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Diabetic retinopathy: Reducing the risks
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The control of diabetes, blood pressure, and anaemia is important in halting the progression of diabetic retinopathy. Dr. TARUN SHARMA looks at a preventable form of blindness.
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Diabetes can affect several members of a family.
DIABETES is one of the fastest growing diseases in India. In 1995, throughout the world, nearly 135 million people had diabetes; however, the World Health Organisation (WHO) has estimated that in India, the number of adults with diabetes would be the highest for any part of the world: a startling 195 per cent increase, from 19 million in 1995 to 54 million in 2025!
Do you know?
The prevalence of diabetes in the general population is on the increase; it is estimated to be around 13 per cent in the urban population and five per cent in the rural population.
Of these diabetic patients, nearly 20 per cent develop diabetic retinopathy.
A third of people with diabetes never know that they have diabetes; just 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 diabetic is 25 times more likely to go blind than a person in the general population.
The annual cost of treating a diabetic at risk is much lower than the welfare benefits paid to a blind person per annum, particularly in some Western countries.
Diabetes is a serious disorder that can cause blindness, heart disease, kidney failure, and amputations.
But by taking good care of yourself through diet, exercise, and special medications, you can control diabetes.
And there is more good news; diabetes related visual loss due to diabetic retinopathy can be treated before visual loss occurs.
What is diabetic eye disease?
The eye functions very much like a camera. In a normal eye, light enters through the front part of the eye, the cornea and gets focused 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 disease refers to a group of eye problems that people with diabetes may develop as a complication of this disease. All can cause severe vision loss or even blindness. Diabetic eye disease includes: Cataract-clouding of the eye's lens, Glaucoma-increase in fluid pressure inside the eye that leads to optic nerve damage and loss of vision, and Diabetic retinopathy — damage to the blood vessels in the retina. In addition, diabetes can 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.
Who is at risk for diabetic retinopathy? What is diabetic retinopathy? How does it damage the retina?
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 people with diabetes will develop some degree of diabetic retinopathy during their lifetime.
In a diabetic patient, the retina gets affected.
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 blurring of vision in diabetics.
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 eye. 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.
What are the 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 sleep.
Tips: Remember that even in advance cases, the disease may progress a long way without symptoms; hence, regular eye examinations for people with diabetes are so important.
How is the diabetic retinopathy detected?
There is an eye examination that includes:
Visual acuity test: This eye chart tests how well you see at various distances.
Pupil dilation: your eyes should be dilated during the examination; this means eyedrops are used to enlarge your pupils. This allows the eye doctor to see more of the inside of your eyes by an instrument known as indirect ophthalmoscope to check for diabetic retinopathy. After the examination, close-up vision may remain blurred for several hours.
Ophthalmoscopy: this is an examination of the retina with the doctor using a special instrument, wearing a headset with a bright light, looks through a special magnifying glass and gains a wide view of the retina.
Fluorescein angiography (FA): At times, detailed retinal examination is coupled with a special dye test — fluorescein angiography. This test demonstrates the area of leak from blood vessels. In this test, a small amount of dye (fluorescein) is injected into a vein in the arm and pictures are taken as the dye passes through the retinal blood vessels of the eye. Usually this test is done as an outpatient procedure.
How is it treated?
There are two treatments for diabetic retinopathy. They are very effective in reducing vision loss from this disease. In fact, even people with advanced retinopathy have a 90 per cent chance of keeping their 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 of these treatments are very successful, they do not cure diabetic retinopathy.
Laser surgery
Laser treatment, once again, is done in the office as an outpatient procedure. Before treatment, pupils are dilated and drops are applied to numb the eye; in some cases, the doctor may also numb the area behind the eye to prevent any discomfort.
The light in the office will be dim and holding a special lens to your eyes laser is performed. During the treatment, you may see flashes of light. After the treatment, you might need someone drive you back; for the rest of the day, your vision will be a little blurry.
Laser treatment is done to treat both diabetic macular edema and proliferative diabetic retinopathy. Timely laser surgery can reduce vision loss from macular edema by half. But you might require laser surgery more than once to control the leaking fluid. Laser light helps in sealing leaking vessels to stabilise the vision and prevent further visual loss.
Similarly, laser surgery is used to destroy new and abnormal blood vessels that form at the back of the eye. In such cases, rather than focus the laser light on a single spot, hundreds of small laser that burn away from the centre of the retina are placed. This is called scatter laser treatment. The treatment shrinks the abnormal blood vessels. You might lose some of your side vision after this treatment to save the rest of your sight. Laser surgery may also slightly reduce your colour and night vision.
Tips: Remember laser treatment for macular edema does not improve the vision; it only stabilises it. Likewise, patients with proliferative diabetic retinopathy will always be at risk for bleeding.
Vitreous surgery
Instead of laser surgery, some patients may require an eye operation called a vitrectomy to restore some mobile vision. This procedure is performed to remove blood from inside the eye.
Early surgery is recommended in type I diabetics as these patients have a greater risk of blindness from complications of proliferative diabetic retinopathy.
Vitrectomy is done under local anaesthesia; this means you will be awake during the operation. Your surgeon will make a tiny hole in the sclera, or white of the eye. Next, small sized instruments (about 1mm in diameter) are placed into the eye in order to achieve surgical goals. In selected patients who have developed a very advanced stage of diabetic retinopathy, not only do they have a risk of bleeding but also carry significant risk of retinal detachment. Presence of retinal detachment makes the operative procedure more complex; these patients require some kind of tamponade at the end of surgery — either gas or silicone oil; and overall visual improvement is very guarded.
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.
Tips: 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 diabetic retinopathy 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
Good control of blood pressure
Avoiding smoking
Exercising regularly
Maintaining a healthy diet
If diabetes is diagnosed before the age of 30 years, please have an eye examination within five years of diagnosis.
If the diabetes is diagnosed after the age of 30 years, 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 months of pregnancy.
The most important factor for the development of diabetic retinopathy is the duration of diabetes.
Dr. Tarun Sharma is with the Sankara Nethralaya, Chennai.
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