If you have diabetes mellitus, your body does not use and store
sugar properly. High blood-sugar levels can damage blood vessels
in the retina, the nerve layer at the back of the eye that senses
light and helps to send images to the brain. The damage to retinal
vessels is referred to as diabetic retinopathy.
Types of diabetic retinopathy
There are two types of diabetic retinopathy: nonproliferative
diabetic retinopathy (NPDR) and proliferative diabetic
NPDR is an early stage of diabetic retinopathy.
In this stage, tiny blood vessels within the retina leak blood or
fluid. The leaking fluid causes the retina to swell or to form deposits
Many people with diabetes have mild NPDR, which may not affect
their vision. When vision is affected it is the result of macular
edema and/or macular ischemia.
Macular edema is swelling, or thickening,
of the macula, a small area in the center
of the retina that allows us to see fine details clearly.
The swelling is caused by fluid leaking from the retinal blood
vessels. It is the most common cause of visual loss in diabetes.
Vision loss may be mild to severe, but even in the worst cases,
peripheral vision continues to function.
Macular ischemia occurs when small blood
vessels (capillaries) close. Vision blurs because the macula
no longer receives sufficient blood supply to work properly.
PDR is present when abnormal new vessels
(neovascularization) begin growing on the surface of the
retina or optic nerve. The main cause of PDR is widespread closure
of retinal blood vessels, preventing adequate blood flow. The retina
responds by growing new blood vessels in an attempt to supply blood
to the area where the original vessels closed. Unfortunately, the
new, abnormal blood vessels do not resupply the retina with normal
blood flow. The new vessels are often accompanied by scar tissue
that may cause wrinkling or detachment of the retina.
PDR may cause more severe vision loss than NPDR because it can
affect both central and peripheral vision. Proliferative diabetic
retinopathy causes visual loss in the following ways:
Vitreous hemorrhage: The fragile new vessels
may bleed into the vitreous, a clear, jelly-like substance
that fills the center of the eye. If the vitreous hemorrhage
is small, a person might see only a few new dark floaters.
A very large hemorrhage might block out all vision.
It may take days, months or even years to resorb the blood,
depending on the amount of blood present. If the eye does
not clear the vitreous blood adequately within a reasonable
amount of time, vitrectomy surgery may be recommended. Vitreous
hemorrhage alone does not cause permanent vision loss. When
the blood clears, visual acuity may return to its former level
unless the macula is damaged.
Traction retinal detachment: When PDR is
present, scar tissue associated with neovascularization can
shrink, wrinkling and pulling the retina from its normal position.
Macular wrinkling can cause visual distortion. More severe
vision loss can occur if the macula or large areas of the
retina are detached.
Neovascular glaucoma: Occasionally, extensive
retinal vessel closure will cause new, abnormal blood vessels
to grow on the iris (colored part of the eye) and block the
normal flow of fluid out of the eye. Pressure in the eye builds
up, resulting in neovascular glaucoma, a severe eye disease
that causes damage to the optic nerve.
How is diabetic retinopathy diagnosed?
A medical eye examination is the only way to find changes inside
your eye. An ophthalmologist can often diagnose and treat serious
retinopathy before you are aware of any vision problems. The ophthalmologist
dilates your pupil and looks inside of the eye with an ophthalmoscope.
If your ophthalmologist finds diabetic retinopathy, he or she may
order color photographs of the retina or a special test called fluorescein
angiography to find out if you need treatment. In this
test a dye is injected in your arm and photographs of your eye are
taken to detect where fluid is leaking.
How is diabetic retinopathy treated?
The best treatment is to prevent the development of retinopathy
as much as possible. Strict control of your blood sugar will significantly
reduce the long-term risk of vision loss from diabetic retinopathy.
If high blood pressure and kidney problems are present, they need
to be treated.
Laser surgery: Laser surgery is often
recommended for people with macular edema, PDR and neovascular
glaucoma. Each condition is treated with a different type
of laser surgery.
For macular edema, the laser is focused on the damaged retina
near the macula to decrease the fluid leakage. The main goal
of treatment is to prevent further loss of vision. It is uncommon
for people who have blurred vision from macular edema to recover
normal vision, although some may experience partial improvement.
A few people may see the laser spots near the center of their
vision following treatment. The spots usually fade with time,
but may not disappear.
For PDR, the laser is focused on all parts of the retina
except the macula. This panretinal photocoagulation
treatment causes abnormal new vessels to shrink and often
prevents them from growing in the future. It also decreases
the chance that vitreous bleeding or retinal distortion will
Multiple laser treatments over time are sometimes necessary.
Laser surgery does not cure diabetic retinopathy and does
not always prevent further loss of vision.
Vitrectomy: In advanced PDR, the ophthalmologist
may recommend a vitrectomy. During this microsurgical procedure,
which is performed in the operating room, the blood-filled
vitreous is removed and replaced with a clear solution. The
ophthalmologist may wait for several months or up to a year
to see if the blood clears on its own before performing a
Vitrectomy often prevents further bleeding by removing the
abnormal vessels that caused bleeding. If the retina is detached,
it can be repaired during the vitrectomy surgery. Surgery
may be done earlier if there is macular distortion or a traction
retinal detachment. The longer the macula is distorted or
out of place, the more serious the vision loss can be.
Vision loss is largely preventable
If you have diabetes, it is important to know that with today’s
improved methods of diagnosis and treatment, only a small percentage
of people who develop retinopathy have serious vision problems.
Early detection of diabetic retinopathy is the best protection against
loss of vision. You can significantly lower your risk of vision
loss by maintaining strict control of your blood sugar and visiting
your ophthalmologist regularly.
When to schedule an examination
People with diabetes should schedule examinations at least once
a year. More frequent medical eye examinations may be necessary
after the diagnosis of diabetic retinopathy.
Pregnant women with diabetes should schedule an appointment in
the first trimester because retinopathy can progress quickly during
If you need to be examined for glasses, it is important that your
blood sugar be in consistent control for several days when you see
your ophthalmologist. Glasses that work well when the blood sugar
is out of control will not work well when sugar is stable.
Rapid changes in blood sugar can cause fluctuating vision in both
eyes even if retinopathy is not present.
You should have your eyes checked promptly if you have visual changes
Affect only one eye;
Last more than a few days;
Are not associated with a change in blood sugar.
When you are first diagnosed with diabetes, you should have your
Within five years of the diagnosis if you are 30 years
old or younger;
Within a few months of the diagnosis if you are older than