Macular Degeneration
Introduction
Macular degeneration is a common eye disorder and the leading cause of loss of reading vision in the United States. It is a condition in which damage occurs to the retina, usually from an aging change. While total blindness never occurs from this condition, the ability to read and do close work can be severely affected.
What is macular degeneration?
Macular degeneration is the medical name given to a group of conditions that all have the same result, blurred or distorted central vision.
The retina is a thin layer of nerve tissue that lines the back of the eye. It receives light signals coming in from the front of the eye and sends them on to the brain so that vision can occur.
The macula is that portion of the retina we use for central vision such as reading or driving a car.
Beneath the retina there are blood vessels and pigment cells that nourish and maintain the retina in good working condition. With aging, the retina, pigment cells, and blood vessels beneath the macula may show signs of degeneration, hence the term macular degeneration.
One of the earliest changes that can be seen is the change in pigment cells caused by drusen. Drusen are yellow/white deposits beneath the retina that represent a buildup of waste products. Drusen are an aging change and are seen in just about everyone older than 60. If the drusen are located in the center vision area of the macula or if there is widespread loss of the pigment cells there can be a mild or moderate loss of central vision for which there is no treatment other than a good reading light and magnifying glasses. This is called dry or atrophic macular degeneration. About 90% of all age related macular degeneration is of this type. The rest of the retina, outside the macula, remains unaffected and so peripheral or side vision is not lost. Low vision aids may enable patients with chronic dry macular degeneration to live with only a partial change in their lifestyle. Some doctors believe that nutritional supplements (eye vitamins) may slow macular degeneration, although this has not yet been proven.
The retina is a thin layer of nerve tissue that lines the back of the eye. It receives light signals coming in from the front of the eye and sends them on to the brain so that vision can occur.
The macula is that portion of the retina we use for central vision such as reading or driving a car.
Beneath the retina there are blood vessels and pigment cells that nourish and maintain the retina in good working condition. With aging, the retina, pigment cells, and blood vessels beneath the macula may show signs of degeneration, hence the term macular degeneration.
One of the earliest changes that can be seen is the change in pigment cells caused by drusen. Drusen are yellow/white deposits beneath the retina that represent a buildup of waste products. Drusen are an aging change and are seen in just about everyone older than 60. If the drusen are located in the center vision area of the macula or if there is widespread loss of the pigment cells there can be a mild or moderate loss of central vision for which there is no treatment other than a good reading light and magnifying glasses. This is called dry or atrophic macular degeneration. About 90% of all age related macular degeneration is of this type. The rest of the retina, outside the macula, remains unaffected and so peripheral or side vision is not lost. Low vision aids may enable patients with chronic dry macular degeneration to live with only a partial change in their lifestyle. Some doctors believe that nutritional supplements (eye vitamins) may slow macular degeneration, although this has not yet been proven.
Wet macular degeneration: A potentially treatable problem
About 10% of older patients with drusen and pigment degeneration may develop abnormal new blood vessels under the macula. The blood vessels may leak or hemorrhage causing a marked decrease in the reading vision. It is for this second group of patients that laser treatment can sometimes be useful. The laser beam is aimed at the abnormal blood vessels beneath the retina, cauterizing them and preventing any further leakage or spread into the macula.
Diagnosis
The major symptom of macular degeneration is blurred vision. Oftentimes patients will notice distortion and/or blank spots when they try to read. A useful test to check for macular degeneration is the Amsler grid. Following are two examples of changes in the Amsler grid in a patient with macular degeneration.
Sometimes when macular degeneration has begun outside the very center vision area, the patient will not have symptoms but a careful examination by an eye doctor viewing the macula with an opthalmoscope may point to a potential problem.
Sometimes when macular degeneration has begun outside the very center vision area, the patient will not have symptoms but a careful examination by an eye doctor viewing the macula with an opthalmoscope may point to a potential problem.
Fluorescein angiography
Fluorescein angiography is perhaps the best and sometimes the only way to make the diagnosis of macular degeneration and to determine which eyes can be treated with laser. In this test a vegetable dye is injected into a vein in the patient's hand or arm. The dye is carried by the blood stream to the retina and a rapid sequence of pictures are taken. If there are abnormal leaky blood vessels under the retina, they will show up on the special pictures. In this way the exact location and extent of the abnormal blood vessels can be determined. This test is not painful and no x-rays are used. (After the angiogram patients may notice some temporary yellow discoloration of the skin and urine but this lasts only a short time.)
Laser treatment for macular degeneration
The laser is a bright light that can be focused to a very small spot on the retina. When this highly focused beam hits the retina, the tissue heats up and leaking blood vessels are cauterized or coagulated. The treatment can be performed in the office or in the outpatient department of the hospital. The laser treatment itself is not painful. The patient is given drops to dilate the pupils and then either a topical
anesthetic or a local injection behind the eyelid is used to numb the eye. After treatment the eye will be protected for several hours but normal activities can usually be resumed the very next day. Two to three weeks later patients are asked to return for a repeat fluorescein angiogram to determine the effectiveness of treatment and to decide whether more laser is needed. Even after successful laser treatment new blood vessels can recur. Therefore periodic examinations are necessary. Further, if the blood vessels grow into the very center vision area, laser treatment may not be as beneficial. When this occurs a scar eventually develops under the retina in this area leading to permanent loss of reading vision.
Will the other eye become affected?
Macular degeneration is generally a problem of aging so both eyes usually show some changes. Patients who develop leaking blood vessels under the retina in one eye have a 5-10% chance per year of this occurring in the other eye as well. It is for this reason that it is very important for patients to check their center vision on a regular basis using an Amsler grid and report any new blurring or distortion as soon as possible. In that way leaking blood vessels may be identified when they are still in a treatable location. Unfortunately, at the present time, there is no treatment that will prevent new blood vessels from developing.
How will macular degeneration change my life?
Macular degeneration can cause mild to severe loss of central vision which can lead to significant changes in lifestyle. Reading and other close work may no longer be possible. Patients may find their vision affected to such an extent that they can no longer safely drive a car. Some patients in occupations requiring good sharp central vision may have to find other types or work.
Most people have only mild changes and even those with more advanced macular degeneration never lose their side vision, so total blindness does not occur. With the aid of special magnifiers and glasses even patients who are legally blind can learn to use their side vision to do necessary reading and writing. Such activities as housekeeping and cooking are almost always possible even for those patients who have lost the center vision in both eyes.
Most people have only mild changes and even those with more advanced macular degeneration never lose their side vision, so total blindness does not occur. With the aid of special magnifiers and glasses even patients who are legally blind can learn to use their side vision to do necessary reading and writing. Such activities as housekeeping and cooking are almost always possible even for those patients who have lost the center vision in both eyes.
Using the Amsler Grid
Proper use of the grid will enable you to detect changes in your center vision which can occur when there is just a small amount of fluid under your retina.
To perform the test properly:
1.Wear the glasses you normally wear for reading.
2.Hold the grid at your normal reading distance.
3.Cover one eye and with the other eye, look at the center dot.
While you are looking at the center dot, you should be able to see the four corners of the large square. You should also be able to see that the large square is composed of many smaller squares.
2.Hold the grid at your normal reading distance.
3.Cover one eye and with the other eye, look at the center dot.
While you are looking at the center dot, you should be able to see the four corners of the large square. You should also be able to see that the large square is composed of many smaller squares.