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People
with diabetes can develop complications that affect
their vision. High
blood sugar causes damage to the blood vessels in the
retina. Normally,
these blood vessels are watertight; but, in patients
with longstanding diabetes, leaky areas can develop. This allows f luid to seep into the retina. Macular
Edema is the swelling caused by this fluid. This swelling causes vision to worsen. Treating the edema in the retina can often lead to
improvement or preservation of vision. Laser treatment is often used.
A
second problem that may occur in those with longstanding
diabetes is called Retinal
Nonperfusion. In
a normal eye, tiny blood vessels called capillaries
carry oxygen and nutrients to the retina. In this complication, the capillaries close, and the retina
is deprived of the oxygen and nutrients it needs. This condition is not reversible with laser
treatment.
These
complications of diabetes are more common in people who
have poor medical control of their diabetes. Good control of diabetes is important to preserve vision. The result of good management of diabetes is not
dramatic or even noticeable over the short term. However, the odds of preserving your vision over the long
term are greatly improved by good medical control not
only of blood sugar levels, but also of high blood
pressure, serum cholesterol and kidney disease, if these
are also present.
The
main treatments for diabetic macular edema are two types
of laser procedures: focal laser and grid
photocoagulation. Focal
laser is the most common treatment. Local areas of leakage, called microaneurysms,
are treated directly with the laser in an effort to
cauterize and close the leaking spots. This is usually done with a yellow laser, and the
results are generally fairly effective. Grid photocoagulation is generally used in cases where the location of the
leaks is not clear. The laser treatment is placed in such a way as to
change the blood circulation in the retina, and this
reduces the swelling. This method is not as effective as focal
treatment, and the outcome is more guarded.
Both of
the laser treatments can generally be done in the
clinic. A
topical anesthetic is applied before the lasering is
done. Usually,
there will be some blurring or worsening of vision for
one to two weeks. It
may take one to three months before visual improvement,
if it is to occur, is evident. After three or four months, the response to the treatment can
be evaluated, prior to considering additional treatment. In some people, the benefit of laser procedures
is overwhelmed by the severity of the leakage, and
vision loss occurs despite thorough laser treatment.
While the laser is the standard treatment for diabetic macular edema, the use of intraocular drugs is increasing due to established safety and efficacy in reducing macular edema and improving vision. Triamcinolone (Kenalog™) is a steroid that is used as an adjunct for treatment of macular edema. This medication stabilizes leaky blood vessels and reduces edema very well, although the effect can be
transient. The medication has a very tiny risk of infection and a somewhat higher though still small risk of glaucoma when used. This is a medication that can be useful when laser treatment is no longer effective. Your doctor will discuss this with you.
Surgical treatment for diabetic macular edema is used, albeit rarely. In some settings of diabetic macular edema, usually if laser has failed to reduce the edema, surgery may be beneficial. In some patients, the vitreous jelly is stuck or adherent to the retina, and traction from this jelly prevents laser from reducing fluid leakage. Surgery can be helpful in this setting. This is not common, and the surgeon will discuss this in detail.
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