What is diabetic
retinopathy?
Diabetic retinopathy is one of several eye
diseases that can affect individuals with diabetes. It most commonly occurs when
an individual’s diabetes is uncontrolled. This disease can cause vision
problems and can lead to blindness. This happens when blood vessels on the
retina (see Figure below), which is the tissue lining the inner eye, are
damaged. Some individuals may have blood vessels that swell and leak, others
may have small blood clots or occlusions in their blood vessels, and others may
have new blood vessels forming on their retina.
There are 2 other eye diseases that may also be
common in individuals with diabetes. One is cataracts, which is clouding of the
lens of the eye. Another is glaucoma, which is increased pressure inside of the
eye. These conditions can also lead to vision loss and even blindness.
The Figure
above shows the anatomy of the eye. The retina is the tissue that lines the inner
part of the eye. It contains many blood vessels, which allow blood to carry
oxygen to the eye. It also contains rods and cones, which are responsible for
our vision. The macula is an area near the back of the eye that is responsible
for our sharp, central vision. Parts of the retina that do not contain the
macula help us see peripherally, or to the sides. The fluid inside the eye is
known as vitreous humor or gel.
How many
people are affected by this condition?
·
Most
individuals diagnosed with type 1 diabetes as children will develop diabetic retinopathy
when they are 20 to 40 years old.
·
Approximately
20% of individuals who are newly diagnosed as having type 2 diabetes already
have diabetic retinopathy. These individuals often have had diabetes for years,
however, due to lack of symptoms, they have gone undiagnosed. Unfortunately, by
the time they are diagnosed, the damage to the eye may have already occurred.
·
Within
20 years of being diagnosed with type 2 diabetes, about 60% of individuals will
develop diabetic retinopathy.
What types
of diabetic retinopathy are there?
·
Nonproliferative
diabetic retinopathy (NPDR) accounts for approximately 80% to 95% of diabetic
retinopathies. Nonproliferative means that no new blood vessels are forming on
the retina. However, blood vessels already present are often enlarged and
become leaky. This can lead to fluid, blood, and debris from cells leaking into
the eye. This disease can progress and cause more problems. Advanced
nonproliferative (maculopathy) often presents as swelling of the macula (called
macular edema) and lesions, or areas of damage, on the retina. The macula is an area on the retina
that is responsible for much of our vision, and macular edema is the often the
cause of blindness in patients with diabetes. Within 5 years, approximately 5%
to 20% of individuals with macular edema will be considered legally blind.
·
Proliferative
diabetic retinopathy (PDR) accounts for approximately 5% to 10% of diabetic retinopathy.
This involves neovascularization, or new growth of blood vessels, on the
surface of the retina. Within 5 years 50% of these individuals are diagnosed as
legally blind.
What are
the common signs and symptoms that are associated with diabetic retinopathy?
Most individuals do not have any signs or
symptoms of diabetic retinopathy until it is too late to correct the vision
loss that may have already occurred. Diagnosing the disease early, through
periodic eye exams, can help to slow the progression of the disease. It is
important to identify changes to the eye early in order to take steps to stop
any further damage. Some of the symptoms that may be experienced include:
-
Blurry vision
-
Dark or floating spots
-
Trouble seeing things that are at
the center of your focus when reading or driving
-
Trouble telling colors apart
What are
the common causes or risk factors for diabetic retinopathy?
Risk factors include:
-
Presence
of type 1 diabetes
-
Having diabetes for a long time: The longer someone has
diabetes, the more likely they are to get diabetic retinopathy, and it has been
shown that the risk begins to increase after an individual has had type 2
diabetes for more than 4 years.
- High A1C levels: A1C
levels above the American Diabetes Association goal of <7% indicate uncontrolled
diabetes over a 3-month period. The highest risk is with an A1C >12%, but the
risk is increased with all levels above goal. Diabetic retinopathy is rare in
individuals with an A1C <7 span="">
-
High
blood pressure: Having high blood pressure that is uncontrolled, as determined
by your doctor, can lead to further damage to the blood vessels of the eye.
-
Pregnancy:
Diabetic retinopathy can worsen in approximately 16% to 85% of pregnant women
with preexisting diabetes.
What are
the current recommendations for screening for diabetic retinopathy?
- Adults and children aged 10 years or older with type 1 diabetes should have an initial dilated and comprehensive eye examination by an ophthalmologist or optometrist within 5 years after the onset of diabetes.
A comprehensive eye exam
should include:
-
tonometry,
which measures pressure in the eye
-
visual
field test, which measure your peripheral or side vision
-
visual
acuity test, which tests how well you can see at a variety of distances.
- Shortly after being diagnosed with type 2 diabetes, individuals should have a dilated and comprehensive eye examination.
- Individuals with either type 1 or type 2 diabetes should have annual eye exams. If one or more eye exams are found to be normal, the ophthalmologist or optometrist may allow less frequent exams (every 2 to 3 years). If it is found that retinopathy is getting worse, more frequent examinations will be required.
- Women with preexisting diabetes who are planning a pregnancy or who have become pregnant should have a comprehensive eye examination. It is also important that those individuals are counseled on the possible development and/or worsening of diabetic retinopathy during pregnancy. Eye examinations should occur in the first trimester with close follow-up throughout pregnancy and for 1-year postpartum.
Why is
early diagnosis important?
As stated above, most individuals do not have
any signs or symptoms of retinopathy until it is too late to correct the damage
that has been done. Diabetic retinopathy is the most common cause of new
blindness in adults between the ages of 20 and 74 years in the United States.
What tests
are done for the diagnosis of diabetic retinopathy?
·
Dilated eye exam: The
ophthalmologist or optometrist gives the individual eye drops to make their
pupils dilate or open. This makes it easier to see the inside of the eye and
back to the retina.
- Digital retinal imaging: For this test, pictures of the eye are taken with a special camera and the pictures are looked at by the ophthalmologist or optometrist. They look for anything that is abnormal on the retina, such as spots or new blood vessels.
- If either the dilated eye exam or the digital retinal imaging test shows a problem, the doctor might suggest other tests also.
- Stereoscopic color fundus photographs are pictures of the interior of the eye that can help detect anything that is not normal.
- Fundus photographs can detect eye damage and should be performed along with the dilated eye exam and digital retinal screening at least at the first appointment.
- Fluorescein angiography: Fundus photographs may miss macular edema or proliferative diabetic retinopathy, so another test called fluorescein angiography is performed. A fluorescein dye is injected into a vein and photographs are taken that track how the dye travels in the retina. It can detect if the blood vessels are blocked or if they are leaking.
What
treatments are available for diabetic retinopathy?
- Controlling risk factors such as high blood pressure, high cholesterol, and uncontrolled diabetes are important in the prevention of diabetic retinopathy as well as in the management of the disease.
- Laser photocoagulation is a laser surgery that is used to stop blood vessels in the retina from leaking or growing.
-
Focal
laser photocoagulation: Used in individuals with macular edema, focuses on a specific area.
-
Panretinal
photocoagulation: Used mostly in individuals with proliferative diabetic
retinopathy, and sometimes for individuals with severe nonproliferative
diabetic retinopathy, includes most parts of the retina.
-
Focal photocoagulation is preferred as first-line treatment to
minimize worsening of macular edema that may occur after panretinal
photocoagulation.
- A vitrectomy is a surgery that is used to remove blood from the fluid in the eye (the vitreous humor). This is done when blood vessels in the retina leak into the fluid. It is most helpful in proliferative diabetic retinopathy.
- Anti-vascular endothelial growth factors (VEGF) are used for macular edema as an additional option. What these medications do is stop new blood vessels from forming. Anti-VEGF medications include bevacizumab, ranibizumab, and pagaptanib.
- Macular edema that is not improved by other means may be treated with intravitreal steroid injections, which are injections directly into the fluid in the eye, to improve visual outcomes. A few of the steroids used are triamcinolone, fluocinolone, and dexamethasone.
- It is important to discuss all treatment options with your doctor to determine which is best for you.
What can individuals
do to prevent this condition?
It is important to
discuss any prevention techniques with your doctor so they can tailor your
therapy for you. Different diet options, exercise regimens, and goal blood
glucose levels may not be right for everyone.
- Intensive control of blood sugar is important in the prevention of diabetic retinopathy, however, it does not guarantee that a individual will not develop the disease. Factors that can influence an individual’s control of their blood sugars include adhering to a diet and exercise plan determined by your doctor, being compliant with prescribed medications, and glucose monitoring, as well as keeping scheduled doctors visits. One can reduce their risk of retinopathy by 35% per 1 percentage point reduction in A1C.
Current recommendations
from the American Diabetes Association are:
-
A1C
< 7%
-
Fasting
(before a meal) blood glucose 70 to 130 mg/dL
-
Postprandial
(1 to 2 hours after a meal) glucose < 180 mg/dL
·
Tight
blood pressure control is also important in the prevention of developing the
disease and also the progression of the disease. Current American Diabetes
Association guidelines recommend a goal blood pressure of less than 140/80 for individuals with
diabetes.
·
Intensive
cholesterol control may not have as big an impact as glucose and blood pressure
control, but is still be important in the prevention and management of diabetic
retinopathy. Current American Diabetes Association guidelines recommend an HDL greater than 50 mg/dL for women and greater than 40 mg/dL for men, and triglycerides less than 150 mg/dL. The goal LDL for individuals
who do not have cardiovascular disease, as determined by your doctor, is less
than 100 mg/dL, and a goal of less than 70 mg/dL for those diagnosed with
cardiovascular disease.
Where can
I find more information on diabetic retinopathy?
- National Eye Institute's information for individuals can be found at http://www.nei.nih.gov/health/diabetic/eye disease.asp.
- American Diabetes Association information about eye complications can be found at http://www.diabetes.org (in both English and Spanish).
Written
by: Tiffany
Chaddick
Doctor of Pharmacy Candidate
College of Pharmacy, University of Illinois at Chicago
UIC Pharmacy
August 2013
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