Diabetes affects the entire body. Body cells require glucose to survive. Normally, the amount of glucose (sugar) in the blood is tightly controlled. However, too much or too little glucose in the blood can disturb how the body’s 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 signals the body cells to take up glucose from the blood. Insulin’s job is to remove glucose from the blood to prevent damage to the organs.
Diabetes damages the blood vessels that nourish the retina. The retina is a sensory layer of the eye. It changes images passing through the eye’s lens into electric signals. These signals are sent through the optic nerve to the brain.
One part of the 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 the retina for specialized vision.
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 cannot do their job well. When this happens, your sight can be affected.
When diabetes is poorly controlled, the blood vessels feeding the retina can become leaky. Fluid can seep into the retina (and macula), causing it to swell. Swelling in the macula disturbs central vision. Since the retina is not getting enough nutrition, abnormal blood vessels begin to form. These new blood vessels are fragile and can bleed inside the eye, causing floaters and vision loss.
This stage involves microaneurysms. In these areas, 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. The cells of the retina that are fed by the blood vessel do not receive nutrition and begin to die. In macular edema, fluid leaves the weakened blood vessels near the macula and seeps into the macula. This reduces central vision.
As more and more blood vessels are blocked, larger regions of the retina lose their supply of nutrients and oxygen. More bleeding can be seen in the retina. Patches of retina without enough blood begin to die and appear as white fluffy areas called ‘cotton wool spots.’ Macular edema continues to worsen and central vision reduces.
This is the most advanced stage of the disease. Large areas of the retina are not getting enough blood, and new abnormal blood vessels form. These new vessels 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 (tension) on the retina, causing it to tear and detach (pull off) from the back of the eye.
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 see a few dark spots or floaters. When they bleed a large amount into the vitreous fluid, the blood blocks all vision. A vitreous hemorrhage 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), these new emerging blood vessels can create scar tissue. When the scar tissue shrinks, it can apply pressure to the retina and pull it off the back of the eye. If the retina detaches, you might notice:
Left untreated, complete vision loss can occur. Testing each eye by covering the opposite eye can help you to identify missing areas of your vision.
Fluid is produced by the eye and drains near the iris (the coloured part of the eye). In proliferative diabetic retinopathy, abnormal blood vessels growing on the iris block fluid from draining. As a result, the pressure inside the eye can increase. It can damage the optic nerve and severely affect vision. This condition, called neovascular glaucoma, is a serious complication of diabetic retinopathy.
While there is no cure for diabetic retinopathy, it is preventable. Your diabetes care team can help you to manage your blood glucose so that your levels stay within target range. Lifestyle changes can help you improve control. Eat a balanced diet, paying careful attention to the sugar content and glycemic index of foods. Regular exercise helps maintain a healthy blood glucose level. Quit smoking and manage blood pressure to prevent additional complications from diabetes like heart attack and stroke.
Diabetes medications or insulin are often needed to help control blood glucose levels, and must be used as prescribed.
If you have diabetic retinopathy, regular eye examinations by an ophthalmologist are necessary. Monitoring the health of your eyes assesses whether treatment is required. Ophthalmologists can offer treatments for diabetic retinopathy which prevent further loss of vision.
Mild, non-proliferative diabetic retinopathy may not require treatment immediately. Your ophthalmologist will regularly monitor your eyes for changes. If swelling is found in the retina and macula, or when new blood vessels begin to form in the retina, act quickly. Without rapid treatment, you may lose your vision.
Treatment for diabetic retinopathy is highly effective. With timely and appropriate treatment, those with proliferative diabetic retinopathy have less than a five per cent chance of becoming blind within five years.
Injections of medications inside the eye can treat swelling of the retina and prevent abnormal blood vessels from growing. Your ophthalmologist will discuss the different medications that are being used. Some people only need an injection once every few months, while others require more frequent injections. Only a specialist should perform injections into the eye. Ask about the risks and benefits of these procedures.
Laser photocoagulation is a common treatment for diabetic retinopathy. An ophthalmologist uses a laser to reduce swelling of the retina or reduce the growth of abnormal blood vessels. Again, these procedures should only be done by a specialist.
With more advanced diabetic retinopathy, such as bleeding inside the eye or detached retina, surgical treatments are offered. Many people, including those with diabetes, require surgery to remove the cataracts which develop with aging. Neovascular glaucoma may also require treatment with eye drops, injections inside the eye, laser treatment, or surgery. Your ophthalmologist can discuss these treatments.
In expecting mothers with diabetes, diabetic retinopathy may get worse during the pregnancy. Maintaining blood glucose levels within target range is important. Regular eye examinations are also needed to monitor the health of your retinas and prevent vision loss. If you have diabetes, ask your care team about how diet, lifestyle, and medication use can support your pregnancy.
Talk to your eye care professional. Ask about the major causes of your vision loss, and whether any therapies or surgeries might improve your vision. A wide variety of tools and devices can help to make the most of remaining vision and increase quality of life. Community health centres, counsellors, Canadian Diabetes Association (www.diabetes.ca) and occupational therapists have information about low vision counselling, training, and special services for people with vision impairments.
How will changes in my vision progress?
When you are first diagnosed with diabetes, you may not have noticed any changes to your vision. Diabetic retinopathy may be seen right away, or can take years to develop. You may not know that you have this complication. Your vision may seem normal, even though harmful changes are taking place in the retina. Regular eye examinations by an ophthalmologist can identify diabetic retinopathy and reduce the risk of vision loss.
Your doctor can use an A1C test to find out how well you are controlling your blood glucose levels. It requires 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.
If you have diabetes, discuss your target HbA1C level with your doctor.
Take an active role in controlling your diabetes. Being responsible for your health and attentive to changes helps prevent complications and vision loss. Protect your vision in the following ways.
Report any changes in your vision to your ophthalmologist right away. Get the care you need promptly, as it is a critical part of keeping your eyes healthy. Be on the lookout for blurry or hazy vision that lasts more than a few hours. If you notice sudden floaters (black spots in your vision), contact your ophthalmologist.
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.