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Diabetic Eye Disease
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(click image for
larger view)
In diabetes, blood vessels in the
retina leak blood and protein. This
is seen by the ophthalmologist as
red hemorrhages and white-yellow
deposits within the retina. In advanced
cases, abnormal blood vessels (neovascularization)
grow on the optic nerve and the
retina.
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Diabetic eye damage starts with injury
to blood vessels within the retina from elevated blood sugar.
Blood vessels become leaky with blood and protein leaking
out into the retina, and threatening vision. If you have
diabetes, your body does not use and store sugar properly.
High blood sugar levels create changes in the veins, arteries
and capillaries that carry blood throughout the body. This
includes the tiny blood vessels in the retina, the light-sensitive
nerve layer that lines the back of the eye. For this reason,
careful control and monitoring of one's blood sugar is an
important step towards prevention of diabetic eye disease.
There are two types of diabetic eye disease:
background diabetic retinopathy (BDR) and proliferative
diabetic retinopathy (PDR). In BDR, there are small retinal
hemorrhages, protein leakage, and retinal infarction. In
general, vision remains good in BDR. Sometimes vision is
reduced in BDR from swelling of the retinal tissue. This is called clinically significant macular
edema. BDR is a precursor to PDR, a more serious form of
diabetic retinopathy.
In eyes showing proliferative diabetic
retinopathy (PDR), the retinal blood vessels are so damaged
that they become occluded. In response, the retina grows
new blood vessels. Unfortunately, these new blood vessels
are abnormal and fragile. They grow above the surface of
the retina rather than in the retina, so they do not resupply
the retina with the blood and oxygen it requires for normal
functioning.
These new blood vessels can bleed and cause
a vitreous hemorrhage. Blood in the vitreous, the clear
gel-like substance that fills the inside of the eye, blocks
light rays from reaching the retina. A small amount of blood
will cause dark floaters, while a large hemorrhage might
diminish all vision, leaving only light perception.
The new blood vessels also cause scar tissue
to grow. The scar tissue shrinks, wrinkles and pulls on
the retina and causes distorted vision. If the pulling is
extreme, the retina detaches from the eye wall and causes
vision loss.
Laser surgery may be used to seal leaking
blood vessels and reduce the risk of bleeding. The eye will
eventually absorb blood from a vitreous hemorrhage, but
this can take days or months or years. If the vitreous hemorrhage
does not clear within a reasonable time, or if a retinal
detachment is detected, an operation called a vitrectomy
can be performed to remove the hemorrhage and the abnormal
blood vessels that caused the bleeding.
People with PDR sometimes have no symptoms
until it is too late to treat them. The retina may be badly
injured before there is any change in vision. There is considerable
evidence to suggest that rigorous control of blood sugar
decreases the chance of developing serious PDR. Because
diabetic retinopathy may initially have no symptoms, patients
with diabetes you should have their eyes examined regularly
by an ophthalmologist. The timing of these eye examinations
as recommended by the American Academy of Ophthalmology
is:
When type 1 diabetes is diagnosed between ages 10 and 30 years, significant retinopathy may become apparent after 6 to 7 years of disease. Ophthalmic examinations beginning 5 years after the diagnosis of type 1 diabetes are therefore recommended. The time of onset of type 2 diabetes is often difficult to determine and may precede the diagnosis for a number of years. For that reason, any patient over the age of 30 years should be referred for ophthalmologic examination at the time of diagnosis. Finally, patients with diabetes who become pregnant experience a higher risk of developing diabetic retinopathy because the pregnancy causes changes in metabolic control. Diabetic patients who are planning to become pregnant are encouraged to have their eyes examined prior to conception, to be counseled on the risk of development and/or progression of diabetic retinopathy, and to make every attempt to lower their blood glucose levels to as near normal as possible for their own health and the health of the fetus. During the first trimester, another eye examination should be performed;
subsequent follow-up will depend on the level of retinopathy found. The above recommendations do not apply to women who develop gestational diabetes, because such individuals are not at increased risk for diabetic retinopathy during pregnancy.
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