Basics of Macular Degeneration
by Bear Eye Care
Blog
Age-related macular degeneration, often called ARMD or AMD, is the leading cause of vision loss among Americans 65 and older.
AMD causes damage to the macula, which is the central portion of the retina responsible for sharp central vision. AMD doesn't lead to complete blindness because peripheral vision is still intact, but the loss of central vision can interfere with simple everyday activities such as reading and driving, and it can be very debilitating.
Types of Macular Degeneration
There are two types of macular degeneration: Dry AMD and Wet AMD.
Dry (non-exudative) macular degeneration constitutes approximately 85-90% of all cases of AMD. Dry AMD results from thinning of the macula or the deposition of yellow pigment known as drusen in the macula. There may be gradual loss of central vision with dry AMD, but it is usually not as severe as wet AMD vision loss. However, dry AMD can slowly progress to late-stage geographic atrophy, which can cause severe vision loss.
Wet (exudative) macular degeneration makes up the remaining 10-15% of cases. Exudative or neovascular refers to the growth of new blood vessels in the macula, where they are not normally present. The wet form usually leads to more serious vision loss than the dry form.
AMD Risk factors
- Age is the biggest risk factor. Risk increases with age.
- Smoking. Research shows that smoking increases your risk.
- Family history. People with a family history of AMD are at higher risk.
- Race. AMD is more common in Caucasians than other races, but it exists in every ethnicity.
- Gender. AMD is more common in women than men.
Detection of AMD
There are several tests that are used to detect AMD.
A dilated eye exam can detect AMD. Once the eyes are dilated, the macula can be viewed by the ophthalmologist or optometrist. The presence of drusen and pigmentary changes can then be detected.
An Amsler Grid test uses pattern of straight lines that resemble a checkerboard. It can be used to monitor changes in vision. The onset of AMD can cause the lines on the grid to disappear or appear wavy and distorted.
Fluorescein Angiogram is a test performed in the office. A fluorescent dye is injected into the arm and then a series of pictures are taken as the dye passes through the circulatory system in the back of the eye.
Optical coherence tomography (OCT) is a test based on ultrasound. It is a painless study where high-resolution pictures are taken of the retina.
Article contributed by Jane Pan M.D.
Recent Census Bureau data shows a population of approximately 70 million baby boomers (the generation born from 1946-1964). What does that have to do with low vision you may ask? Approximately 40 million people worldwide have some sort of blindness, and aging increases the incidence of macular degeneration and other vision impairment that qualifies them as “low vision” persons.
Low vision is a condition of the eye in which the vision falls below 20/70 in the better seeing eye. It impairs the recipients, rendering them unable to perform daily tasks that others take for granted. With this rising aging population, the awareness of low vision therapy, diagnosis, and treatments are more widely available.
Low vision treatment can help people recover from decreased visual function due to retinal disease, brain injury, neurological damage, and other causes.
It is not only the elderly population that is affected--approximately 20% of low vision patients are children under the age of 18. Childhood genetic disorders of the eye such as retinitis pigmentosa, albinism, Bests disease, ROP, rod/cone disorders, and glaucoma are among the causes of low vision in the pediatric population.
What can be done to help these millions?
There are eye care practitioners and therapists that specialize in low vision. They train patients to adjust their current lifestyles to make them more independent and utilize the current salvageable vision they do have. For example, if a person has lost their central vision due to macular degeneration, they can be trained to use their peripheral vision for many tasks.
Because patients with low vision cannot be functionally corrected with regular eye glasses, the use of telescopes, magnifiers, computer generated aids, training, biofeedback, and optical magnification devices are among some of the resources available to help. Occupational therapists also employ orientation and mobility assistance to help patients in their daily living skills.
There are many technologies that help to improve vision. One such technology is a bionic eye device that uses a pair of glasses with a camera that transmits video data to an implant in the back of that patients eye (the retina). This device uses technology similar to cochlear implants that stimulate auditory nerve signals to restore hearing. In the same way, visual impulses can be restored by stimulating neurons in the retina, brain, or optic nerve.
Maybe the Bionic Man TV series wasn’t too far out there and can someday be a reality............restoring vision to millions.
For more valuable information on low vision visit:
American Optometric Association AOA
American Occupational Therapy Association AOTA
American Academy of Ophthalmology AAO
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