Macular Degeneration
Michael Pinnolis, M.D., Chief of Visual Services, discusses Macular Degeneration
The term macula refers to the anatomical center of the retina.
The macula is the focal point for the lens system of the eye. It is
similar to film in a camera. An image is projected onto the macula and
is then changed into nerve 
signals
and sent to the brain for interpretation. The macula is the part of
the retina that is used for most visual functions. You read with the
macula, see straight ahead with the macula and perceive colors with
the macula. The retina outside of the macula is used only for peripheral
or side vision and for seeing in the dark. Any damage to the macula
may have a profound effect on one’s vision.
Age-related Macular Degeneration (ARM, AMD) causes slow deterioration of the visual cells, photoreceptors in the macula. No one yet knows what causes this process of cell degeneration, but it occurs more frequently as one gets older. It is estimated that about 10% of patients over 65 years of age have some degree of macular degeneration. The amount of visual impairment is variable and the progress of disease is unpredictable. Not everyone will experience visual problems from macular degeneration.
Cause
The cause or causes of macular degeneration is unknown. Research strongly suggests that there are multiple causes or risk factors for macular degeneration, and that patient must have more than one of these risks to develop the disease: these factors include aging, genetics, circulation, nutrition, environment and anatomy.
There is definitely a hereditary pattern in some families, although we often see ARMD in some patients with absolutely no family history. Some scientists feel that poor blood supply or poor circulation to the macula may play a role in this disease. This is supported by the finding that people who smoke have a higher risk of developing significant macular degeneration. The strongest association so far seems to be a lack of certain nutritional factors. In particular, research has focused on a certain class of vitamins and minerals known as anti-oxidants (e.g. Vitamin E, beta-carotene, Selenium, Vitamin C) and on the mineral zinc. These vitamins tend to be found in green vegetables. Research has shown that patients who have a diet rich in green, leafy vegetables or who have higher blood levels of these vitamins, tend to have less severe macular degeneration. Other research has suggested the benefit of certain nutrition supplements such as lutein, zeaxanthine, and omega 3 fatty acids. Recently, a major prospective, controlled study demonstrated that these vitamins given in very high doses can prevent the progression of macular degeneration.) Others feel that ultraviolet light (sunlight) exposure may play some role in damaging the retina. Finally, some doctors feel the wall of the eye may become too rigid in later life, leading to this problem. Much more work remains to be done.
Symptoms
In early macular degeneration, patients may not experience any symptoms.
As time progresses they may find that their central vision becomes
blurry and that this blurriness is not correctable with new glasses.
If the cell destruction in the macula becomes severe, the blurring
effect can be substantial. Reading and driving may become very difficult.
Because this affects only the center of the retina, patients will
find that their peripheral vision remains intact. Macular degeneration
almost NEVER totally blinds a patient. Nevertheless, the effect on
one’s lifestyle can be very troubling. Sometimes, patients will
also notice that their vision is becoming distorted: straight lines
may become curved
or get a "bump" in them. This effect may be most noticed
on a grid pattern, such as tiles or windowpanes. You eye doctor may
provide you with a small paper chart that has crossed lines printed
on it called an Amsler Grid. This grid
can be used at home so that you may test yourself to find early, subtle
changes in your vision. If you notice any sudden change in your vision,
especially distortion, you should contact your eye doctor immediately.
To download an Amsler Grid go to Prevent Blindness America's Age-Related
Macular Degeneration Test.
Examination and Testing
In order to diagnose macular degeneration, your eye doctor will need to perform a dilated examination of the retina. Sometimes it is an easy matter to determine the extent of macular degeneration by simply looking at the retina. However, many times further testing is required. The most common test is a series of special photographs called a fluorescein angiogram. In this test a dye, sodium fluorescein, is injected into a vein in the arm. It circulates rapidly through the blood stream and in a few seconds flows into the blood vessels of the eye. The dye can be seen on photographs if special filters are used in the camera. No radiation is involved in this test. If there are abnormal blood vessels present, the dye will leak from those vessels and be easily visible on the photographs. By this means, your doctor can determine whether abnormal blood vessels are present and whether they are in a location suitable for safe laser treatment. Other testing may include angiography with another dye, indocyanine gree (ICG) or a scanning cross section of the retina done with laser, called OCT.
Dr. Michael Pinnolis is a Retina Specialist and practices in the Retina Service in Kenmore Visual Services of Harvard Vanguard Medical Associates.
Find out more about
Age-Related Macular Degeneration:
- Progression
- Treatment
- Prevention
- Examination and Testing
- Low Vision Examinations and Devices