Ravi (name changed), aged around 40, visited a local doctor when he experienced a loss of vision. The doctor diagnosed him with diabetes, and diabetic retinopathy (DR), a disorder in which diabetes causes damage to the retina of the eye. Ravi had never known that he had diabetes, but the DR had advanced to an extent where he had already lost 50% of his vision. He had to undergo surgery soon after.

Dr Dhanashree Ratra, Senior Consultant at the Department of Vitreo Retinal Diseases, Sankara Nethralaya, who had treated Ravi, says, “He underwent aggressive treatment with us, and now his vision is nearly normal.”

Not all are as fortunate as Ravi; many patients with Diabetic Retinopathy become completely blind or suffer major vision impairment. DR causes a huge proportion of avoidable, irreversible blindness, according to doctors. “The leading cause of blindness in India is cataract. But cataract-related blindness can be reversed by replacing the lens in the eye. But in DR, after a certain stage, vision loss cannot be reversed,” says Dr Dhanashree.

DR also does not show symptoms in the early stages, which means many – including those diagnosed with diabetes – are unaware that they even have it.

“In the Retina Department – which is a tertiary care department – of major hospitals like Aravind and Sankara Nethralaya, about 70% of OPD patients are those suffering from DR. And out of all DR patients, 30-40% have irreversible vision loss,” says Dr Anand Rajendran who heads the Vitreo-Retinal Service at Aravind Eye Hospital, Chennai.

According to Dr Rajendran, the number of cases has been increasing, especially in urban areas. A largely carbohydrate-based diet, especially in South India, and an increasingly sedentary lifestyle are contributing to this. “In any case of DR, vision will be affected to some extent. Hundred percent normalcy may not be possible,” he says.

Studies say that DR could potentially be an epidemic in India in future, given the increasing number of diabetics, especially in urban areas. The Diabetes Atlas, 2015, published by the International Diabetes Federation said that 8.7% Indians – around seven crore people – were diabetic. Many diabetes cases are undiagnosed too. The number is expected to go up to 12 crore by 2040.

Diabetes in urban areas is far higher than that of rural areas, as per the ICMR-INDIAB study of 2011 in four states – Jharkhand, Tamil Nadu, Maharashtra and Chandigarh. In Jharkhand, prevalence of diabetes in urban areas (13.5%) was more than four times higher than in rural areas (3%). In the other three states, urban areas had nearly twice the rate of incidence compared to rural areas.

What is DR?

Diabetes mainly affects the retina of the eye, a layer of tissue in the eye that senses light and sends visual impulses to the brain. The disease can cause blood vessels in the retina to be obstructed, restricting blood supply to the retina.

In DR, vision loss can be caused by macular edema, haemorrhage or retinal detachment, explains Dr Rajendran. In macular edema, the macula or the central part of the retina is affected by fluid leakage. In cases of haemorrhage, the retina is damaged by blood leaking from new, weak-walled blood vessels that are formed as the disease progresses to an advanced stage. In some cases there will be fibrosis or scar tissue formation, which can even cause the retina to detach. Haemorrhage and retinal detachment are more likely to cause vision loss than macular edema, says Dr Rajendran.

He narrates the recent case of a man in his 60s, who had been suffering from diabetes for long. “He was unable to control his blood sugar levels. When he came to us, his vision was almost entirely gone. New blood vessels had formed on the retina, leading to retinal detachment; as a result, he had developed glaucoma too. His blindness cannot be reversed; he was only given eye drops to reduce the pressure inside the eye,” says Dr Rajendran.

About a fifth of diabetics affected

Dr Dhanashree says that 18-20% of diabetics get DR. A 2009 study, conducted by Sankara Nethralaya among around 5800 Chennai residents aged above 40, had found that 18% of diabetics had DR. This was in close alignment with the findings of CURES, the Chennai Urban Rural Epidemiology Study of 2005, conducted among 26000 people, which found that 17.6% of diabetics had DR.

A 2014 national-level largely-urban study, held by the All India Ophthalmological Society showed that 21.7% of diabetics had DR. It also showed huge variations across different parts of the country. DR was highest among diabetics in North India, at 34%. In the east, west and southern parts of India, the rates hovered around 22%. But in northeast and central India, the rates were as low as 14% and 12% respectively.

The study suggests that these differences could be because of variations in health care access in different regions. However, studies have shown that DR rates among Indians overall, are far lower than that of western countries.

Studies also show that DR has the strongest correlation with the number of years a person has had diabetes, and varies inversely with the extent of blood sugar control. CURES had found that the risk for DR increased 1.89 times for every five years the person has had diabetes.

“There are patients who have had diabetes for decades, but still do not have DR because they control their blood sugar levels well. So it varies from one patient to the other. Other issues such as high blood pressure, kidney-related diseases also increase the chance of DR. So the patient has to control those too,” says Dr Dhanashree. She says that people with Type I diabetes have a higher risk of DR than those with Type 2 diabetes.

Preventing and managing DR

Since DR does not show symptoms in the early stages, doctors say that annual eye checkups are a must as soon as one is diagnosed with diabetes. A 2014 national survey among urban diabetics shows why. The survey found that about half of them already had some degree of vision loss by the time they went to an eye care facility, even though they were unaware of the onset of DR.

“Once a patient is diagnosed with DR, checkups are done more often. In the earlier stages, no treatment or medication is administered. We only observe the patients, and they have to control their sugar levels,” says Dr Dhanashree.

In the advanced stages, patients may see dark spots, lose vision to the extent that they can see only hand movements etc. Treatments like surgery, laser and anti-VEGF injections are available then. After treatment, regular follow-up and monitoring is needed.

“DR is like fracture; if treated early, the patient has a higher chance of getting back normal vision. Else, it is difficult to treat,” says Dr Rajendran.

Thus with some care, diabetics can prevent or manage DR and avoid vision loss; awareness is of paramount importance.