Dr. S.M.Sadikot.
Hon. Endocrinologist,
Jaslok Hospital and Research Centre,
Mumbai 400026

Look at the picture below on the left hand side. This is what you would see if you were walking along the road. Now look at the picture on the right. This is what you would see if your eyes are affected with severe diabetic retinopathy!

Terrible, is it not?

This is in no way meant to frighten you. But you must realize that unless you are careful about managing your diabetes, this could happen to you.

If you have diabetes this does not necessarily mean that your sight will be affected, but there is a higher risk. If your diabetes is well controlled then you are less likely to have problems, or they may remain at a mild level.

Although giant strides have been made in the treatment of diabetic retinopathy, the best treatment still remains "prevention" and even if one cannot completely avoid getting the retinal complications, one can definitely slow down its progression, so that it never reaches a level serious enough to cause "blindness"!

But a large part in saving your eyes lies in your hands!

Before, we discuss these aspects, let us first understand what is diabetic retinopathy.
Diabetic retinopathy is a general term for all disorders of the retina caused by diabetes. This is commonest complication of diabetes to do with the eyes. It is a progressive disease that destroys capillaries (the smallest blood vessels linking arteries to veins) in the eye by depositing an abnormal material along the walls of the tiny blood vessels in the retina. Blurred vision and often blindness follow.

The retina is a light-sensitive tissue at the back of the eye. When light enters the eye, the retina changes the light into nerve signals. The retina then sends these signals along the optic nerve to the brain. Without a retina, the eye cannot communicate with the brain, making vision impossible.

To view an interactive lesson in the functions of the various parts of the eye.

Thinking of a camera can help you understand how the eye works. macular or retinal damage.

A camera lens focuses a picture onto a film inside the camera. In our eyes the same thing happens, but the film is replaced by the retina. The retina 'makes' the pictures of the world that we see, converting the light into electrical signals that are then sent on to the brain.

The eye as a camera. Above, the image of the house focusing on the retina. The central part of any image, a house or a person's face for instance, will be clear if the macula is healthy.

The retinal cells stand next to each other, a bit like houses in a street. The main cells are the rods and cones: these are the cells that take up light and convert it into electrical messages, which are then sent onto the brain.

These cells receive their oxygen and other nutrients from tiny blood vessels nearby. These blood vessels are like pipes which pass nearby the cells; imagine a largish pipe passing past your house, containing blood. The walls of these pipes/blood vessels are very thin, and so nutrients can pass through them. These nutrients are the 'food' for the cells.

As you read on, you will understand the major role played by a part of the retina called the "macula".

The macula is the most sensitive part of the retina. It makes out the fine details of the things we look at, peoples' faces, bus numbers, reading and writing, and everything lese we see.

If the macula is damaged all these things you see in fine detail are misty. The picture is still there but you cannot make out any of the detail.

A healthy retina will produce a clear image, like a normal film in a camera. But in macular damage the image will not be clear.

For example if the film was scratched in the middle, the 'scratch' would show up in the middle of the photograph like a black mark or blot of ink. This is similar to damage caused by macular disease such as diabetic maculopathy.

Diabetes causes damage to the blood vessels that nourish the retina, the seeing part at the back of the eye.

There are two types of diabetic retinopathy, non-proliferative or proliferative.

Nonproliferative retinopathy is the common, mild form. It accounts for about 80 percent of all cases.It usually has no effect on vision and needs no treatment. But after it is diagnosed, have your eyes checked at least yearly to make sure it's not getting worse.

For an excellent interactive look at all these retinal changes from the normal to the most serious.

In nonproliferative retinopathy, capillaries balloon and form pouches. Although retinopathy does not usually cause any vision loss at this stage, the retinal vessels weaken and develop bulges (microaneurysms) that may leak blood (hemorrhages) or fluid (exudates) into the surrounding tissue.

The ability to control the passage of substances between the blood vessels and the retina may be lost. As a result, the retina becomes swollen and fatty deposits form within it. If this swelling affects the center of the retina, the "macula", this called macular edema and vision loss can result, as we have seen above.

Your doctor must have either sent examined the inside of your eyes or sent you to an "eye" specialist to have a fundus examination. This is nothing but examining the retina in your eye with the help of an instrument called the "ophthalmoscope".

This is how the retina appear to the doctor if your eyes have not been affected by diabetes.

In order to understand this more clearly, this is a schematic view of a normal eye

The blood vessels can make a special growth chemical (VEGF= vascular endothelial growth factor) that makes other tiny, tiny blood vessels grow. These are called 'new' blood vessels.These new vessels are very delicate and very easily bleed, and this blood can (if the eye is not lasered) damage your eye badly.

If the blood vessels are severely damaged, they close off. In response again, new blood vessels start growing in the retina.

This is 'proliferative retinopathy'.

Usually in this condition, without laser treatment (see below), the sight is very badly affected and people may become blind.

These new vessels are weak and can leak blood, blocking vision, which is a condition called vitreous hemorrhage. The new blood vessels can also cause scar tissue to grow. After the scar tissue shrinks, it can distort the retina or pull it out of place -- this is called retinal detachment.

If the macula is involved, this is a very serious matter. We have seen above that when the macula is involved, the central vision is affected! But this can still be treated in its early stages with laser therapy.

An excellent composite view of the changes which take place in the vessels as retinopathy progresses is given below.

For an excellent interactive look at all these retinal changes from the normal to the most serious.

You must always remember that your retina can be badly damaged before you notice any change in vision. Most people with nonproliferative retinopathy have no symptoms. Even with proliferative retinopathy, the more dangerous form, people sometimes have no symptoms until it is too late to treat them.

And yet, retinopathy is easily diagnosed through an ophthalmoscopic examination. If your doctor sees any evidence of retinal changes, he may then ask you to undergo more tests so that he can treat the problems and prevent further progression to a severe state when vision is seriously affected. There is also some evidence that if diagnosed at an early stage, some of the damage can even be reversible!

For this reason, you must have your eyes examined regularly.

Anyone with diabetes. The longer someone has diabetes, the more likely he or she will get diabetic retinopathy. Nearly half of all people with diabetes will develop some degree of diabetic retinopathy during their lifetime.

Several factors influence whether you get retinopathy. These include your blood sugar control, your blood pressure levels, how long you have had diabetes, and your genes.

The longer you've had diabetes, the more likely you are to have retinopathy. Almost everyone with Type 1 diabetes will eventually have nonproliferative retinopathy. And most people with Type 2 diabetes will also get it. But the retinopathy that destroys vision, proliferative retinopathy, is far less common.

There are steps you can take to avoid eye problems.

First and most important, keep your blood sugar levels under good control.

Many studies have shown the importance of a good control of your blood glucose levels. If you do not have diabetic retinopathy and do NOT keep your diabetes under control, your have FOUR times the chances of getting retinopathy as compared to someone who does keep his diabetes well controlled!

In people who already had retinopathy, the condition progresses in those with good control only half as often as those not well controlled.

In fact, it has been shown that for each 1% rise in the HbA1c, (we have discussed HBA1c or glycoisylated hemoglobin in the section on monitoring control) the retinopathy gets worse at the rate of 32%. So if your HbA1c is 9%, your retina is getting damaged twice as fast as someone with a level of 6% (3 x 32% = 92% additional deterioration).

High blood pressure is fairly common in people with diabetes. Again you should aim for a good control of your blood pressure 130/80 or less [lower still if there is protein in your urine]). With blood pressure, for each 10mmHg rise, the retinopathy gets 11% worse. So if your blood pressure is 150/90, your retina is getting 22% worse that someone whose pressure is 130/80.

Similarly Smoking literally doubles the rate of damage that diabetes causes to the bodies larger arteries, making amputations and heart disease far more likely. Smoking triples the rate of retinopathy progression.

These impressive results show that you have a lot of control over what happens to your eyes!

To sum up,

Lifestyle	30-60 minutes exercise a day, moderate alcohol consumption only, avoid obesity if possible, balanced diet including 5 portions of vegetables or fruit a day, with the minimal of animal or 'hard' vegetable fats, and very low salt.
Blood Pressure	130/80 or less 125/75 or less if protein in urine present
HbA1c	6.5% or less with very few or preferably no hypos.If hypos develop, see expert advice.ACE inhibitors or AT11 unless young/pregnant/very low blood pressure/poorly tolerated
Cholesterol	< 5.0mmol/l, and statins recommended for most adult patients
Smoking	Smoking 20 a day es retinopathy (passive smoking: room-mates inhale at least 25%)

There are usually no symptoms in the early stages of diabetic retinopathy. Vision may not change until the disease becomes severe. An exam is often the only way to diagnose changes in the vessels of your eyes. This is why regular examinations for people with diabetes are so important.

See that your eyes are checked regularly by your doctor for retinopathy.

At the same time, there are some situations which should be considered serious and you should see your doctor at once!

• You have trouble reading signs or books
• You see double
• One or both of your eyes hurt
• Your eyes get red and stay that way
• You feel pressure in your eye
• You see spots or floaters
• Straight lines do not look straight

• You can't see things at the side as you used to

But as we said above, there are no signs or symptoms in the early stages of the disease. Vision may not change until the disease becomes severe. Nor is there any pain.

Even in more advanced cases, the disease may progress a long way without symptoms.

But to protect your vision, comprehensive eye exams are needed every year, or as directed by your physician. Remember, the most dangerous threats to vision in diabetes give little or no warning. Only by direct examination with an ophthalmoscope can these early changes be seen and treatment started before sight becomes seriously threatened.

Although there are quite a few tests which your doctor may carry out, the most important from the viewpoint of diabetic retinopathy detection is an ophthlmoscopic examination of the retina.

Your doctor will use an ophthalmoscope and look at your retina for early signs of the disease, such as:

1. Leaking blood vessels,
2. Retinal swelling, such as macular edema,
3. Pale, fatty deposits on the retina--signs of leaking blood vessels,
4. Damaged nerve tissue, and
5. Any changes in the blood vessels.

During this examination, your doctor may put in some eye drops to dilate your pupils so that he gets a better view of the retina and also to prevent the pupil from contracting when the light from the opthalmoscope falls on the retina. Your vision may be blurred for a few hours after this examination and therefore, please take someone with you when you go for this examination and definitely do not drive to your doctor's clinic!

Your doctor may ask that you have a test called fluorescein angiography.

Fluorescein angiography is an extremely valuable test that provides information about the circulatory system and the condition of the back of the eye. FAs are useful for evaluating many eye diseases that affect the retina.

The test is performed by injecting a special dye, called fluorescein, into a vein in the arm. In just seconds, the dye travels to the blood vessels inside the eye. A camera equipped with special filters that highlight the dye is used to photograph the fluorescein as it circulates though the blood vessels in the back of the eye. If there are any circulation problems, swelling, leaking or abnormal blood vessels, the dye and its patterns will reveal these in the photographs. The doctor can then make a determination as to the diagnosis, and possible treatments.

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 percent chance of keeping their vision when they get treatment before the retina is severely damaged.

This again shows the importance of regular eye checkups!

These two treatments are laser surgery and vitrectomy. It is important to note that although these treatments are very successful, they do not cure diabetic retinopathy.

Laser surgery is performed in a doctor's office or eye clinic. Before the surgery, your ophthalmologist will: (1) dilate your pupil and (2) apply drops to numb the eye. In some cases, the doctor also may numb the area behind the eye to prevent any discomfort.

The lights in the office will be dim. As you sit facing the laser machine, your doctor will hold a special lens to your eye. During the procedure, you may see flashes of light. These flashes may eventually create a stinging sensation that makes you feel a little uncomfortable.

In laser treatment, the doctor makes tiny burns on the retina with a special laser. These burns seal the blood vessels and stop them from growing and leaking.

In scatter photocoagulation (also called panretinal photocoagulation), the doctor makes hundreds of burns in a polka-dot pattern on two or more occasions. Scatter photocoagulation reduces the risk of blindness from vitreous hemorrhage or detachment of the retina -- but it only works before bleeding or detachment has progressed very far.

Side effects of scatter photocoagulation are usually minor. They include several days of blurred vision after each treatment and possible loss of side (peripheral) vision.

In focal photocoagulation, the eye care professional aims the laser precisely at leaking blood vessels in the macula. This procedure does not cure blurry vision caused by macular edema. But it does keep it from getting worse.

For the rest of the day, your vision will probably be a little blurry. If your eye hurts a bit, your doctor can suggest a way to control this.

You may leave the office once the treatment is done, but you will need someone to drive you home. Because your pupils will remain dilated for a few hours, you also should bring a pair of sunglasses.

When the retina has already detached or a lot of blood has leaked into the eye, photocoagulation is no longer useful.

The next option is vitrectomy, which is surgery to remove scar tissue and cloudy fluid from inside the eye. The earlier the operation occurs, the more likely it is to be successful. When the goal of the operation is to remove blood from the eye, it usually works. Reattaching a retina to the eye is much harder and works in only about half the cases.

How Common Are the Other Diabetic Eye Diseases?

If you have diabetes, you are also at risk for other diabetic eye diseases. Studies show that you are twice as likely to get a cataract as a person who does not have the disease. Also, cataracts develop at an earlier age in people with diabetes. Cataracts can usually be treated by surgery.

Glaucoma may also become a problem. A person with diabetes is nearly twice as likely to get glaucoma as other adults. And, as with diabetic retinopathy, the longer you have had diabetes, the greater your risk of getting glaucoma. Glaucoma may be treated with medications, laser, or other forms of surgery.

Self-Testing The Eye

At times, someone who has diabetes can detect changes in their vision that warn of problems. These changes can be found using a simple Amsler grid. Testing with an Amsler grid helps to detect vision changes caused by poor control, macular edema, or a detached retina. The grid is used by doctors to detect eye problems, but it only detects problems in the macula and cannot check other regions of the eye.

Your doctor may ask you to test yourself with an Amsler's Chart.

Anyone who has been told they have significant eye changes caused by diabetes should test each eye daily. If you notice any changes in your vision, see your eye doctor immediately.

The Amsler's chart is very useful for early detection of macular problems and thus is very important as this may be an early sign of macular problems and lead to a loss of central vision! But one must know its limitations.The Amsler grid will NOT detect proliferative diabetic retinopathy, most preproliferative changes and other types of damage that may threaten vision, nor is it useful for detecting any of the early changes. Remember: a normal Amsler grid test does not rule out the presence of retinopathy that can threaten your vision.It cannot replace routine eye exams. Only regular eye exams can do this.

You will realize that protecting yourself against serious diabetes eye complications is in your hands.

Even if one cannot "see" INTO the future, at least one can "see" in the future!!

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