The disease may progress a long way without symptoms; hence regular eye examinations are vital for diabetics

Diabetes is one of the fastest growing diseases in India. According to the World Health Organisation, India is expected to become one of the major hubs of diabetic population during the next two decades. The number of adult-onset diabetes mellitus cases is expected to witness a staggering 266 per cent increase — from 18 million in 1995 to 80 million in 2030.

The prevalence of diabetes in the general population is also on the increase. It is estimated to be around 28 per cent in the urban population and five per cent in the rural population. Of these diabetic patients, about 18 per cent develop diabetic retinopathy.

Some hard-hitting facts about diabetes are that:

*A third of people with diabetes never know that they have diabetes; just a two-thirds of diabetics go for medical attention;

*Among the population of diabetics, only a miniscule percentage is referred for regular eye check-ups.

* Not all ophthalmologists in India are trained to detect and treat diabetes related retinal disease: diabetic retinopathy.

*Diabetic retinopathy is an important cause of blindness in the working age group.

*A diabetes patient is 25 times more likely to go blind than a person without diabetes.

*Diabetes is a serious disorder that can cause blindness, heart disease, kidney failure and amputations.

*Taking good care of yourself through diet, exercise and special medications, you can control diabetes.

And the good news is that, diabetes related visual loss due to diabetic retinopathy can be treated even before the visual loss occurs.

Diabetes and the eye

The eye functions much like a camera. In a normal eye, light enters through the front part of the eye, the cornea and gets focussed by the lens onto the retina, the light sensitive screen at the back of the eye. The retina changes the light into nerve signals and sends these signals along the optic nerve to the brain. Without a retina, the eye cannot communicate with the brain, making vision impossible.

Diabetic eye diseases refer to a group of eye problems that people with diabetes may develop as a complication of this disease. If left untreated, the vision problems can lead to severe vision loss or even blindness. Diabetic eye diseases include — cataract - clouding of the eye's lens; glaucoma - increase in the fluid pressure inside the eye that leads to the optic nerve being damaged and loss of vision and diabetic retinopathy - damage to the blood vessels in the retina.

In addition, diabetes can also affect the optic nerve and cause Anterior Ischemic Optic Neuropathy (AION) and palsies of the nerves that supply to the external muscles of the eye.

So what then is diabetic retinopathy and how does it damage the retina?

The retina gets its food supply from various blood vessels that are present in the retina. Normally, the retinal blood vessels do not leak. But in patients with diabetes, the retinal blood vessels can develop tiny leaks, which cause fluid or blood to seep into the retina; the retina becomes wet and swollen and cannot work properly. This is known as diabetic retinopathy.

The central part of the retina is known as macula, and it is the most important and sensitive area for us to see and read. In patients with diabetic retinopathy, if the damaged blood vessels leak fluid and lipids onto the macula, it results in a condition known as diabetic maculopathy an important reason for the blurring of vision in diabetes patients.

Another problem with the retinal blood vessels in diabetics is that they may get blocked. The retinal tissue, which depends on these vessels for nutrition, will no longer work properly. Further, this area then fosters the growth of abnormal new blood vessels; these new fragile new blood vessels grow along the retina and in the clear, gel-like vitreous that fills the inside of the eyes. This advanced stage of diabetic retinopathy is known as proliferative diabetic retinopathy. Without timely treatment, these new blood vessels can bleed, cloud vision and destroy the retina.

Symptoms

Diabetic retinopathy often has no early warning signals. Vision may not change until the disease becomes severe, nor is there any pain. Blurred vision may occur when the macula, the central part that provides the sharp vision, swells from the leaking fluid. Blurred vision makes it hard to do things like read and drive.

As the new blood vessels bleed, you may notice a few specks of dark spots or clouds, floating in your vision. Sometimes bleeding inside the eye might be of severe nature, blocking complete vision — this often happens during the sleep.

Remember that even in advanced cases, the disease may progress a long way without symptoms; hence, regular eye examinations for people with diabetes are so important.

To detect diabetic retinopathy, a patient is subjected to a series of eye examinations including visual acuity test, pupil dilation, ophthalmoscopy and Fluorescein angiography.

Treatment

There are two treatments for diabetic retinopathy which are very effective in reducing the loss of vision. In fact, even people with advanced retinopathy have a 90 per cent chance of retaining vision provided they get treatment before the retina is severely damaged.

These two treatments are laser surgery and vitreous surgery. It is important to remember that though both these treatments are successful, they do not cure diabetic retinopathy. One would wonder why undergo treatment if it does not cure the disease?

Treatments are successful in stopping the leak or destroying the new vessels and to prevent further damage to the retina. Damage done cannot be undone. Patients who develop very advanced stage of diabetic retinopathy are prone to retinal detachment.

Possible complications

As with all surgery, there are risks associated with surgery for diabetic eye conditions. Complications are unusual, but can include cataract, increased pressure in the eye — glaucoma, bleeding, retinal detachment, infection and loss of vision.

Remember if proliferative diabetic retinopathy remains untreated, about half of those who have it become blind within five years, compared to just five per cent of those who receive treatment.

Can it be prevented?

Not totally, but your risk can be greatly reduced. Several factors that might help in delaying the onset and progression of diabetic retinopathy and preservation of vision include:

*Good control of blood sugar

*Avoiding smoking

*Maintaining a healthy diet

*If diabetes is diagnosed before the age of 30, please have an eye examination within five years of diagnosis.

*If the diabetes is diagnosed after the age of 30, please have an eye examination as soon as the diagnosis of diabetes is confirmed

*If a pregnant woman is diabetic, please have an eye examination within the first three month so of pregnancy.

*Most important factor for the development of diabetic retinopathy is the duration of diabetes.

Who is at risk?

All people with diabetes are at risk; during pregnancy, diabetic retinopathy may worsen. The longer a person has diabetes, the greater the risk of developing diabetic retinopathy. Nearly half of all the people with diabetes will develop some degree of diabetic retinopathy during their lifetime.

(The writer is Senior Consultant, Shri Bhagwan Mahavir Vitreoretinal Services, Sankara Nethralaya, Chennai. His email id is rajivpgraman@gmail.com)