research indicates that being obese may increase your chance that early or intermediate macular degeneration will progress to the more severe form of the disease.
- Cardiovascular disease. If you have had diseases that affected your heart and blood vessels, you may be at higher risk of macular degeneration.
Vision with macular degeneration
Dry macular degeneration symptoms usually develop gradually and without pain. They may include:
- Visual distortions, such as straight lines seeming bent
- Reduced central vision in one or both eyes
- The need for brighter light when reading or doing close work
- Increased difficulty adapting to low light levels, such as when entering a dimly lit restaurant
- Increased blurriness of printed words
- Decreased intensity or brightness of colors
- Difficulty recognizing faces
Dry macular degeneration usually affects both eyes. If only one eye is affected, you may not notice any changes in your vision because your good eye may compensate for the weak eye. And the condition doesn’t affect side (peripheral) vision, so it rarely causes total blindness.
Dry macular degeneration is one of two types of age-related macular degeneration. It can progress to wet (neovascular) macular degeneration, which is characterized by blood vessels that grow under the retina and leak. The dry type is more common, but it usually progresses slowly (over years). The wet type is more likely to cause a relatively sudden change in vision resulting in serious vision loss.
Low-vision aids for macular degeneration
There are many devices specifically designed to help people with low vision function better. Different devices are available for different tasks. A trained professional can help you understand which device is best for accomplishing your particular needs. Training and practice are also important in order to become skilled at using any device.
Optical low-vision devices. Optical low-vision devices use lenses to magnify objects, making them easier to see. The lens strength will depend on your vision and the size of the object or print to be seen.
Magnifying spectacles. Which are stronger than ordinary glasses. They can be used for near tasks, such as reading, threading a needle, or any activity that requires detailed vision. The printed page or object must be held closer than usual in order to keep things in focus. One advantage of magnifying spectacles is that your hands remain free to hold reading materials or perform tasks.
Hand magnifiers. Familiar to most people and are available in varying strengths. Reading material is not necessarily held as close to the face as with magnifying spectacles, and some models come with a built-in light. High-quality and high-powered magnifiers are often available only in specialized stores or through vision rehabilitation professionals.
Stand magnifiers. Rest directly on the reading material, keeping the lens at the proper distance from the page. The ability to rest the magnifier on the page is useful for patients with a tremor or arthritis.
Telescopes. Used for seeing objects or reading signs that are far away. They can be handheld like a pair of regular binoculars or mounted on a pair of eyeglasses.
Video magnifiers. Electronic devices that use a camera and television screen to enlarge printed material, pictures, or small objects. They are adjustable and can enhance the material in different ways — for example, by making the print appear darker (increased contrast). The technology is developing rapidly, and electronic devices are becoming smaller, more portable and easier to use. Some can even be used for both distance and near tasks.
Other low-vision devices and techniques
There are numerous low vision aids, devices, and techniques to help make everyday activities easier, including:
- Electronic books, e-book readers and audio books
- Large-print books, newspapers, magazines, playing cards, and banking checks
- High-contrast and large number telephones, thermostats, watches, and remote controls; talking watches, timers, books, and medical devices
- Bold-tipped markers for easy-to-read shopping and phone number lists
- Computers that can magnify (on screen or on paper) any printed material or picture, or that read aloud what is viewed on screen
- Sitting closer to the television (this will not damage your eyes)
Lighting and glare
Good lighting and glare control are very important for people with low vision. A bright light should always be used when reading and its location should be adjusted for the greatest visibility without glare. Stronger light bulbs in darkly lit areas can make tasks like cooking, dressing, and walking up and down stairs easier. Wearing a hat with a wide brim or tinted wraparound sunglasses can shield your eyes from dazzling and annoying overhead lights or sunlight.
What is a Low Vision Specialist?
A Low Vision Rehabilitation Specialist is an optometrist or ophthalmologist who has been trained in Low Vision Rehabilitation. There are other professionals who specialize in specific aspects of low vision rehabilitation such as occupational therapists, orientation and mobility instructors. Low Vision Rehabilitation is available in most major medical centers and, in some cases, in private practices. Ask your retina specialist or eye doctor about referring you to a low vision specialist. See a Optometrist if you notice change in your central vision or your ability to see colors and fine detail becomes impaired. These changes may be the first indication of macular degeneration, particularly if you’re over age 50.