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Overview
Diabetic retinopathy is a complication of diabetes mellitus
in which long-term exposure to high glucose levels
in the blood has damaged retinal blood vessels.
This results in new growth of abnormal blood
vessels, fluid buildup in the macula (i.e.,
macular edema), inadequate blood supply to the
retina, and possibly blood and fluid leakage into
the retina and the vitreous body.
Diabetic retinopathy is a leading cause of
blindness in the United States. When diagnosed
early in the course of the disease, diabetic
retinopathy can be effectively managed. Annual eye
examinations are essential in diabetic care to
prevent permanently impaired or lost vision.
Stages
Diabetic retinopathy develops in two stages:
nonproliferative and proliferative. Not all
patients with nonproliferative retinopathy advance
to the proliferative stage, but the more severe
the condition, the more likely it will become
proliferative.
Nonproliferative
This is the early stage of the disease, when
damaged capillaries break and leak. Fluid buildup
in the macula (called macula edema) causes blurred
vision. (The macula is located in the center of
the retina and is the structure that renders fine,
detailed vision.)
ProliferativeDuring
this later stage, abnormal, fragile blood
vessels grow in the retina and into the vitreous
body (clear gel-like substance that fills the
chamber between the lens and the retina). This
process is called neovascularization. These
fragile vessels are prone to rupturing and
bleeding into the vitreous body, causing blurred
vision and possibly temporary blindness. If scar
tissue forms, it may pull the retina away from the
back of the eye (called
retinal detachment),
which can result in permanent vision loss. Macular
edema also can occur during this stage.
Incidence and Prevalence
Diabetic retinopathy occurs in about 25–50% of
people with diabetes in the United States and is a
leading cause of blindness.
Risk Factors
People with either type of diabetes mellitus, but
especially Type 1, are at risk for retinopathy.
When Type 1 diabetes coexists with hypertension, a
person may be 4 times as likely to develop
proliferative retinopathy. The duration of
diabetes and the degree of hyperglycemia and
hypertension also affect the risk for diabetic
retinopathy.
Signs and Symptoms
In its earliest stages, diabetic retinopathy
usually does not produce symptoms. Once macular
edema develops, vision blurs. The quality of
vision may fluctuate (alternately worsen or
improve slightly).
Bleeding can also cause vision loss, as the
disease advances. As bleeding and leakage
increase, vision decreases. In severe cases,
vision is so impaired that the patient is only
able to distinguish light from dark in the
affected eye.
Diagnosis
Early detection of diabetic retinopathy is
possible with a dilated fundus examination
performed by an ophthalmologist or an optometrist.
(links) By dilating, or enlarging, the pupil with
medicated eye drops, the practitioner can examine
the back of the eye, or fundus, where the retinal
blood vessels and arteries are located. In a
darkened examination room, the practitioner uses
an ophthalmoscope to focus a beam of light through
the pupil and looks through the instrument’s
magnifying lens to inspect the retina for fluid
buildup, swelling, damaged optic nerve tissue, and
changes in and/or leaking blood vessels.
Fluorescein angiography
is used if macular edema or other retinal problems
are suspected. A small amount of dye is
administered via an intravenous infusion and
photographs of the retina are taken with a special
camera as the dye passes through the blood
vessels.
Treatment
Laser Surgery
The argon laser beam can be used to treat macular
edema and proliferative retinopathy. While the
underlying mechanism of action is somewhat
debatable, argon laser treatment can reduce the
risk of moderate vision loss in patients with
macular edema and reduce the risk for severe
visual loss in patients with proliferative
diabetic retinopathy. Laser treatment may not be
able to reverse visual loss that has already
occurred and may need to be repeated if diabetic
retinopathy progresses.
Neovascularization is stopped and new growth
prevented. Vision loss is stabilized, although
usually not improved. Scatter laser treatment is
not effective if bleeding is severe or if the
retina is detached. There are side effects with
this procedure, including increased difficulty
with night vision and the loss of peripheral
vision.
Vitrectomy
Vitrectomy is performed on patients who are not
candidates for laser surgery because of extensive
bleeding in the eye. Blood, scar tissue, and other
debris that forms in the vitreous body as a result
of advanced retinopathy obscures the path of light
to the retina, resulting in blurred vision.
Removing the vitreous clears vision and may
prevent retinal detachment. (link to condition)
Vitrectomy (link to treatment on retinal
detachment) can be performed on patients with more
severe complications of diabetic retinopathy such
as vitreous hemorrhage or traction retinal
detachment.
Prevention
Patients who maintain good control of their blood
sugar level have a significantly lower risk for
retinopathy. Diagnosing retinopathy early can help
prevent complications and advanced disease.
Patients with diabetes should have regular,
comprehensive eye examinations at least once a
year. If retinopathy has developed, more frequent
exams may be necessary.
To prevent vision loss, people with diabetes
should take the following measures:
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Avoid smoking (can lead to circulatory
problems).
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Have regular eye exams.
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Keep blood glucose levels under control.
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Keep blood pressure under control through diet,
lifestyle changes, or medication.
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Report blurred vision, eye pain, or blood in the
eyes immediately.
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Use prescription eye drops as directed.
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