Diabetic retinopathy is a type of diabetic eye disease and is the most common cause of vision loss among people with diabetes. It is also a leading cause of blindness among working-age adults. It involves changes to retinal blood vessels that can cause them to bleed or leak fluid, distorting vision. Diabetic macular edema is a consequence of diabetic retinopathy, which causes swelling in the centre of the retina.
Mild non-proliferative retinopathy
Small areas of balloon-like swelling in the retina’s tiny blood vessels, called microaneurysms, occur at this earliest stage of the disease. These microaneurysms may leak fluid into the retina.
Moderate non-proliferative retinopathy
As the disease progresses, blood vessels that nourish the retina may swell and distort. They may also lose their ability to transport blood. Both conditions cause characteristic changes to the appearance of the retina and may contribute to Diabetic Macular Edema.
Severe non-proliferative retinopathy
Many more blood vessels are blocked, depriving blood supply to areas of the retina. These areas secrete growth factors that signal the retina to grow new blood vessels.
Proliferative diabetic retinopathy (PDR)
At this advanced stage, growth factors secreted by the retina trigger the proliferation of new blood vessels, which grow along the inside surface of the retina and into the vitreous gel, the fluid that fills the eye. The new blood vessels are fragile, which makes them more likely to leak and bleed. Accompanying scar tissue can contract and cause retinal detachment - the pulling away of the retina from underlying tissue, like wallpaper peeling away from a wall. Retinal detachment can lead to permanent vision loss.
Chronically high blood sugar from diabetes is associated with damage to the tiny blood vessels in the retina, leading to diabetic retinopathy. The retina detects light and converts it to signals sent through the optic nerve to the brain. In diabetic retinopathy, blood vessels in the retina leaks fluid or bleeds, distorting vision. In its most advanced stage, new abnormal blood vessels grow on the surface of the retina, which can lead to scarring and cell loss in the retina.
People with all types of diabetes (type 1, type 2, and gestational) are at risk for diabetic retinopathy. Risk increases the longer a person has diabetes. Women who develop or have diabetes during pregnancy may have rapid onset or worsening of diabetic retinopathy.
The early stages of diabetic retinopathy usually have no symptoms. The disease often progresses unnoticed until it affects vision. Bleeding from abnormal retinal blood vessels can cause the appearance of “floating” spots. These spots sometimes clear on their own. But without prompt treatment, bleeding often recurs, increasing the risk of permanent vision loss.
As diabetic retinopathy often goes unnoticed until vision loss occurs, people with diabetes should get a comprehensive dilated eye examination at least once a year. Early detection, timely treatment, and appropriate follow-up care of diabetic eye disease can protect against vision loss.
Vision lost due to diabetic retinopathy is sometimes irreversible. However, early detection and treatment can reduce the risk of blindness by 95%. As diabetic retinopathy often lacks early symptoms, people with diabetes should get a comprehensive dilated eye examination at least once a year. People with diabetic retinopathy may need eye examinations more frequently.
Women with diabetes who become pregnant should have a comprehensive dilated eye examination as soon as possible. Additional examinations during pregnancy may be needed.
For diabetic patients, some other ways to prevent or delay vision loss due to diabetic retinopathy include taking medication as prescribed, staying physically active, and maintaining a healthy diet.
Controlling diabetes slows the onset and worsening of diabetic retinopathy. Other trials have shown that controlling elevated blood pressure and cholesterol can reduce the risk of vision loss among people with diabetes.
Diabetic retinopathy is detected during a comprehensive dilated eye examination that includes:
Visual acuity testing
This eye chart test measures a person’s ability to see at various distances.
Tonometry
This test measures pressure inside the eye.
Pupil dilation
Drops placed on the eye’s surface dilate (widen) the pupil, allowing an eye doctor to examine the retina and optic nerve.
Optical coherence tomography (OCT)
This technique is similar to ultrasound but uses light waves instead of sound waves to capture images of tissues inside the body. OCT provides detailed images of tissues that can be penetrated by light, such as the eye.
A comprehensive dilated eye examination allows the doctor to check the retina for:
If DME or severe diabetic retinopathy is suspected, a fluorescein angiogram may be used to look for damaged or leaky blood vessels. In this test, a fluorescent dye is injected into the bloodstream, often into an arm vein. Pictures of the retinal blood vessels are taken as the dye reaches the eye.
Treatment for diabetic retinopathy is often delayed until it starts to progress to Proliferative Diabetic Retinopathy (PDR), or when diabetic macular edema occurs. People with severe non-proliferative diabetic retinopathy have a high risk of developing PDR and may need a comprehensive dilated eye examination as often as every twp to four months.
Diabetic retinopathy can be treated with several therapies, used alone or in combination.
For decades, PDR has been treated with scatter laser therapy known as panretinal photocoagulation. Treatment involves making 2000 to 3000 tiny laser burns in areas of the retina away from the macula. These laser burns are intended to cause abnormal blood vessels to shrink. Although treatment can be completed in one session, two or more sessions are sometimes required. While it can preserve central vision, scatter laser surgery may cause some loss of side (peripheral), colour, and night vision. Scatter laser surgery works best before new, fragile blood vessels have started to bleed.
Anti-VEGF drugs are injected into the vitreous gel to block a protein called vascular endothelial growth factor (VEGF), which can stimulate abnormal blood vessels to grow and leak fluid. Available anti-VEGF drugs include Avastin (bevacizumab), Lucentis (ranibizumab), and Eylea (aflibercept).
Recent studies have shown that anti-Vascular Endothelial Growth Factor (VEGF) treatment not only is effective for treating diabetic macular edema, but is also effective for slowing progression of diabetic retinopathy, including PDR, so anti-VEGF is increasingly used as a first-line treatment for PDR.
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