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Richmond Eye Associates
Eye Health and Disorders
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Diabetic Eye Disease
Diabetes mellitus is the leading
cause of new cases of legal blindness in working age Americans. It is estimated
that 14 million Americans have diabetes, but that only one half of these are
aware of it. This page discusses ocular complications of diabetes, and their
treatment.
Read this important information
before proceeding further:
These sections are not intended to replace the professional examination and
diagnosis by a physician, and they are presented here purely for informational purposes.
All possible diagnoses and treatment options are not covered, and the information
discussed should not be taken as a recommendation to self-diagnose and self-treat a
condition. A misdiagnosed or improperly treated eye condition can result in a permanent
loss of vision, or a permanent loss of function of the eye or visual system. In the case
of any eye problem, seek medical attention promptly. This can include emergency room
treatment, as well as treatment by a medical physician or eyecare provider.
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Topics Include:
For eye anatomy explanations, go to
ANATOMY
Diabetes Mellitus is more than just a problem with the control of the blood sugar. It
is a vascular disease: a disease of the blood vessels. Diabetes can lead to complications
throughout the body, including blood vessel problems in the kidneys, heart, brain, and
eyes. The retina lines the inside surface of the eye and receives and processes visual
information for their transmission to the brain via the optic nerve. The primary source of
blood supply to the retina comes from a single artery, the central retinal artery, which
enters the eye through the optic nerve. Once inside the eye, the artery branches on the
surface of the retina into smaller and smaller vessels to supply all of the retina.
An especially critical part of the retina is the "macula" which serves the
central vision of the eye, or the reading vision. There is a pin-point spot of the macula
called the "fovea" which has the sharpest vision.
The eye is unique in that living blood vessels in the retina can be observed by the
examining physician. A number of problems can arise in the retina as complications of
diabetes. Risk factors for the development of these complications include:
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The type of the diabetes: Type 1 diabetics generally are younger at onset, and require
insulin for survival. Type 2 diabetics are usually older at onset, and the diabetes may or
may not require oral medication or insulin for control.
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The control of the diabetes: It has been found that very tight control of the blood
sugar (and associated hypertension) can reduce the risk of retinal complications (in both
Type 1 and Type 2 diabetics).
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The presence of other medical problems such as increased blood pressure or cholesterol.
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The duration of having diabetes.
It has been found that the longer one has diabetes, that there is more risk for
developing retinal complications:
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After 5 years, 25% of insulin-dependent diabetics have some retinopathy.
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After 10 years, 60% have retinopathy.
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After 15 years of insulin-dependent diabetes, 80% have retinopathy, with 25% having the
more severe "proliferative diabetic retinopathy".
For detailed summaries of published journal articles discussing diabetic eye problems
and the influence of control of diabetes on complications, go to
Eye on Health.
Return to Topic List
The earliest or mildest diabetic effect on the retina is called "background
diabetic retinopathy". This condition can occur in one or both eyes in people with
diabetes. When the ophthalmologist examines the retina (usually after dilation), small
hemorrhages can be seen scattered within the retina. Irregularity of blood vessels, and
mild blockage of blood vessels also can occur. Small dilated blood vessels called
"microaneurysms" commonly occur, and appear as tiny red dots in the retina.
Clear fluid can leak from these microaneurysms and from abnormal damaged blood vessels
into the retina. When this occurs, the retina will swell in thickness like a sponge, and
white deposits, or exudates, can form. This swelling can damage the vision, if present for
a long enough time.
Background diabetic retinopathy can occur in people who are not even aware that they
have diabetes. An ophthalmologist observing such incidental findings during a retinal
examination might suggest an evaluation to look for diabetes being present.
Background diabetic retinopathy itself does not usually damage the vision, but it does
indicate that diabetes is affecting the vascular system of the eye and probably of the
entire body. People with background diabetic retinopathy are usually re-examined in at
least 6 months.
A complication of background diabetic retinopathy, and also of more severe forms of
diabetic retinopathy, is diabetic macular edema. Edema is swelling of the retina. The
macula, as discussed above, is responsible for the sharpest, central vision that a person
has. In diabetic macular edema, clear fluid leaking from damaged blood vessels in the
retina and from microaneurysms causes the retina to swell and thicken. When this occurs in
the macula, the reading or central vision is at risk, and can be lost. Extensive studies
have been undertaken to determine when diabetic macular edema should be
treated, and when it can just be monitored. Sometimes an
additional test called a "fluorescein angiogram"
can be done to help to determine the source and extent of fluid leakage.
A more severe retinal complication of diabetic eye disease is "proliferative
diabetic retinopathy". Fortunately, only a small number of diabetics will develop
this complication, but it is still treatable. Here, the vascular damage to the retina
worsens, with more extensive hemorrhages, abnormal blood vessels, areas of blocked off
blood vessels, and fluid leakage into the retina. The closure of small retinal blood
vessels can become so severe that parts of the retina begin to produce a chemical
(recently identified) that stimulates the growth of NEW blood vessels. This chemical
spreads into the jelly-like material that fills the eye, and can affect many different
parts of the eye.
The new blood vessels which form in response to this chemical are abnormal, frail, and
tend to grow out off of the retinal surface into the vitreous body, which is a
gel-like material that fills most of the eye. They
tend to break and bleed, causing large hemorrhages inside of the eye, and can become
scarred, leading to retinal detachments. In a detachment, the retinal is tented off of the
wall of the eye, being pulled up by these abnormal blood vessels.
This complication of diabetes requires more extensive treatment, and sometimes
intra-ocular surgery done in the operating room. Sometimes blood vessels can block off
supplying the central vision itself. If this occurs, the central vision is lost and cannot
be regained.
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The diagnosis of diabetic eye disease requires dilated retinal eye examinations at
periodic intervals. If there is no retinal complications of diabetes, an annual
examination is suggested. If there are retinal changes present, follow-up examinations
ranging from 1 to 6 months may be necessary. In cases of more severe retinal
complications, an additional test if often done:
A fluorescein angiogram is a test done in the office where a pigmented dye is photographed
as it passes through the retinal blood vessels. For this test, the eyes are dilated, and
initial color photographs are taken of the retina by the photographer. Then, the
fluorescein dye is injected into an arm vein by a physician. This is similar to having
blood drawn. Once the dye is in, the needle is removed, and the photographs are taken. The
dye reaches the eye in a matter of seconds. About 30 photographs are taken between the two
eyes over a 10 minute time span. The film is then developed, and the ophthalmologist
studies the results. Important information about the leakage and blockage of blood vessels
can be gained from this test, as well as the presence of abnormal blood vessels.
Treatment of diabetic
retinal disease:
Many diabetic retinal problems are treated using a laser. The laser casts a tiny spot
of light onto the retina in order to seal leaking blood vessels or to prevent the
formation of abnormal blood vessels. Laser treatment is done as an outpatient operation,
but usually only eyedrop anesthesia is needed. The patient is seated at the laser, and
treatments usually range from 5 to 20 minutes. Sometimes, repeat treatments need to be
done.
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For diabetic macular edema, the laser is used to seal leaking blood vessels which are
causing the retina to swell dangerously. This procedure is called "focal" or
"grid photocoagulation". Studies have identified precise situations when this
condition should be treated. The vision does not need to be reduced before treatment is
done, since the goal of the surgery is to maintain the vision at least at where it is.
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For proliferative diabetic retinal disease, the source of the chemical causing abnormal
blood vessels to grow within the eye must be eliminated. The laser is used to diffusely
treat retinal areas which have lost their blood supply to allow the abnormal blood vessels
to stop growing and shrink down. Sometimes this laser surgery is broken up into several
"sittings".
In cases where extensive bleeding has occurred inside of the eye, or if retinal
detachments have formed, intra-ocular microsurgery is needed to correct the problem. This
is termed a "vitrectomy", and is usually performed by a retinal specialist in
the operating room.
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Other
Complications of Diabetes:
If the blood sugar in diabetes becomes elevated to a very high level (usually over 300)
the natural lens inside of the eye can become affected. The high levels of sugar leach
into the lens, and cause it to begin to swell with fluid. This can cause a shift in a
glasses prescription, often toward farsightedness. Vision can become progressively
blurrier for both reading and distance vision, and usually both eyes are affected. After
the blood sugar is brought under control, the lens may remain swollen for weeks! It may
take up to 6 weeks for the glasses prescription to return to normal in some cases. A
person may have to go through several temporary pairs of glasses in order to function
during this transition.
Cataract
Diabetes is a risk factor for developing cataract, which is a clouding of the lens
within the eye. If this occurs, the vision may become permanently blurred and not
improveable with a change in glasses. Sometimes, cataracts associated with diabetes can be
more rapid to develop and can have more severe glare symptoms. Cataract extraction can
cure the problem, but there is some risk of a flare up of diabetic retinal disease
immediately after surgery. The reason for this is not well understood. Sometimes, cataract
can be so severe that the retina cannot even be examined by the ophthalmologist, and the
cataract may have to be removed just to be able to see or treat the retina.
Diabetes may increase the risk of glaucoma, a disease where usually increased pressure
in the eye damages the optic nerve carrying visual signals from the eye. A more severe
form of glaucoma can occur also, called "neovascular glaucoma". Here, abnormal
blood vessels begin to grow on the iris near the front of the eye. This can occur with
proliferative diabetic retinopathy. If laser surgery is not done to force regression of
the blood vessels, they can continue to grow and can rapidly damage the outflow channels
of the eye. Once these channels are scarred closed, the pressure in the eye can skyrocket
in a form of glaucoma that is very difficult to treat.
Early detection of diabetic eye complications is the key to successful treatment. The
patient with diabetes should watch out for any changes in vision, and keep regular
appointments with an ophthalmologist knowledgeable in the diagnosis and treatment of
diabetic eye disease.
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A person recently diagnosed with diabetes should have a complete eye examination.
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If the retina is free of any diabetic complications, the eye exam should be repeated
annually.
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If there is a blurring of vision, this may indicate that the blood sugar is elevated. If
the blurred vision continues, or if floaters or other symptoms are experienced, the eyes
should be re-examined.
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With active diabetic retinopathy, even if mild, the eyes should be examined at 1 to 6
month intervals.
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Tight control of the blood glucose and associated hypertension is essential to
preventing retinal complications of diabetes. This is true for all types of diabetics,
from diet controlled diabetics to insulin dependent.
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If a patient's medical physician desires to intensively control the diabetes, it may be
necessary to have a retinal examination prior to this change in medical treatment. Some
patients can develop "early worsening" of diabetic retinopathy when very tight
control is begun (and for the first 1 to 2 years). Especially in cases with pre-existing
retinopathy, examinations every 3 months may be necessary to prevent complications from
diabetic retinopathy during this transition.
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Go to
Eye on Health for a detailed discussion of
the advantages of tight glucose and hypertensive control in diabetics.
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Return to Topic List
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