Diabetes is a disease that affects your entire body. Body cells require glucose to survive, and normally, glucose (sugar) in the blood is tightly controlled. However, too much or too little glucose in the blood can disturb how the organs function.
The pancreas keeps blood glucose levels within normal range. After a meal, when blood glucose levels rise, the pancreas makes a hormone called insulin. Insulin’s job is to remove glucose from the blood to prevent damaging organs. It signals body cells to take up glucose from the blood.
Diabetic retinopathy damages blood vessels that nourish the retina. The retina, a sensory layer of the eye, changes images passing through the eye’s lens into electric signals. It sends these signals through the optic nerve to the brain.
Many small blood vessels supply the cells of the retina with blood. The blood vessels provide oxygen and nutrients to the cells of the retina, and drain waste products. Unless the cells receive a constant supply of nutrients and oxygen, they begin to die. Your sight is affected as a result.
When diabetes is poorly controlled, these blood vessels can become weaker and leak fluid into the retina. New blood vessels begin to form, but they are fragile and can bleed into the retina and surrounding fluid.
One part of your retina, called the macula, is especially sensitive to light. When you read or look at an object, your macula allows you to identify details and detect small changes in colour and texture. The macula is the most important part of your retina for specialized vision. If blood vessels leak fluid into the macula, your vision may be severely affected.
Ensuring that your blood glucose is tightly controlled slows damage to your retina and prevents severe loss of vision over time. Since your body’s glucose response system is not working properly, you need to keep it as normal as possible.
|Blood glucose level before a meal||• 4.0 to 6.0 mmol/L (normal)
• 4.0 to 7.0 mmol/L (target for those with diabetes)
|Blood glucose level 2 hours after starting a meal||• 5.0 to 8.0 mmol/L (normal)
• 5.0 to 10.0 mmol/L (target for those with diabetes)*
|*If A1C is greater or equal to seven per cent, then target is 5 to 7.0 mmol/L.|
To find out how well you are controlling your blood glucose levels, an A1C test is done with a sample of your blood. Glucose in the blood binds to hemoglobin, a protein found in red blood cells. The glycosylated hemoglobin A1C test is a good measure of your average blood glucose level for the two to three month period before the test is taken. A1C should be measured about every three months.
People with normal blood glucose control usually have a glycosylated hemoglobin
A1C of less than six per cent. People with diabetes should aim to keep it at less than 6.5 to 7 per cent. An increase in glycosylated hemoglobin A1C reflects poor control of blood glucose.
Diabetic retinopathy may be a problem during pregnancy. Maintaining blood glucose levels within the target range is important for pregnant women with diabetes. They should work with their healthcare team to create a treatment plan that includes eating the right foods, exercise and medication. Part of this care includes having a complete, dilated eye examination as early in pregnancy as possible.
The four stages of diabetic retinopathy
This stage involves micro-aneurysms, areas where the blood vessel wall swells out to form a balloon-like pouch. Microaneurysms can affect the flow of blood through the blood vessel. At this stage vision may not be noticeably affected, but the problem becomes more severe with time if not treated.
As the disease progresses, aneurysms block all flow of blood through the blood vessel. Cells of the retina that are fed by the blood vessel do not receive nutrition and begin to die. Fluid leaving the weakened blood vessels near the macula (called macular edema) can reduce central vision.
More and more blood vessels are blocked and larger regions of the retina lose their supply of nutrients and oxygen. In response, the retina signals new blood vessels to form and feed these regions. Macular edema continues to worsen and central vision decreases.
This is the most advanced stage of the disease. New blood vessels form, but they are fragile and leaky. If the vessels begin to bleed, they can cause severe loss of vision or even blindness. They may also put traction (a pull) on the retina, so that it detaches from its supporting tissues.
In this stage, the fragile new blood vessels that grow do a poor job of nourishing the retina. Instead, they lead to other complications that can affect vision.
The vitreous is the fluid that fills the large chamber of the eye. When new blood vessels form, they can bleed into the vitreous. Sometimes they only bleed a little, so you might only see a few dark spots or floaters. When they bleed extensively, blood fills the vitreous and blocks all vision. Vitreous hemorrhage, or bleeding into the fluid at the back of the eye, can resolve on its own with time. However, any loss of vision may signal serious disease. If you experience vision loss, visit your doctor as soon as possible.
If not treated by an ophthalmologist (eye specialist), the growth of new blood vessels can be accompanied by the formation of scar tissue. Shrinking scar tissue can apply pressure to the retina and pull it off the back of the eye. If the retina detaches, you might notice new floaters or flashing lights, blank or blurred areas in your vision, or a missing section like a curtain in one eye. If left untreated, complete vision loss can result. Testing each eye by covering the opposite eye can help you to identify missing areas of your vision.
When the retina does not receive enough nutrition, it releases signals into the eye that spur new blood vessels to form. These may form on the retina or iris (the colored part of the eye).
The new blood vessels can affect circulation and create increased pressure within the eye.
Neovascular glaucoma is a serious complication of diabetic retinopathy that can damage the optic nerve and severely affect vision. In many cases, neovascular glaucoma is first recognized as a sudden loss of vision, a red, uncomfortable eye, or pain.
While there is no cure for diabetic retinopathy, treatment can slow or stop its progress for some time and prevent further loss of vision. Mild non-proliferative diabetic retinopathy may not require treatment immediately. Your ophthalmologist will regularly monitor your eyes for changes. Your family doctor and diabetic educator can assist you in ensuring that your blood glucose levels are within target range. Diet and lifestyle changes, as well as medication adjustments, will help. The final stage, proliferative diabetic retinopathy, must be surgically treated as soon as possible.
Treatment for diabetic retinopathy is highly effective. People with proliferative diabetic retinopathy have less than a five per cent chance of becoming blind within five years if they get timely and appropriate treatment.
Laser photocoagulation is a common treatment for diabetic retinopathy. An ophthalmologist uses a laser to treat areas of the retina that may produce harmful factors which cause fragile blood vessels to grow. Another treatment injects medication into the eye to reduce swelling and soak up harmful factors that lead to fragile blood vessels. For more advanced diabetic retinopathy, surgical treatments are offered. Your ophthalmologist can discuss these treatments with you.
Ask your eye care professional for advice. Many devices can help you make the most of your remaining vision and increase your quality of life. Community centres, counsellors, and occupational therapists have information about low vision counselling, training, and special services for people with vision impairments.
Shortly after being diagnosed with diabetes, you may not detect any changes in your vision. It may take time for your vision to be affected. However, harmful changes in your retina can take place without affecting your vision. With time, diabetic retinopathy will cause vision problems and can lead to blindness.
With early detection and treatment by an ophthalmologist, the risk of severe vision loss can be minimized.
It is important for you to have yearly (or more frequent) dilated eye examinations. Ensure the best possible control of your blood glucose, blood pressure, and blood cholesterol.
Take an active role in controlling your diabetes. Being responsible for your health and being attentive to changes helps prevent complications and vision loss. You can protect your vision in several ways.
At least once a year, you must have a dilated eye exam. During these examinations, drops are placed in your eyes that cause blurry vision for a short amount of time. Without these drops, a complete examination of your retina cannot be done.
Report any changes in your vision promptly to your ophthalmologist. Keeping your eyes healthy means getting the care you need as soon as you can. Be on the lookout for blurry, spotty, or hazy vision that lasts more than a few hours.
Reducing your blood pressure through medication and a healthy lifestyle can slow the progress of diabetic retinopathy.
Lowering your cholesterol can slow the progress of diabetic retinopathy. Diet, lifestyle, and medication can help you decrease your cholesterol.
Smoking can increase your blood pressure, thicken your blood, and cause blood vessels to clot. For people with diabetes, smoking is especially harmful. It also increases your risk of developing cancers, strokes, lung problems, and many other diseases.
Stress causes rapid swings in your blood glucose levels. Certain hormones, such as cortisol and adrenaline, are released under stressful conditions. These hormones can cause large increases and decreases in blood glucose levels. As well, a stressful lifestyle may not allow you to monitor your blood glucose levels as often as you should. A counsellor or support group can really help you control stress. Include meditation, massage, exercise and art in your life to reduce stress and increase your overall quality of life.
Talk to your doctor about controlling your diabetes and slowing the progress of diabetic retinopathy. Being actively involved in your health makes all the difference.