The prevalence of diabetic retinopathy is 40 percent and occurs more frequently in type 1 diabetes, the threat for vision occurs in 10 percent of cases.
Diabetic proliferative retinopathy affects 5-10% of the diabetic patients. Patients with type 1 diabetes have a 60% risk of proliferative diabetic retinopathy at 30 years.
Causes of diabetic retinopathy
There are three basic components of this damaging process.
– the blood vessels can leak
– they can make a special growth substance that makes other vessels grow (VEGF = vascular endothelial growth factor)
– the vessels may eventually close and block.
The leakage causes the retina to swell up a little and become waterlogged, a bit like a sponge. This swelling then damages the retinal cells themselves. This is the main mechanism in ‘maculopathy’ and ‘macula edema’. At the same time control of the blood flow to the retina is faulty, and blood flow to the retina increases. This naturally increases the retinal leakage further.
The tiny blood vessels may eventually close and block. If the retina is badly damaged by leakage or very severe diabetes, the blood vessels may close up, and nutrients will not reach the retinal cells. This happens in ‘ischemic’ macular disease.
In diabetic proliferative retinopathy very small blood vessels grow from the surface of the retina.
As the retina is damaged by diabetes, the diseased retina releases special growth chemicals. These chemicals make tiny blood vessels grow: these are called ‘new blood vessels’.
Diabetic retinopathy – signs
- retinal hemorrhages
- macula edema
- focal maculopathy
- diffuse maculopathy
- ischemic maculopathy
– longstanding diabetes
– poor blood glucose control
– arterial hypertension
Other risk factors: hyperlipidemia, smoking, cataract surgery, obesity, anemia
– factors of poor prognosis:
Ocular: severe ocular ischemia, exudates, diffuse macula edema, severe retinopathy at first attendance.
Systemic: uncontrolled hypertension, renal disease, poor blood glucose control, elevated HbA1 – glycosylated hemoglobin
Diagnosis of diabetic retinopathy
Diagnosis is done through examination of eye fundus by direct or indirect ophthalmoscopy.
Treatment of diabetic retinopathy
Pharmacologic therapy of diabetic retinopathy is used to reduce diabetic macular edema and neovascularization of the disc or retina. However, these medications cannot stop disease progression and are used as complementary methods.
One of the most efficient treatments is laser retinal coagulation. This involves directing a high-focused beam of light energy to create a coagulative response in the target tissue and destroy newly formed vessels with increased wall permeability, narrow areas where capillaries are blocked. During the treatment, the patient should be monitored by the ophthalmologist.
When laser photocoagulation in PDR is precluded in the presence of an opaque media, such as in cases of cataracts or vitreous hemorrhage, cryotherapy may be applied instead.
In selected patients surgical treatment is indicated.
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