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Diabetic Retinopathy - a threat to your vision

Diabetic Retinopathy (D.R.) is the major cause of preventable blindness in the working age group. D.R. is fast emerging as a public health problem in the developing parts of the world. WHO has predicted that in 20 years, India will have more diabetic people than any other country. The present diabetic population in India is around 21 million which would go up to 57.2 million by 2025. The prevalence of diabetic retinopathy is strongly related to the duration of diabetes. It is noteworthy that the diabetics live longer due to better treatment facilities available for them.

The aim of screening is to identify DR at an early stage and to treat with time tested efficacious modalities such as laser photocoagulation thereby preventing sight threatening complications.

Eye, Retina & DR
Risk factors for DR
Background DR
Proliferative DR (PDR)
Symptoms of DR
Timing of the first eye examination
Diagnosis of DR
Complications of Diabetic Retinopathy
Management of DR
Lasers in DR
Surgery in DR

Eye, Retina & DR
Eye is like a camera and the retina like a film in a camera. It is the seeing tissue of the eye. Retina has two parts: the peripheral retina and the central part known as macula. In DR, the blood vessels of the retina become abnormal and cause the problems that diabetic patients have with their eyesight.

Risk factors for DR
The most important is the duration of diabetes. The other risk factors being - type of diabetes, hypertension, pregnancy, high cholesterol and triglyceride levels and diabetic nephropathy.

Background DR
Normally, the blood vessels in the retina do not leak. But with diabetes, the retinal blood vessels develop tiny leaks. These leaks cause fluid or blood to seep into the retina. The retina then becomes wet and swollen, causing diminution of vision. This is known as background or Non-proliferative Diabetic Retinopathy (BDR or NPDR).

Proliferative DR (PDR)
Retina depends on the blood vessels for its nutrition. Diabetes can cause closer of blood vessels and the areas of the retina in which the blood vessels have closed then foster the growth of abnormal new blood vessels which are very fragile and can cause bleeding and traction on the retina leading to retinal detachment and total loss of vision. This form of DR in which abnormal new blood vessels grow (or proliferate) is called proliferative DR.

Symptoms of DR
The most important thing to remember is that DR often has no early warning signals. Even in advanced cases, it may progress a long way without any symptoms. Hence, regular eye examinations for all the diabetics are a must.

Other symptoms could be gradual progressive diminution of vision, sudden loss of vision, difficulty in reading, seeing floaters in front of the eye.

Timing of the first eye examination
In diabetics aged less than 30 years - 5 years after the diagnosis of diabetes.

In diabetics aged more than 30 years - at the time of diagnosis of diabetes.

Frequency of the follow-ups depends on the clinical findings.

Diabetic retinopathy becomes worse during pregnancy therefore eye examination should be done before conception and every three months during pregnancy.

Diagnosis of DR
Complete eye examination including the check up of the retina after dilating the pupils with drops. Sometimes a specific test called Fluorescein Angiography maybe done including the injection of a dye through a vein and taking photographs of the retina through a special camera.

Complications of Diabetic Retinopathy
Bleeding from the new blood vessels causing hemorrhage in the eye cavity known as vitreous hemorrhage.

Growth of the scar tissue on the retina that can pull the retina off the back wall of the eye-called tractional retinal detachment. Sometimes holes can develop in the retina due to the scar tissue pulling on it causing rhegmatogenous retinal detachment.

Abnormal blood vessels can grow on the iris, the colored part of the eye-called rubeosis. This can close the normal flow of fluid out of the eye causing the pressure in the eye to rise. This condition is known as neo-vascular glaucoma and can cause pain and permanent loss of vision.

Management of DR
The key to the management of DR is the early diagnosis and timely treatment with regular follow -up.

Lasers in DR
Laser treatment can be very helpful in limiting the damage caused by DR. The laser beam is a high energy light that turns to heat when it is focused on the parts of the retina to be treated.

In background DR, the laser heat either seals or reduces the leakage of fluid from the blood vessels and allows the macula to dry.

In proliferative DR, the laser destroys the diseased portions of the retina to stop the growth of new blood vessels. In cases of vitreous haemohrage, the laser cannot make the blood to disappear, but it can prevent more bleeding.

Surgery in DR
An operation known as vitrectomy is done in cases of PDR with non-clearing vitreous hemorrhage or retinal detachment.

What is important to remember is that once retinopathy starts, even the control of blood sugar will not stop it. This makes it vital for people to have an eye examination once a year and not just when their sugar is high but even when it has been controlled.

In the recent past, there has been a significant progress in understanding the pathogenesis of DR. Various factors involved in the progression of DR such as protein kinase CB(PKC B),VEGF and other have been identified. The future beholds a new paradigm results from pharmaceutical compounds which target key molecules to inhibit the hyperglycemia induced pathways.

The author, Dr. Manisha Agarwal, is a retinal consultant with Dr Shroff's Charity Eye Hospital.

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