Diabetic retinopathy

Diabetic retinopathy is a complication of diabetes that causes damage to the blood vessels in the retina. Diabetic retinopathy is the most common cause of irreversible blindness in the working population in the Western world. Diabetic retinopathy occurs in more than half of people who develop diabetes.

Symptoms

It is possible to have diabetic retinopathy for a long time without noticing symptoms until significant damage occurs. Symptoms of diabetic retinopathy may occur in one or both eyes.

Symptoms can include

• Blurry vision
• Difficulty reading
• The appearance of spots - commonly called "floaters".
• Shadowing of vision
• Eye pain or pressure
• Difficulty in color vision

Causes

The main cause of diabetic retinopathy is diabetes – a condition in which blood glucose (sugar) levels are too high. The elevated sugar levels from diabetes can damage the small blood vessels that feed the retina and can in some cases block them completely.

When damaged blood vessels leak fluid into the retina, a condition known as diabetic macular edema occurs, which causes swelling in the central part of the retina (macula) that provides the clear vision needed for reading and recognizing faces.

Prolonged damage to the small blood vessels of the retina leads to poor circulation in the retina and macula, causing the development of growth factors that cause the growth of new abnormal blood vessels (neovascularization) and scarring on the surface of the retina. This stage of the disease is known as proliferativediabetic retinopathy (PDR).

The new vessels can bleed inside the eye, cause scar tissue to form, pull on the retina, cause retinal detachment, or cause high pressure and pain if the blood vessels grow in the iris, blocking the eye's drainage system. This can cause vision loss.

Risk factors

Anyone with diabetes is at risk of developing diabetic retinopathy. Additional factors can increase the risk:

• Duration of disease: the longer someone has had diabetes, the greater the risk of developing diabetic retinopathy.
• Bad control of blood sugar levels 
• High blood pressure
• High cholesterol levels
• Pregnancy

Diagnosis

The best way to diagnose diabetic retinopathy is with an eye exam. During this exam, the doctor puts drops in your eyes to dilate your pupils. 

The doctor will look for:

• Swelling in the retina that threatens vision (diabetic macular edema)
• Evidence for poor blood circulation in the retina 
• Abnormal blood vessels that may predict an increased risk of new blood vessels developing
• New blood vessels or scar tissue on the surface of the retina 

Regular eye exams are important, especially for those at higher risk for diabetic retinopathy. If you're over 50, an exam every 1 to 2 years is a good idea so your doctor can look for signs of diabetes or diabetic retinopathy before any vision loss occurs.

In addition to checking for signs of diabetic eye disease, a comprehensive eye exam will evaluate your vision/need for corrective lenses, eye pressure, lens, as well as a complete examination of the retina and vitreous.

In addition to this test, doctors use other tests to detect and manage diabetic retinopathy:

Optical coherence tomography (OCT) provides highly detailed cross-sectional images of the retina that show its thickness, helping to determine whether fluid has leaked into the retinal tissue.

The doctor may take pictures of the retina to help detect and document diabetic retinopathy. These pictures make it easier for the doctor to monitor the disease at follow-up visits to see if it is getting worse.

To assess retinal blood vessel circulation, the doctor may perform a test called fluorescein angiography (FA). In this, the doctor will inject a dye into a vein in the patient's arm. The dye then circulates through the eyes and acts as a contrast agent. However, it does not affect the kidneys and is not related to the dye used with CT and MRI scans.

As the dye circulates, the doctor takes images of the retina to accurately detect blood vessels that are blocked, damaged, or leaking fluid. 

Treatment and outcome

There are many approved treatments for diabetic retinopathy, including intravitreal injections, laser treatments, and vitreous and retinal surgery. 

Research has shown that eye injections often lead to better vision than laser treatment alone for patients with diabetic macular edema. The key to these treatments is their ability to block vascular endothelial growth factor (VEGF), a substance that stimulates the leakage and abnormal growth of blood vessels. Repeated doses of anti-VEGF drugs may be needed to prevent fluid from leaking from the blood vessels and vision loss.

Prevention

Patients with diabetes often ask, “Is there anything I can do to keep from getting diabetic retinopathy or to prevent or treat vision loss once it occurs?”

If you have diabetes, it is important to stay in good physical shape.

• Take your medications as directed by your doctor.
• Watch and maintain a healthy weight
• Add physical activity to your day
• Check your blood pressure and cholesterol
• Stop smoking
• Regular eye exams reduce the risk of developing more serious complications from the disease.

It is extremely important for diabetic patients to maintain the eye examination schedule prescribed by their retina specialist. How often an examination is needed depends on the severity of your disease. Through early detection, your retina specialist can initiate treatment to prevent vision loss in almost all patients and preserve the activities you enjoy most.