Diabetes
causes abnormalities in blood vessels throughout
the body. Because the eye has a rich blood supply,
it is particularly prone to complications of diabetes.
This page will explain the types of diabetic eye
disease and their treatment.
What is the retina?
The retina is the nerve tissue that lines the back wall of the eye. Much like
the film in a camera, the retina is sensitive to light. It transforms light
energy to nerve stimuli, and “sends a picture” through the optic
nerve to the brain. The macula is a specialized area in the central part
of the retina. Because of the abundance of nerve connections that serve the
macula, it is the part of the retina that provides for sharp, clear color
vision. Our ability to read and see fine detail depends upon the health of
the macula. Unfortunately, it is frequently affected by abnormalities of
blood vessels in diabetes.
TYPES OF DIABETIC RETINOPATHY
They are two types of diabetic retinal disease: diabetic maculopathy and proliferative
diabetic retinopathy.
Diabetic Maculopathy
In diabetic maculopathy, fluid rich in fat and cholesterol leaks out of damaged
vessels. If the fluid accumulates near the center of the retina (the macula)
there will be distortion of central vision. If too much fluid and cholesterol
accumulate in the macula, they can cause permanent loss of central vision.
Proliferative Diabetic Retinopathy
Proliferative diabetic retinopathy involves the formation of abnormal blood
vessels. These develop when some of the retinal blood vessels become clogged,
and sections of the retina are deprived of oxygen and nutrients. In an attempt
to heal itself, the retina signals the body to form new blood vessel in the
damaged retina. Unfortunately, these new vessels, called neovascularization,
are fragile and frequently bleed into the vitreous. This vitreous blood blocks
light from reaching the retina and can cause scar tissue to develop. The
scar tissue, in turn, can pull on the underlying retina and cause it to separate
or detach from the wall of the eye. This condition, called traction retinal
detachment, is a common cause of blindness in people with diabetes. Some
patients with early proliferative retinopathy will have evidence of abnormal
blood vessel growth, but vision may still be 20/20. Despite the fact that
such an eye may have no symptoms, it is at a significant risk for the development
of severe visual loss. Treatment is most useful in preventing the serious
complications of vitreous hemorrhage and traction retinal detachment at this
early stage.
DIAGNOSIS
In order for the retinal specialist to determine the extent of retinopathy,
a fluorescein angiogram is usually preformed. Fluorescein, a water soluble
dye, is injected into a vein in the arm or hand and a series of photographs
are taken as the dye moves through the retinal circulation. Any weak or abnormal
vessels leak fluorescein, and this is photographed. This test does not use
X-rays and is quite safe. Rarely, patients may be nauseated or have allergic
reactions to the dye. Our office is equipped with medications to deal with
these reactions. If this occurs, be sure to alert your doctor to this reaction
in case the test needs to be repeated in the future.
TREATMENT
Diabetic Maculopathy:
Diabetic maculopathy requires treatment if fluid is leaking into the macula.
The treatment begins with identifying the leaking blood vessels on the Fluorescein
angiogram. Laser treatment can be applied to seal the leaking vessels. The
laser is an intense beam of light which can be finely focused on each individual
leak. Laser is effective in stabilizing or improving vision in 75% of patients
with macular edema. Despite treatment, 25% of patients continue to lose vision
due to recurring leaks. Control of the diabetes and blood pressure is important
in reducing the chances of leaking vessels returning following treatment. The
fluid often takes up to 2 to 3 months to dry up following closure of abnormal
vessels. Visual recovery is slow and gradual. If the fluid persists, the Fluorescein
angiogram is repeated to determine the site of the vessels still leaking and
laser treatment may be repeated. The average patient needs 2-3 laser sessions
per eye to control diabetic maculopathy over the course of their lifetime.
A minority of patients have persistent diabetic macular edema despite adequate
laser treatment. These patients often benefit from intravitreal kenalog
injection.
Proliferative Diabetic Retinopathy:
Proliferative diabetic retinopathy requires urgent laser treatment to prevent
the serious complications of vitreous hemorrhage and traction retinal detachment.
The Fluorescein angiogram is used to identify clogged vessels and damaged
retina. Laser treatment thins the damaged retina and reduces the demand for
oxygen. The abnormal blood vessels then disappear within weeks. Treatment
often requires 2 to 3 sessions per eye, depending upon the extent of the
retinopathy. Treatment is done to preserve the best possible central vision
and involves some permanent loss of night vision and peripheral vision, particularly
if heavy treatment is required. In 10% of patients, there can also be mild
deterioration of central vision. After a few days, the central vision usually
returns to its pretreatment level. Laser treatment is successful in preventing
serious visual loss in 95% of patients. Five percent of patients have progressive
loss of vision, despite treatment.
What the patient should know
Treatment will not bring back perfect vision. If successful, treatment will
prevent further deterioration in visual acuity.
In some cases, significant improvement in central vision can be expected.
With extensive treatment, there may be some loss of side and night vision.
More that one series of treatments may be required.
After PRP treatment, the pupil may remain dilated for several months due to
damage to the nerve that controls the size of the pupil.
Repeated office visits and Fluorescein angiography may be needed.
Control of the diabetes and blood pressure are essential in slowing the progression
of retinopathy and aiding the success of treatment.
Be patient. Improvement usually occurs slowly, over several months.
Although there is no perfect method to prevent
visual loss in diabetes, with current treatment
modalities, the outlook for maintenance of useful
vision is now excellent. Early detection, prompt
treatment, careful follow-up evaluations and good
medical control can be sight saving. |
