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What Is Diabetes?
About one person in fifty in the USA is affected by diabetes mellitus or
'sugar diabetes'. This means that the body cannot cope normally with sugar
and other carbohydrates in the diet.
Diabetes can start in childhood, but it often begins later in life. It can
cause complications which affect different parts of the body. There are two
types of diabetes mellitus - one is controlled by insulin injections, and
the other by diet or tablets, but they both affect the eyes in the same way.
If you have diabetes this does not necessarily mean that your sight will be
affected, but there is a higher risk. If your diabetes is well controlled
then you are less likely to have problems, or they may be less serious.
However if there are complications which affect the eyes then this can
result in loss of sight.
People with diabetes face a risk of eye disease that can cost them their
sight if they don't get regular eye exams. The disease is called diabetic
retinopathy, and it's a leading cause of blindness and visual impairment in
the world.
Although it's not clear whether diabetic retinopathy can be prevented, it
can be slowed -- and vision preserved -- by laser or other surgical
treatment. For best results, treatment must be given at particular times
during the course of the disease. For that reason, regular medical attention
is important.
Most sight loss from diabetic retinopathy can be prevented. But it is vital
that it is diagnosed early. You may not realize that there is anything wrong
with your eyesight, and so regular eye checks are extremely important.
How Can Diabetes Affect The Eye?
Your eye has a lens and an aperture (opening) at the front, which adjust to
bring objects into focus on the retina at the back of the eye.
The retina is made up of a delicate tissue that is sensitive to light,
rather like the film in a camera.
At the center of the retina is the macula which is a small area about the
size of a pinhead. This is the most highly specialized part of the retina
and it is vital because it enables you to see fine detail and read small
print. The other parts of the retina give you side vision (peripheral
vision). Filling the cavity of the eye in front of the retina is a clear
jelly-like substance called the vitreous humor.
Diabetes can affect the eye in a number of ways. These usually involve the
fine network of blood vessels in the retina - hence the term diabetic
retinopathy.
Temporary Blurring. Your vision may become blurred for a few days or weeks while your diabetes is first being controlled. This is due to the swelling of the lens of the eye and will soon clear without treatment soon after the diabetes is controlled.
Cataract. This can occur in two forms:
- young people with diabetes very occasionally develop a special type of
cataract. Although their vision gets worse, it can be restored by
surgery.
- older people with diabetes can be especially prone to developing
cataracts. Cataracts can be successfully removed by surgery and usually
it is possible to insert a lens implant. However this is unsuitable for
some people and you will be told if this is the case.
Blood Vessel Damage. Retinopathy results from damage to microscopic blood vessels in the retina,
the light-sensing membrane in the back of the eye. Diabetes damages blood
vessels in the eye, just as it does those in the heart, kidneys and other
areas of the body, although researchers aren't sure how.
Retinopathy
In retinopathy, blood vessel linings weaken, sometimes bulging out to form
tiny aneurysms -- sac-like dilations in the vessel wall. The microaneurysms
and vessels then begin to leak fluid into the retina, causing it to thicken.
At this early stage, called background retinopathy, sight may not be
affected. But if the retinal swelling (edema) affects the center of the
macula (the central part of the retina that's responsible for detailed
vision), reading and other close work may become difficult.
As diabetes damages the blood vessels, they may leak fluids, fats. protein
and blood. Not infrequently, such leakage creates fluid accumulations in the
macular region. This causes swelling of the retina and blurred, impaired
vision.
The changes that take place in background retinopathy may set the stage for
a more serious form of disease called proliferative retinopathy.
At this point, new blood vessels begin growing on the surface of the retina.
These vessels are also fragile and frequently bleed into the vitreous, the
jelly-like substance inside the eye.
Such hemorrhages can have a devastating effect on vision. Vision may become
blurred, distorted, or partially or even totally blocked.
Scar tissue often grows along with the new blood vessels. As this tissue
contracts, it may pull the retina off the back of the eye. Unless treated
immediately, retinal detachment can cause severe loss of sight or blindness.
The blood vessel changes that occur in retinopathy aren't visible without
special instruments. And because the retina has no pain receptors,
retinopathy isn't painful.
The disease begins and may progress without warning until a person notices a
blurring or even a total block in vision. That's why regular eye exams are
so important for diabetics.
The longer a person has diabetes, the more likely it is that he or she will
develop retinopathy. About half of those who've been insulin dependent for
14 years have some vascular damage in the retina. Thus, retinopathy is more
common in people with juvenile-onset diabetes than in those with adult-onset
diabetes.
Nonetheless, it's just as important for people with adult- onset disease to
have regular eye exams because their diabetes may have begun several years
before it was diagnosed.
Treatments
Background retinopathy that isn't affecting sight isn't treatable. But the
disease will need to be watched closely at that point.
Close monitoring allows vision-threatening changes, such as macular edema
and proliferative retinopathy, to be detected and treated immediately to
prevent irreversible vision loss. Surgical treatments can prevent
deterioration of vision in 60% of patients.
Laser surgery is the standard procedure used to stop or reverse damaging
changes in blood vessels. The treatment works by sealing off, or
photocoagulating, bleeding vessels.
The laser also can be used to stop abnormal blood vessel growth. In a
technique called "scatter photocoagulation," several small burns are made
around the perimeter of the retina, where they have little effect on vision.
By reducing the amount of retinal tissue that uses oxygen, the treatment
allows the more important, central part of the retina to receive the oxygen
it needs. Therefore, new blood vessels with the potential to cause problems
are less likely to form there.
Laser surgery usually is performed by subspecialists in retinal surgery, who
can do the procedure in their offices. In severe cases of retinopathy, a
surgical procedure called vitrectomy can improve sight.
Vitrectomy removes blood that has leaked into the vitreous. The procedure
improves vision in many people, but not without some risk. Various
complications occur in 25% of the procedures. Vitrectomy is performed in a
hospital operating room, often on an outpatient basis.
Physicians don't yet know whether patients can do anything to prevent
retinopathy or keep it from getting worse. More and more evidence suggests
that controlling blood sugar might be the key. As yet, however, the success
of this strategy hasn't been proved.
The best a patient can do is to try to control blood sugar as well as
possible. That includes dieting, watching sugar intake and monitoring blood
sugar levels.
Regular eye exams are the most important consideration.
People with diabetes should visit an ophthalmologist once a year. Although
retinopathy may develop, with proper medical attention it doesn't have to
mean a significant loss in vision.