Diabetes is a leading cause of blindness in Canada. People with diabetes are more likely to develop cataracts at a younger age and are twice as likely to develop glaucoma, but diabetes’ effect on the retina is the main threat to vision.
Called diabetic retinopathy, this effect of diabetes on the eyes is the most common cause of blindness in people under age 65 and the most common cause of new blindness in North America. It is estimated that approximately 2 million individuals in Canada (i.e. almost all people with diagnosed diabetes) have some form of diabetic retinopathy.
We are pleased to announce that the Canadian Diabetes Association and the Canadian Association of Optometrists have partnered to help optometrists educate their patients about retinopathy.
What is retinopathy?
Over time, diabetes can cause changes in the retina at the back of the eye. Your retina helps you see by acting like a film projector in the back of your eye, projecting the image to your brain. The change is called retinopathy and there are a couple of different types that affect people with diabetes. The macula, which is the part of your retina that helps you to see colour, becomes swollen (macular edema) and this can cause blindness. A second complication is the growth of new weak blood vessels that break and leak blood into your eye so the retina cannot project images to your brain (proliferative diabetic retinopathy). The result is a loss of sight.
Diabetes causes changes in the tiny blood vessels that nourish the retina. In the early stages, known as nonproliferative or background retinopathy, the arteries in the retina weaken and begin to leak, forming small, dot-like hemorrhages (blood flow from the ruptured blood vessel). These leaking vessels often lead to swelling (edema) in the retina and decreased vision. At this stage, vision may be normal or it may have started to blur or change. About one in four people with diabetes experience this problem.
When retinopathy advances, the decreased circulation of the blood vessels deprives areas of the retina of oxygen. Blood vessels become blocked or closed, and parts of the retina die. New, abnormal, blood vessels grow to replace the old ones. They grow along the retina and along the surface of the vitreous (the transparent gel that fills the inner portion of the eyeball). Unfortunately, these delicate vessels hemorrhage easily. Blood may leak into the retina and vitreous, causing “floaters” (spots that appear to drift in front of the eyes), along with decreased vision.
This is called proliferative retinopathy, and it affects about one in 20 people with diabetes. It can lead to severe visual loss or blindness. In the later phases of the disease, continued abnormal vessel growth and scar tissue may cause retinal detachment and glaucoma.
Effect of retinopathy
The effect of retinopathy on vision in people with diabetes varies widely, depending on the stage of the disease. Common symptoms can include blurred vision (often linked to blood glucose levels), flashes or sudden loss of vision. However, diabetes may cause other eye symptoms.
Fluid can leak into the center of the macula, the part of the eye where clear, detailed vision occurs. The fluid swells the macula and blurs the vision. Called macular edema, it can occur at any stage, although it is more likely to occur as the disease progresses. About one-half of people with proliferative retinopathy also have macular edema.
Treatment of retinopathy
No treatment is needed for nonproliferative retinopathy, unless there is macular edema. Recommended treatment for those with proliferative or severe nonproliferative retinopathy, vitreous hemorrhage or macular edema, is laser therapy, which helps to shrink the abnormal blood vessels, and/or vitrectomy.
Treatment works better before the fragile, new blood vessels start to bleed, but even if bleeding has started, treatment may still be possible, depending on the amount of bleeding.
Vitrectomy is done if the bleeding occurs in the in the vitreous. Blood is removed from the centre of the eye and replaced with saline. The surgeon may also remove strands of vitreous attached to the retina that create traction and could lead to retinal detachment or tears in the retina.
How do I know if I have retinopathy?
In early stages there may be no symptoms, which is why it is important to have regular eye exams. Symptoms, if present, can include:
Flashes of light in the field of vision
Sudden loss of vision
Blotches or spots in vision
How can I prevent retinopathy?
Retinopathy affects 23 per cent of people with type 1 diabetes and 14 per cent of people with type 2 diabetes on insulin therapy. The good news is that there are steps you can take to catch this complication early and prevent its progress:
Visit your CAO optometrist at least once per year. Your optometrist may recommend you visit more or less frequently depending on your situation.
Maintain optimal blood glucose levels, blood pressure and blood cholesterol.
Know your A1C (a test of your average blood glucose level over three months). Most people with diabetes should aim for a target of 7.0 or less. Talk to your healthcare team about what your target should be.
To prevent disease progression, people with diabetes should manage their levels of blood glucose (sugar), blood pressure and blood cholesterol. Research has shown that maintenance of appropriate blood glucose (sugar) levels results in fewer eye problems. The possibility of eye complications can also be greatly reduced with routine examinations. Many problems can be treated with greater success when caught early. So it is vital to see an experienced eye care professional regularly and keep blood glucose (sugar) levels well managed.
Who should be screened for retinopathy?
Any individual older than 15 with type 1 diabetes should be screened annually beginning five years after the onset of diabetes.
All individuals with type 2 diabetes should be screened at the time of diagnosis.
Women with type 1 or type 2 diabetes or women who hope to become pregnant should be screened before conception, during the first trimester, as needed during pregnancy and within the first year post-partum.
All people with diabetes (both type 1 and type 2) are at risk for diabetic retinopathy. The interval for followup assessments should be tailored to the severity of the retinopathy. In those with no or minimal retinopathy, the recommended interval is one to two years.
For more information about diabetic retinopathy, visit the Canadian National Institute for the Blind (CNIB).
To find a CAO optometrist in your area, visit the Canadian Association of Optometrists.