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Proliferative
Diabetic Retinopathy is a serious complication of
diabetes. In
this situation, diabetes-related damage to the blood
vessels of the retina leads to the secretion of a
substance called vascular endothelial growth factor (VEGF). VEGF causes abnormal blood vessels to grow on the
surface of the retina. These vessels  bleed easily and may also pull on
the retina, causing retinal traction. The growth of these new blood vessels (a process
called neovascularization) is a particularly dangerous
problem. The
vessels can often grow to the point where they can
threaten vision without the individual knowing there is
anything wrong. The
person affected may become aware of the problem only
when the vessels bleed or create a retinal detachment. By then, it may be too late to prevent having
surgery or suffering a permanent loss of vision. This is one of the reasons it so important for
diabetics to have eye examinations at regular intervals.
When
the abnormal blood vessels leak, the blood ends up in
the vitreous cavity, which is the middle section of the
inside of the eye. The spots of blood may look like little specks,
bugs, or floaters. If a lot of bleeding has occurred, vision can be
greatly reduced. If you have diabetes and suddenly see a large number of
floaters in an eye, you should notify your eye doctor
right away.
A laser
procedure called panretinal photocoagulation is the main treatment for proliferative
diabetic retinopathy. In this approach, wide areas of the peripheral
(side) retina are treated in a nonspecific pattern of
laser spots. This
changes the blood vessel circulation of the eye and
improves the delivery of oxygen to the retina. This leads to less VEGF being produced and fewer
new abnormal blood vessels being created. Occasionally, the abnormal blood vessels can be
treated directly, but generally, the treatment is
delivered in a random pattern. This treatment is quite extensive and often
requires a retrobulbar anesthetic to prevent the
treatment from being too painful. One or more sessions may be needed to complete
this treatment. Often
patients have pain for a day or two after treatment,
which is usually manageable with non-narcotic drugs. Vision is typically more blurred for a week or
two after treatment, then goes back to what is was
before the leaking occurred. It is not rare for bleeding to occur after treatment because
it takes several weeks for the regression of the
neovascularization to occur. Some peripheral (side) vision and some night
vision may be lost as a consequence of panretinal
photocoagulation. In
general, the benefit far exceeds this small vision loss.
Laser
treatment for proliferative diabetic retinopathy is one
of the most effective treatments in all of medicine. This therapy has saved the vision of millions of
patients and is truly a modern marvel. Nevertheless, in some patients, continued growth of abnormal
blood vessels and bleeding from them occurs despite good
laser treatment. If
a patient has hemorrhages that are minimal and clear
rapidly, often these can be left untreated with no harm. If a patient has a massive hemorrhage with
substantial loss of vision, surgery is likely to be
required to treat the problem. If the growth of abnormal blood vessels leads to
tractional retinal detachment, this is a grave
situation, and surgery will be necessary. In general, eyes followed closely and treated
early for neovascularization stabilize and do well for
the long term. A
small percentage of patients have such poor blood flow
that vision is lost despite excellent treatment.
Bevacizumab (Avastin™) is a genetically engineered antibody to VEGF that rapidly causes abnormal blood vessels to regress. This can be injected intravitreally and be very beneficial in the management of certain patients with complications from proliferative diabetic retinopathy. In general, patients with low to moderate risk proliferative diabetic retinopathy do not need this drug, but patients who have very high risk problems or additional problems such as rubeosis can benefit greatly from this treatment. As more evidence of this drug’s benefit accrues, this may become a more common treatment.
Because
of the very high risk of vision loss from proliferative
diabetic retinopathy, and because this process can be
ongoing with no symptoms, it is very important for
diabetics to have examinations at intervals recommended
by their eye doctors.
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