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Diabetes mellitus is a condition which impairs the body's ability to
use and store sugar. Elevated blood-sugar levels, excessive thirst and
urination, and changes in the body's blood vessels are all characteristic
of the disease. Diabetes may affect vision by causing cataracts, glaucoma
and, most importantly, damage to blood vessels inside the eye.
What is Diabetic Retinopathy?
Diabetic retinopathy, a complication of diabetes, is caused by changes
in the blood vessels of the retina, the light-sensing nerve layer in the
rear of the eye. These damaged blood vessels may leak fluid or blood,
and develop fragile brush-like branches and scar tissue. The images which
the retina sends to the brain become blurred, distorted or partially blocked.
The risk of developing diabetic retinopathy increases the longer a person
has diabetes. About 80% of the people with at least a 15-year history
of diabetes have some blood vessel damage to their retina.
Diabetic retinopathy is particularly likely to occur at a younger age in juvenile
diabetics, who have been diagnosed with the condition during their childhood
or teenage years. Diabetic retinopathy is the leading cause of new blindness
among adults in the United States, and people with untreated diabetes
are said to be 25 times more prone to blindness than the general population.
However, with improved methods of diagnosis and treatment only a small
percentage of those who develop retinopathy experience serious problems
with vision.
Types of Diabetic Retinopathy
Background retinopathy is an early stage of diabetic retinopathy. In
this stage, fine blood vessels within the retina become narrowed or obstructed
while others enlarge to form balloon-like sacs. These altered vessels
leak blood and fluid, causing the retina to swell or form deposits called
exudates. Sight is usually not seriously affected. It can, however, lead
to more advanced sight-threatening stages, and for this reason is considered
a warning sign.
In some cases, the leaking fluid collects in the macula, the portion of the retina responsible for
detailed vision, such as reading. This problem is called macular edema. Reading
and close work may become more difficult because of this condition.
Proliferative retinopathy describes the changes that occur when
new, abnormal blood vessels begin growing on the surface of the retina
or the optic nerve. These new blood vessels, called neovascularization,
have weaker walls and may rupture and bleed into the vitreous, the clear
gel-like substance that fills the center of the eye. This leaking blood
can cloud the vitreous and partially block the light passing through the
pupil towards the retina, causing blurred and distorted images. These
abnormal blood vessels frequently grow scar tissue with them which may
pull the retina away from its normal position at the back of the eye (detached
retina). Abnormal blood vessels may also grow around the pupil (on
the iris) causing glaucoma by increasing pressure within the eye.
Proliferative diabetic retinopathy is the most serious form of diabetic
retinal disease. It affects up to 20% of diabetics and can cause severe
loss of sight, including blindness.
Cause and Symptoms
The cause of diabetic retinopathy is not completely understood; however, it is known that diabetes
damages small blood vessels in various areas of the body. Pregnancy and high blood pressure
may aggravate diabetic retinopathy.
Although gradual blurring of vision may occur if macular edema is present,
sight is usually unaffected by background diabetic retinopathy and changes
in the eye can go unnoticed unless detected by a medical eye examination.
When bleeding occurs in proliferative retinopathy, the sight may become
hazy, spotty or even disappear altogether. While there is no pain, this
severe form of diabetic retinopathy requires immediate medical attention.
Detection and Diagnosis
A comprehensive medical eye examination and appropriate treatment by Dr. Lockhart
is the best protection against eye damage
due to diabetic retinopathy. Serious retinopathy can be present without
symptoms and improve with treatment. Therefore, people with diabetes should
be aware of the risks of developing visual problems and should have their
eyes examined regularly. (Periodic eye examinations are also advisable for
apparently healthy people, because such examinations help detect the presence
of diabetes and other diseases.)
To detect diabetic retinopathy, the Gailey Eye Clinic physicians
conduct a painless examination of the inner part of the eye using an instrument
called an ophthalmoscope. The pupils may need to be dilated with eye drops.
If diabetic retinopathy is noted, the Gailey Eye Clinic physicians may obtain
color photographs of the retina. Sometimes a specialized technique is
used which provides great detail about retinal blood vessels and leakage.
First, a fluorescent dye is injected into a vein in the arm. The dye travels
through the bloodstream, including the blood vessels of the retina. Photographs
are taken in rapid succession as the dye passes through the retinal blood
vessels. This technique, called Fluorescein angiography, is often
used by the Gailey Eye Clinic physicians to determine if further treatment
is necessary.
Treatment
When diabetic retinopathy is diagnosed, the Gailey Eye Clinic physicians
consider the patient's age, history, lifestyle, and the degree of damage
to the retina before deciding whether treatment or further observation
of the disease is most appropriate. In many cases treatment is not necessary;
in others it is recommended to halt the damage of diabetic retinopathy
and improve sight wherever possible.
Laser Surgery
The most significant treatment is ophthalmic laser surgery, which seals or
photocoagulates the leaking blood vessels. During this procedure, a powerful
beam of laser light is focused on the damaged retina. Small bursts of
the laser's beam seal leaking retinal vessels to reduce macular edema.
When larger applications of the laser beam are scattered throughout more
peripheral areas of the retina, the small laser scars reduce abnormal
blood vessel growth (neovascularization) and help bond the retina to the
back of the eye. Laser surgery does not require an incision and may be performed by the Gailey
Eye Clinic physicians on an outpatient basis. If diabetic retinopathy
is detected early, photocoagulation by laser surgery retards vision loss.
Even in the more advanced stages of the disease (proliferative retinopathy),
it reduces the chance of severe visual impairment.
Other Treatments
If the vitreous is clouded by hemorrhage, laser photocoagulation cannot be used until the
blood settles or clears. In some cases of persistent vitreous hemorrhage, cryotherapy
of the retina, using local anesthesia and a cold instrument probe, may help shrink the abnormal
blood vessels.
In advanced proliferative diabetic retinopathy, the Gailey Eye Clinic
physicians may recommend a vitrectomy. This is a microsurgical procedure,
performed in the operating room, to remove the blood-filled vitreous and
replace it with a clear solution. About 70% of vitrectomy patients notice
an improvement in sight after surgery.
The Gailey Eye Clinic general physicians may recommend a vitrectomy soon
after the vitreous becomes clouded by blood, or may wait from several months
up to a year to see if the blood clears on its own. Determining the most
appropriate time to perform surgery depends on the extent of damage, as
well as the condition of the other eye. If proliferative diabetic scar tissue
detaches the retina from the back of the eye, severe sight loss or blindness
can result unless surgery is performed to reattach the retina.
Successful treatment of diabetic retinopathy depends not only on early detection
through medical eye examinations and treatment, but also on the patient's
attitude and attention to medications and diet. Physical activity presents
few problems to people with background retinopathy. Occasionally, some
restriction in activity for patients with active proliferative retinopathy
is recommended.
Vision Loss is Largely Preventable
Early detection of diabetic retinopathy is the best protection against loss
of vision. It is important to remember that diabetic retinopathy may be
present without any symptoms. People with diabetes should schedule examinations
by an ophthalmologist at least once a year. More frequent medical eye
examinations may be necessary once diabetic retinopathy has been diagnosed.
In most cases, with careful monitoring, The Gailey Eye Clinic general
physicians can begin treatment before sight is affected. Modern ophthalmic
laser and operative surgical procedures are highly effective treatment
for diabetic retinopathy. If you have additional questions or would like
further information, contact the general physicians at the Gailey Eye
Clinic.
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