Macular
degeneration is the most common cause of visual
loss in the U.S. in patients over 55 years of age.
Although it rarely causes total blindness, it may
produce serious loss of central vision.
This page will provide a basic understanding of
what causes macular degeneration, how it affects
eyesight, and what treatment is available.
What is the macula?
The retina is the nerve tissue that lines the back wall of the eye. Much like
the film in a camera, the retina is sensitive to light. It transforms light
energy to nerve stimuli, and “sends a picture” through the optic
nerve to the brain. The macula is a specialized are in the central part of
the retina. Because of the abundance of nerve connections that serve the
macula, it is the part of the retina that provides for sharp, clear color
vision. Our ability to read and to see fine detail depends upon the health
of the macula.
Unfortunately, the macula is prone to degenerative
changes that affect the rest of the retina less
frequently. There are unusual types of macular
degeneration that start early in life. However,
most patients begin to notice visual symptoms after
age 50.
What are some symptoms of macular disease?
An object that normally appears straight, such as a telephone pole, may seem
bent or crooked. A dark gray spot may appear in central vision. The size
of an object may appear different to each eye. Colors may not look the same
to each eye. Any of these changes should be reported to your physician and
followed up with a thorough retinal exam.
What changes are seen in the eye?
The earliest sign of macular degeneration is the formation of yellow deposits
under the retina. These deposits, called drusen, may cause the overlying
retina to become slightly distorted. This may result in mild distortion of
vision. However, drusen do not produce any severe loss of vision. This type
of macular degeneration is referred to as the “dry” type and
requires no treatment. It may cause a slowly progressive loss of vision,
but visual loss is usually mild. Eyesight may be helped somewhat with the
use of special low vision lenses, magnifying lenses for close-up and telescopic
lenses for distance. Your physician will refer you to an expert in this field
if he feels these aids would be beneficial to you. Approximately 7% of patients
with drusen progress to the more serious form of macular degeneration, often
referred to as the “wet” type. In this stage, abnormal blood
vessels grow under the retina. These vessels, called subretinal neovascularization,
are thin-walled and fragile and tend to leak fluid and blood into the retina.
Untreated, this leakage causes scar tissue to develop which, in turn, results
in loss of central vision. Macular degeneration does not cause complete blindness
since peripheral (side) vision is not affected. It does, however, impair
the ability to read. Early detection of abnormal blood vessels increases
the chance of saving central vision.
DIAGNOSIS
In patients with macular degeneration, it is important to determine if any
abnormal blood vessels are present and if so, their location. Two photographic
tests can be used to detect these vessels and determine appropriate treatment:
Fluorescein and Indocyanine Green Angiography. With both tests, a dye is injected
into a vein in the arm. The dye quickly passes through the circulation to the
eye and serial photographs reveal any leaking blood vessels. These tests do
not involve X-rays and are quite safe. The doctor may recommend either or both
tests. Rarely, patients may become nauseated or have allergic reactions to
the dye. Patients with a known Iodine (i.e. shellfish) allergy should report
this to the physician before ICG testing. These patients will be premedicated
to eliminate the risk of a severe allergic reaction.
TREATMENT
If abnormal blood vessels are present, progressive visual loss occurs in approximately
2/3 of patients. Various types of lasers can be used to treat the abnormal
blood vessels and reduce the severity of the visual loss.
Standard laser treatment is an
intense beam of light which seals the abnormal
blood vessels. The body can then reabsorb the fluid
and blood that has accumulated. This type of laser
will cause a scar and leave a permanent blind spot.
As such, it is not used, if abnormal vessels are
beneath the center of the retina.
Photodynamic therapy or PDT involves
injecting a photosensitive dye into an arm vein
and a low dose laser to activate the dye within
the abnormal retinal blood vessels. The activated
dye causes closure of the abnormal blood vessels.
Most patients require repeated treatments at three
month intervals with the average patient requiring
4 to 5 sessions. In some cases, injection of an
anti-inflammatory medicine (intravitreal
Kenalog) may be used to augment the laser
treatment.
Transpupillary thermotherapy or TTT is
a 3rd type of laser which slowly heats the abnormal
blood vessels to reduce their tendency to bleed.
Unlike standard laser treatment, the lower dose
TTT laser delivers heat to the area of abnormal
blood vessels without causing a permanent blind
spot.
The type of laser used will be determined by the
type, size and location of the abnormal blood vessels.
Some patients may require more than one treatment.
The goal of treatment is to stabilize vision. Your
physician will discuss the various options with
you and suggest the most appropriate treatment
for your situation.
There are three experimental medicines presently
being evaluated for the treatment of abnormal vessels
in patients with ARMD. Two of these medicines,
Macugen and RhuFab are injected into the eye while
the third is injected behind the eye. The medicines
have not been approved by the FDA at this time
pending review of additional data.
After treatment, repeated exams and angiographies
are essential to monitor the macula for recurrent
vessels. If leaking vessels recur, there will be
distortion of central vision such that straight
lines look curved or wavy.
One good way for patients to monitor their own
vision is with an Amlser
grid. This will be given to you to use regularly
at home. At the first sign of a change in the pattern
of the Amsler grid, you should contact the office
immediately for an appointment.
Important facts to know before laser treatment
Treatment will not bring back perfect vision.
Treatment may produce a small blind spot (scotoma), depending on the type of
laser used.
If successful, treatment will prevent further deterioration in central visual
acuity. In some cases, significant improvement can occur.
Repeated office visits and Fluorescein and/or ICT angiography will be needed
following treatment.
Careful monitoring is important to detect any recurrence of the abnormal blood
vessel growth.
Low vision lenses are often helpful.
PREVENTION
Smoking and Macular Degeneration
A large study has shown that the risk for developing late age-related macular
changes for current smokers was 2.5 times the risk for persons who reported
having never smoked. Also, current smokers were more likely to start developing
early macular changes in their 50s and 60s than at older ages, with >50%
having a higher risk for developing retinal pigmentary changes. These findings
further support the view that smoking is a major risk factor for progression
of AMD (Age-related Macular Degeneration). Furthermore, a decrease in risk
can be seen following cessation of smoking.
Diet:
A large study has shown that vitamins C, E, A and Zinc are helpful in reducing
the risk of developing abnormal blood vessels in patients with Age-related
Macular Degeneration. The recommended doses are listed below. A diet high
in Lutein and Zeaxanthin has also been shown to reduce the risk of vision
loss in patients with Age-related Macular Degeneration.
Lutein-zeanxathin content of fruits and
vegetables (micrograms/100G)
Kale 21,900
Collard greens 16,300
Spinach (cooked) 12,600
Spinach (raw) 10,200
Parsley (not dried) 10,200
Mustard greens 9,900
Dill (not dried) 6,700
Celery 3,600
Scallions (raw) 2,100
Leeks (raw) 1,900
Broccoli (raw) 1,900
Broccoli (cooked) 1,800
Leaf lettuce 1,800
Green peas 1,700
Pumpkin 1,500
Brussels sprouts 1,300
Summer squash 1,200
Corn (yellow) 790
Yellow pepper (raw) 770
Green beans 740
Green pepper 700
Cucumber pickle 510
Green olives 510
Dietary supplementation for patients with macular
degeneration
Vitamin C 500mg.
Vitamin E 400iu.
Betacarotene 15mg
Zinc 80mg
Copper 2mg.
Finally, there is some evidence that sun exposure
may exacurbate Age-related Macular Degeneration.
Sunglasses should be worn when outdoors. |
