How does diabetes affect the eyes?
Diabetes is a chronic disease in which your blood glucose or sugar levels are very high. Uncontrolled levels pose risk to the heart and brain as well as the legs based on large vessel disease, but just as important the eye, kidney, and nerves can be damaged by small vessel disease.
People with diabetes may develop three major eye problems – glaucoma, cataract, and retinopathy. The early symptom of all these disorders is blurred vision. High blood sugar causes swelling of the lens in the eye, distorting the ability to focus clearly. Retinopathy is the most common eye disease associated with diabetes, and is one of the leading causes of blindness in adults.
What is diabetic retinopathy?
Diabetic retinopathy is a disease which damages the tiny blood vessels in the retina (the light-sensitive tissue at the back of the eye). Having diabetes for a long time increases the chances of developing diabetic retinopathy.
Types of diabetic retinopathy
There are three main types of retinopathy in diabetes, including:
- Background retinopathy: blood vessels are damaged, but vision is not affected.
- Maculopathy: the macula (centre of the retina) is damaged. This significantly reduces your vision.
- Proliferative retinopathy: new blood vessels may grow from damaged blood vessels when the eye is deprived of oxygen. These new vessels are fragile and can bleed easily.
Risk factors for diabetic retinopathy
You chances of developing diabetic retinopathy increase with the following factors:
- Long duration and poor control of diabetes
- High cholesterol
- High blood pressure
Complications of diabetic retinopathy
High levels of sugar in your blood from diabetes can cause damage to the blood vessels supplying the retina and loss of sight when the vessels become blocked and blood supply is cut off. In response, the eye grows new vessels, but these do not develop properly, and can leak and cause vision loss. Scar tissue can also form, pulling the retina and causing it to detach.
Symptoms of diabetic retinopathy
The early stages of the disease do not show any symptoms; but as the condition worsens you may have blurred vision, spots or dark shapes floating in your vision (floaters), reduced night vision, or temporary or permanent blindness.
Diagnosis of diabetic retinopathy
Your doctor will diagnose diabetic retinopathy using the following methods:
- Dilated eye exam is a good diagnostic tool for retinopathy. Drops will be placed in your eye to dilate your pupils (the black of your eye). This will help your doctor look for the presence of cataract, abnormal or new blood vessels, swelling, blood or fat deposits in the retina, scar tissue and retinal detachment.
- Tests for vision and eye pressure may be performed.
- Fluorescein angiography may be performed, in which a special dye is injected into your arm and images of the blood vessels are taken as the dye circulates into the eye. This will show the blood vessels that are broken, leaking or blocked.
- OPTOS photography is critical in assessing the entire retina and is a more comfortable examination compared to the bright light assessment with indirect ophthalmoscopy. OPTOS photography also serves as a reference to the state of the disease and can be used in follow up.
- Optical coherence tomography takes sectional images of the retina to determine leakage into the retinal tissue. Optical Coherence tomography is also known as OCT.
Diagnosis is critical, as if it is not detected and treated early, diabetic retinopathy can eventually lead to blindness.
Treatment of diabetic retinopathy
Treatment is decided based on the type and severity of the disease, and your response to prior treatment. Nonproliferative diabetic retinopathy may not require immediate treatment. Maintenance and control of blood sugar levels can prevent progression to more serious stages of retinopathy. However, severe cases may require surgery. The procedures include:
- Focal laser treatment: A laser is used to burn abnormal vessels to stop or slow down blood leakage. Focal laser treatment for macular disease is being used less and less but does stop lipid leakage.
- Anti-VEGF therapy is an injection of drugs that block growth factors are used to minimize swelling such as oedema and reduce active new vessels. These injections are usually given every month until the disease subsides.
- Scatter laser treatment: A laser is used to burn, shrink and scar abnormal vessels.
- Vitrectomy: Scar tissues pulling the retina and blood leakage are removed and replaced with a salt solution to maintain the shape of the eye.
- Lipidil, a drug which is known to reduce damage to the macula when there is lipid leakage within the macular region.
Treatment can slow down the progression of the disease, but is not a cure as the underlying cause, diabetes, is a lifelong condition. Regular monitoring of the condition of the eye is important and additional treatment may be required.