DIABETIC RETINOPATHY (DR)

Definition of diabetic retinopathy

Before defining diabetic retinopathy, here is a short explanation for diabetes and retinopathy.
Diabetes occurs when the body is not able to properly control the sugar level in blood (glycaemia). There are two different types of diabetes: Type-1, or juvenile-onset diabetes, when the body doesn’t produce enough insulin to control glycaemia and Type-2, or adult-onset diabetes, when the tissues of the body do not respond adequately to the action of insulin (insulin resistance).
Retinopathy means damage to the small blood vessels (capillaries) that irrigate the retina, a tissue located at the back of the eyes that captures the light and relies signals to the brain where they are interpreted, allowing you to see.
Diabetic retinopathy occurs when these small blood vessels are affected by the high blood sugar levels (hyperglycaemia) associated with diabetes as a complication of many years of diabetes.

There are four stages of diabetic retinopathy:

Mild non-proliferative or background retinopathy: it is the earliest stage and most common type of retinopathy. The symptoms are often mild or non-existent, and the vision is generally normal, but may be blurred in some cases. However the blood vessels in the retina have already begun to deteriorate and develop small balloon-like swellings called microaneurysms
Moderate non-proliferative retinopathy: at this stage, some of the blood vessels that irrigate the retina become blocked. The microaneurysms may begin to leak, with fluid and blood oozing into the retina
Severe non-proliferative retinopathy: as the diseases progresses, more blood vessels are blocked, hindering several areas of the retina to receive sufficient blood supply. These areas will send signals to the body for the growth of new blood vessels to compensate for the loss of blood supply. Swelling and beading of some larger retinal veins and patches of swollen nerve fibres (called cotton-wool spots because they look like fluffy wisps of cotton) may also occur. Swelling of the central part of the retina, the macula, and its diminished blood supply lead to vision problems as the macula can’t function properly, a condition called diabetic macular oedema.
Proliferative retinopathy: new tortuous blood vessels with fragile walls are growing along the retina and the surface of the jelly-like substance that fills the centre of the eye. If these vessels leak blood, it can lead to vision loss and even blindness as the blood clouds or even blocks the vision.

Frequency of diabetic retinopathy

By the end of the 20th century, estimates by the World Health Organization indicated that there are 130 million people with diabetes worldwide and that this figure will rise to 300 million by the year 2025, a 122% rise. Most diabetics will ultimately develop diabetic retinopathy, depending on the type and duration of diabetes, the quality of the control of the blood sugar level as well as of the blood pressure and blood lipid levels. Diabetes is the leading cause of blindness in patients aged 20 to 74 years.

Diabetic retinopathy is as frequent in Type-1 as in Type-2 diabetes. In Type-1, DR appears generally after 7 years of disease. After 20 years, 90-95% of Type-1 diabetics have DR out of which 40% have the proliferative stage. In Type-2 diabetics, 20% of the patients have a DR upon diagnosis of their diabetes. In the long-term these patients are more at risk for a diabetic macular oedema (60%) than for a proliferative retinopathy (20%)

In the USA, after 20 years of Type-2 diabetes, 7% of the patients are blind and it is estimated that by the year 2020, 50 million of Americans will have vision impairments.
In Japan, the incidence of background retinopathy is estimated to be 48 per 1000 persons per year and that of proliferative retinopathy to be 18 per 1000 persons per year. In South India, the prevalence of DR is 18 %. In France, it is estimated that 40% of diabetics have a form of retinopathy.

Symptoms of diabetic retinopathy

In the early stages of diabetes, the patient does usually not experience symptoms at the eye level and this is in fact quite unfortunate because retinopathy is then much easier to treat or at least to slow down its evolution. This is the reason why it is extremely important that diabetics consult regularly, at least once a year, an eye care specialist - ophthalmologist - to detect the disease at the earliest possible stage. When the disease progresses, the following symptoms may occur:

Difficulty in reading or seeing detailed work
Feeling of having cobwebs or tiny specks floating in your vision
Poor night vision
Difficulty in adjusting from bright to dim light
Dark or empty spot in the centre of your vision
Flashing lights
Blurred vision
Dark streaks or a red film that blocks vision
Sudden loss of vision in one or both eyes.

Diagnosis of diabetic retinopathy

Diabetic retinopathy is diagnosed through an eye examination. After putting some drops in your eyes to make them dilate, your ophthalmologist will check the retina for signs of the disease, such as leaking blood vessels, new blood vessels, pale fatty deposits, macular swelling or oedema and damaged optic nerve tissue. This is called a fundus examination.
The eye pressure will also be measured to detect glaucoma, which can commonly occur in diabetics.
A fluorescein angiography may also be performed, during which the ophthalmologist will inject a special dye in a vein of the arm and take photographs of the retina, to detect any leaking blood vessels.
Your doctor may request an optical coherence tomography examination. This non invasive imaging scan will show the thickness of the retina and whether fluid has leaked into the retinal tissue.

Risk factors for diabetic retinopathy

Poorly controlled blood sugar levels
High blood cholesterol levels
High blood pressure
Pregnancy.

Complications of diabetic retinopathy

Detachment of the retina due to formation of scar tissue, causing blurred vision and even complete loss of vision in severe cases
Glaucoma due to the growth of abnormal new blood vessels on the iris, the coloured area of the eye surrounding the pupil, damaging in some cases the optic nerve or even destroying the eye.

Prevention and management of diabetic retinopathy

The initial treatment involves conservative measures to prevent disease progression:

Conservative treatment

General preventive measures

Keeping blood sugar level as close as possible to normal. Tight control of blood sugar slows the onset and progression of retinopathy and lessens the requirement of medication or surgery. Discuss with your doctor about the best blood sugar levels for you and how to manage them: healthy diet, regular exercise, insulin or other anti-diabetic medication
Eye examinations should be performed every year for diabetic patients. These controls should be even more frequent in people who already have diabetic retinopathy and also in diabetic pregnant women (once per trimester)
Keeping blood pressure down to slow the progression of retinopathy. This may be achieved by lifestyle changes and anti-hypertensive medications
Controlling your cholesterol by lifestyle changes and lipid-lowering medication
Stop smoking as smoking promotes the closure of blood vessels.

Therapeutic measures

Oral treatment with vessel protective drugs of synthetic origin slows down and stabilizes disease progression by reducing in particular swellings, leakages and bleeding in the retina. It may postpone the need for subsequent laser surgery
Local injections in the eye are under study with different products.

Interventional treatment

Laser surgery - or laser coagulation or photocoagulation - is applied in severe macular oedema and proliferative retinopathy to slow down progression of vision loss. During this painless procedure, a laser beam is aimed through the eye to seal off leaking blood vessels and destroy new abnormal vessels. Some loss of side vision may occur as well as change in colour and night vision. It should, however, be stated that once retinopathy has reached the proliferative stage, it is difficult to reverse.
Vitrectomy may be used in subjects with proliferative retinopathy having had extensive bleeding from damaged blood vessels in order to remove the blood from the gel-like area called vitreous humour. During this procedure, generally done under local anaesthesia, the doctor makes a small incision in the white part of the eye, removes the cloudy vitreous humour and replaces it with a salt solution to maintain the normal shape and pressure of the eye. The vitreous humour is gradually replaced and vision improves

Any medical information on this website is not intended as a substitute for informed medical advice. No action should be taken before consulting with a healthcare professional.