Diabetic Retinopathy

Diabetic retinopathy is a complication of diabetes mellitus and is one of the main causes of blindness in young and middle-aged adults today. The incidence of diabetes mellitus is on the rise world over, in India more than 60 million people are suffering from it. It occurs when diabetes damages the tiny blood vessels inside the retina, the light-sensitive tissue at the back of the eye. A healthy retina is necessary for good vision.

Diabetic retinopathy often has no early warning signs. But over time, it can get worse and cause vision loss. Diabetic retinopathy usually affects both eyes.

What are the types of diabetic retinopathy?

Diabetes affects the peripheral and central retina in different ways. The peripheral retina can be affected by non-proliferative and proliferative diabetic retinopathy.

Non-proliferative diabetic retinopathy, also known as background diabetic retinopathy, is the early stage of diabetic retinopathy and occurs when the small retina blood vessels become affected and begin to leak and bleed. At this stage, vision is usually not affected.

Proliferative diabetic retinopathy is an advanced stage of diabetic retinopathy associated with a high risk of permanent loss of vision. There is growth of abnormal new blood vessels in the retina. These abnormal new vessels can rupture, causing significant bleeding that will lead to loss of vision. Progressively, scar tissues form and cause retinal detachment. The abnormal blood vessels can grow on the iris and block fluid outflow from the eye causing neovascular glaucoma which leads to a risk of optic nerve damage and blindness.

The central retina can be affected by diabetic macular oedema in both non-proliferative and proliferative diabetic retinopathy. Vessels in the centre of the retina leak fluid causing retinal swelling and loss of central vision.

What are the symptoms of diabetic retinopathy?

Floaters perceived by patients in diabetic retinopathy

Diabetic retinopathy has no warning signs in the early stages; sight may not be affected until the condition is severe. As the disease progresses, symptoms may include the loss of central vision when reading or driving, loss of the ability to see colour, and mild blurring vision.

Small spots or floaters may also indicate blood vessel leaks and may clear up in days, weeks, or even months. In the most severe form, with proliferative diabetic retinopathy, there may be sudden severe vision loss from vitreous bleeding or tractional retinal detachment.

Any person with diabetes can develop retinopathy. Because the disease is initially showing no symptoms and can be treated in the earlier stages, it is important to have a regular dilated eye examination each year, and immediately if you experience any of these symptoms. Late diagnosis and treatment can result in irreversible vision loss.

How to prevent diabetic retinopathy?

Fundus Photography

You cannot completely prevent diabetic retinopathy. However, vision loss can be prevented with early detection.

You can also help slow down the development of diabetic retinopathy by keeping your blood glucose in check. The HbA1c is a measure of blood sugar level over a three-month period and it should ideally be less than 7 per cent. Control of high blood pressure is also key in preventing the development and progression of diabetic retinopathy.

Other medical conditions such as high cholesterol, kidney disease and heart disease should be treated and kept under control. Stop smoking and exercise regularly to reduce your risk of developing diabetic retinopathy.

Who is at risk of developing diabetic retinopathy?

All diabetics are at risk of developing diabetic retinopathy. This is especially so if diabetes is long-standing. After 20 years, most diabetics will develop this complication to some degree. Those who have poorly controlled diabetes are at higher risk of developing diabetic retinopathy earlier and at more severe stages.

People with diabetes should get a comprehensive dilated eye examination or screening at least once a year. If you have diabetic retinopathy, your ophthalmologist can recommend treatment to help prevent its progression.

Young diabetics (type 1 disease) are at a higher risk of developing advanced retinopathy changes and are susceptible to faster progression of the disease.

How to diagnose a case of diabetic retinopathy?

Dilated eye exam using Indirect Ophthalmoscope

Diabetic retinopathy is diagnosed with a dilated eye examination by your ophthalmologist. In addition, the tools required to provide comprehensive diabetic retinopathy management are:

Fundus photography can provide an effective and efficient assessment of the diabetic retinopathy status in most patients, although those with media opacity like significant cataract may not be suitable.

Optical Coherence Tomography (OCT) helps in ascertaining the presence of macular edema as well as in follow-up on treatment for the same.

Fluorescein Angiography (FA) aids in identifying the leaky blood vessels and the perfusion status of the macula.

Treatment Options

In most cases, laser therapy can prevent significant vision loss associated with diabetic retinopathy.

A procedure called laser photocoagulation can be performed to seal or destroy growing or leaking blood vessels in the retina.

• Panretinal photocoagulation (PRP)This is used to treat the peripheral retina to prevent or stop the growth of the abnormal new blood vessels.
• Focal laserThis is used to treat macular edema to reduce swelling.

Laser photocoagulation treatment

In general, each eye requires two to three sessions for a PRP to be completed. You will be expected to go for regular treatments over a period of six to twelve months before diabetic retinopathy is controlled adequately. Laser photocoagulation in diabetic retinopathy hence stabilizes the disease process and prevents vision loss in these patients.

In patients with loss of central vision due to diabetic macular oedema, intravitreal injections of medicines into the centre of the eye can reduce the macular swelling and improve vision.

Medications injected into the eye for diabetic macular oedema include Anti-Vascular Endothelial Growth Factor (VEGF) drugs such as Avastin, Accentrix and Eylea, as well as steroids (Ozurdex).

Often, multiple injections at intervals of one month or longer are required to resolve the swelling. Repeated injections at longer intervals may also be required to maintain visual improvement.

In some people with diabetic retinopathy, the abnormal blood vessels in the retina may also result in massive bleeding into the centre of the eye (vitreous haemorrhage), causing sudden severe loss of vision.

A surgical procedure called vitrectomy can be used to remove blood that has leaked into this part of the eye. Vitrectomy may also be required if there is a tractional retinal detachment, but this marks the end stage of the disease that may be prevented with early laser treatment.