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Diabetes damages the body’s normal circulation which
is why people with diabetes may have problems with
circulation to their legs, kidneys, heart, brain, and eyes.
At least 50 percent of all diabetics will develop diabetic
retinopathy (abnormal retinal blood circulation), and the
incidence increases with the duration of the disease.
After 20 years, more than 90 percent of diabetics have
some degree of diabetic change.
Diabetic retinopathy is a leading cause of blindness in
the United States in middle-aged adults. Fortunately, new
methods of treatment in recent years have decreased
blindness among diabetics and have increased the
possibility of retaining useful vision.
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There are two main types of diabetic retinopathy:
non-proliferative and proliferative. In non-proliferative
diabetic retinopathy, there is leakage caused by damage
to small retinal blood vessels (capillaries). This leakage
allows proteins and lipids from the blood to accumulate
in the retina, causing swelling. If this swelling occurs in
the area of central vision (macular edema), sight may
be significantly diminished. As the disease progresses,
retinal capillaries may also become closed off, resulting
in poor retinal nutrition. Lack of circulation to the center
of vision (macular ischemia) can result in severe and
permanent loss of central vision.
When there is widespread impairment of retinal nutrition
due to capillary leakage and closure, proliferative diabetic
retinopathy develops. The poorly nourished retina sends
out a chemical “distress signal” which causes new blood
vessels to grow (proliferate) on the retinal surface.
Unfortunately, these new blood vessels are very fragile
and often rupture, allowing bleeding to occur within the
eye (vitreous hemorrhage). Scar tissue can also grow
around the abnormal blood vessels which may lead to
retinal detachment and possible permanent blindness.
The proliferative form of diabetic retinopathy is present
in approximately 20 percent of patients with diabetes of
ten years duration.
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In the early stages of diabetic retinopathy, there are
usually no symptoms. Therefore, it is very important that
all patients with diabetes have a comprehensive dilated
eye examination at least once a year before any symptoms
develop. During this exam, your eye specialist can check
for any signs of damage to the retina and optic nerve,
including leaking blood vessels, swelling of the macula,
and growth of new vessels. To help prevent the
development and progression of diabetic retinopathy,
patients are urged to control their blood sugar, blood
pressure, and cholesterol levels.
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Treatment is aimed at the main causes of decreased vision.
Macular Edema
Macular edema is caused by damage to retinal capillaries which leads to leakage of blood products into the retina.
- Large clinical trials have shown that the application of focal laser to areas of retinal swelling can stabilize the vision and reduce the risk of vision loss by 50 percent.
- The injection of steroids, such as triamcinolone, either around or into the eye has also recently been found to be of benefit. Side effects of steroid injections include increased eye pressure and cataract formation.
- A new class of medications target the “distress signal” sent out by a poorly nourished retina. These agents bind and block the action of vascular endothelial growth factor (VEGF) and can be directly injected into the eye. Adverse effects of injections of these agents into the eye are rare but include bleeding, infection, cataract, and retinal tear or detachment.
Patients may need multiple procedures or a combination of treatments to control the leaking fluid.
Proliferative Diabetic Retinopathy
Widespread impairment of retinal blood circulation leads to the development of new, fragile blood vessels.
Large clinical trials have shown that a procedure called scatter laser photocoagulation can be effective in halting or reversing new vessel growth. Many eyes, even without visual problems, need to begin laser treatments if there are certain abnormal vessels present. Those eyes, having no visual problems, must be detected by examination. Overall, the incidence of blindness over two years can be reduced by 66 percent for eyes with new vessels on the optic nerve and by 37 percent for eyes with new vessels in other locations. The laser treatment consists of applying multiple laser burns to the peripheral retina, often divided into several sessions. Although mildly uncomfortable, the treatment usually can be done without the need for local anesthesia. The main complications from treatment are loss of some peripheral vision, a decrease in night vision, occasionally some loss of central vision, and possible mild enlargement of the pupil. If laser treatment is needed, the risk factors of not being treated are much higher than the risk of being treated.
Again, a new class of medications targeting VEGF produced by poorly nourished retina can be directly injected into the eye. The anti-VEGF drugs Avastin and Lucentis have been used with good results in managing proliferative diabetic retinopathy, often along with scatter laser photocoagulation treatment.
Vitreous Hemorrhage and Tractional Retinal Detachment
In cases where laser treatment is not successful in preventing hemorrhage into the eye or when a retinal detachment from scar tissue has occurred, a type of surgery called vitrectomy is often helpful. In the operating room, a microsurgical instrument is inserted into the eye, and the blood-stained vitreous is removed and replaced by a clear sterile solution. Fibrous bands which may cause retinal detachment are removed to allow the retina to flatten and return to a more normal configuration. Vitrectomy remains an operation performed only on eyes in which no other treatment is useful. Approximately 60 percent to 70 percent of selected eyes, otherwise hopelessly damaged, can be restored to at least ambulatory vision. Some eyes, however, actually can return to very good vision.
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It is critical for all diabetics to have a comprehensive eye
exam at least once a year to evaluate for the presence of
retinopathy. Patients should remember that both macular
edema and proliferative retinopathy can develop without
symptoms. Patients with visual symptoms and/or visual
loss, at any stage of the disease, should be evaluated
without delay to find out the cause of the visual change.
Early detection and timely treatment can prevent vision
loss.
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The overall maintenance of health is important in avoiding
circulation damage to the brain, heart, kidneys, and eyes.
Although perfect solutions are not available for the
prevention of visual loss, the outlook for maintenance of
useful vision is favorable. Early detection and appropriate
therapy can be sight-saving. All diabetics should work to
lower their vascular risk factors. Important advice includes:
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Eat healthy.
- Exercise.
- Avoid smoking.
- Control your blood pressure and blood sugar.
- Lower your cholesterol levels.
- Carefully follow your medical doctor’s instructions.
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