Low Vision
Frequently Asked Questions
What is age-related macular degeneration?
How can macular disease affect eyesight?
How can abnormal blood vessels be detected?
What proven treatments are available for macular disease?
Are there any risks in laser treatment?
Can surgery help patients who have age-related macular degeneration?
Can stronger eyeglasses compensate for my vision loss?
How can I prevent further visual loss?
What hope does the future hold for macular disease patients?
How can I be alerted to changes in my vision?
Will my age-related macular degeneration affect my other eye?
Are my children likely to inherit age-related macular degeneration?
Can I prevent age-related macular degeneration by eating certain foods and taking vitamins?
Does macular disease mean I am more likely to have a stroke or heart attack?
Are any financial benefits or other services available for people who have lost vision?
What is considered "legal blindness"?
What is Low Vision?
People who have eye disease that is not correctable with standard refractive glasses, medical treatment or a surgical procedure, yet do have some remaining vision are term "low vision". The term encompasses the entire range of minimal refractive problems down to people who can just see motion. People with Low Vision have difficulty carrying out their daily activities or performing a job. They are unable to read their mail or see the television clearly. Walking or traveling may be difficult.
What is age-related macular degeneration?
In the United States, macular disease is the leading cause of permanent loss of central vision, affecting approximately 200,000 Americans each year. For some, the disease reduces the visual acuity below 20/200, which is considered legal blindness. This means that an individual is just able to see at 20 feet what a normal eye can see at 200 feet. Even though this loss seems dramatic, the macula only represents ten percent of the overall vision. The remaining eighty percent of vision, often called peripheral vision, is not affected and therefore no one becomes totally blind from macular degeneration. It is the re-application of this eighty percent vision that is the basis of Low Vision Rehabilitation.
How can macular disease affect eyesight?
There are two basic types of age-related macular degeneration (AMD): the dry type, which affects 90 percent of patients, and the wet type, which affects 10 percent. In the dry type, the macular tissue slowly begins to malfunction. The hallmark of this dry form of AMD is "drusen," which are yellow age spots in the macula. The reasons for this malfunction are not yet understood. The rate of visual loss is variable, with some people maintaining reading vision and good distance vision for years. Unfortunately, there is, as yet, no treatment.
In wet type AMD, blood vessels from the choroid grow through cracks in the barrier filter, which separates the retina and choroid. These abnormal vessels, which spread out under the macula, are referred to as a "choroidal neovascularization (CNV)," or a "net." AMD is the most common cause of CNV. Leakage or bleeding from these abnormal vessels is what causes visual loss.
Another frequent cause of subretinal neovascular membranes is severe myopia (nearsightedness); however, in many cases there is no known reason why the eye develops CNV.
How can abnormal blood vessels be detected?
In some patients, the eye doctor is able to see the presence of a subretinal neovascular membrane, or "net," during a routine examination, but in other patients it is necessary to obtain a fluorescein angiogram (FA) or indocyanine green angiogram (ICG). This test not only confirms the existence of abnormal blood vessel growth, but also determines the precise location of the vessels.
These tests are generally considered to be safe; side effects or serious reactions are not common. Patients with known sensitivities to the dyes or with iodine/shellfish allergies should avoid ICG dye.
What proven treatments are available for macular disease?
The Macular Photocoagulation Studies sponsored by the National Eye Institute have proven that a small percentage of patients have much less chance of significant visual loss if they are treated by laser photocoagulation than if they are not treated. It is estimated that 10 percent of patients with the wet type of age-related macular degeneration (AMD) may be candidates for laser treatment. The treatment can successfully eliminate the abnormal blood vessels in approximately 50 percent of these patients. Unfortunately, despite the best treatment, the abnormal vessels in some patients cannot be removed or recur with associated loss of vision.
Are there any risks in laser treatment?
In a small percentage of patients, laser photocoagulation may cause bleeding from the CNV being treated. Another complication may be accidental burning of the center of the macula, which can cause loss of central vision. However, these complications occur infrequently and rarely cause greater loss of central vision than would be expected in an untreated eye.
Can surgery help patients who have age-related macular degeneration (AMD)?
Surgery can do nothing for the "dry type" of AMD. However, in highly selected patients, surgical removal of the CNV or subretinal blood vessels, may provide improved vision. However, better results are obtained in younger patients.
Can stronger eyeglasses compensate for my vision loss?
Absolutely! For many years it was thought that stronger glasses would not help. Today, specialized optics in glasses can be used to shrink or minimize the area of vision loss and allow patients to use their peripheral vision. The glasses alone however are of little value. Only when combined in a program of rehabilitation and training can a patient enjoy an improvement in their quality of life thought the use of lo vision glasses.
How can I prevent further visual loss?
There are three basic ways that may prevent further vision loss in some cases and may be helpful to younger members of the family of a patient with macular degeneration:
- Limit your exposure to Ultra Violet light. Sunglasses, hats and visors are most helpful
- The Age Related Eye Disease study (AREDS) of the National Eye Institute showed that high levels of antioxidants and zinc significantly reduce the risk of advanced age-related macular degeneration (AMD) and its associated vision loss
- Recent studies have shown a positive correlation between good physical and cardiovascular fitness and improved vision in patients with macular degeneration. Recommendations for patients with macular degeneration include daily exercise, well managed blood pressure and management of high cholesterol, especially with the use of statin drugs when indicated
In addition to prevention of progression of the disease, the aggressive use of the eyes with low vision glasses helps maintain the connection between the brain and the visual system. This allows the correct interpretation of the damaged visual input by the brain and helps force the brain to compensate for the vision loss.
What hope does the future hold for macular disease patients?
Currently, researchers are trying to discover the reasons why age-related macular degeneration (AMD) develops. Some of this research is closely related to studies on the retina and the choroid as well as to studies on the aging process. Research is also under way to find out how and why new blood vessels grow, as well as how age, light and metabolism affect the macula's ability to function properly.
Many new research studies are enrolling patients with AMD, investigating nutritional supplements, laser for drusen, drugs to inhibit CNV, surgery to remove CNV or blood, or macular translocation surgery. Speak to your retina specialist to see if you may qualify. Ultimately, combination therapy will likely lead to the most effective palliative treatments for advanced AMD.
How can I be alerted to changes in my vision?
Macular disease causes no pain, redness, watering or tearing of the eye. The only way you can detect it is by frequently testing your central vision. You should cover each eye to test your ability to read with one eye only, and also for evidence of distortion or blurring of lines on a page. Your ophthalmologist can instruct you on how to test yourself at home. If you detect any changes in your eyesight, you should promptly return to your ophthalmologist.
Will my age-related macular degeneration (AMD) affect my other eye?
The risk that wet-type AMD will affect the other eye is about 10 percent per year. For this reason, Amsler Grid home tests and regular checkups are essential.
Are my children likely to inherit age-related macular degeneration(AMD)?
Approximately 20 percent of persons with AMD have had a parent with this condition. Therefore, there is a possibility that your children could develop signs of it later in life.
If I have age-related macular degeneration (AMD) and a cataract, will removing the cataract improve my vision?
That depends on the severity of the cataract and also on the severity of your macular disease. In a large study of patients with mild macular degeneration and cataracts, the patients that underwent cataract surgery had a significant increase in vision loss related to the progression of the macular degeneration as compared to those patients that had no surgery. It is postulated that the mild inflammation related to the cataract surgery causes a rapid decline of the sensitive macular cells leading to progression of the macular degeneration. The decision to proceed with cataract surgery should be made in consultation with your cataract surgeon, your retinal specialist and your Low Vision specialist.
Can I prevent age-related macular degeneration (AMD) by eating certain foods and taking vitamins?
The Age Related Eye Disease study (AREDS) of the National Eye Institute showed that high levels of antioxidants and zinc significantly reduce the risk of advanced age-related macular degeneration (AMD) and its associated vision loss.
Does macular disease mean I am more likely to have a stroke or heart attack?
Age-related macular degeneration (AMD) involves only the central portion of the retina. As far as we know, AMD has nothing to do with "hardening of the arteries", which can cause stroke or heart attack.
Are any financial benefits or other services available for people who have lost vision?
People who are legally blind may be eligible for a larger federal tax deduction and should contact their local IRS office.
People who are legally blind and 64 years of age or younger and unable to work may be eligible for Supplemental Security Income (SSI) or Social Security Disability. Persons who are experiencing problems related to low vision or blindness may be eligible to receive special transportation, reading and rehabilitation services. There are also support groups available.
What is considered "legal blindness"?
The ability to see, or "visual acuity" is found by using a system that compares distance vision between the patient and the standard set for normal vision. Separate measures are determined for each eye. The first value or numerator is the distance the testing distance, usually 20 feet. The second value or denominator is the size of the test letter. A "normal" person can see a 20 size letter at 20 feet. (20/20) If the letter size needs to be 10 times larger for you to see it, (10X20=200) your vision is 20/200.
Legal blindness is defined as 20/200 or less visual acuity in the better eye with best refractive glasses or a visual field of 20 degrees or less.