Diabetes and eye health

What is diabetes?

Diabetes develops when your blood glucose (sugar) is too high. The pancreas produces insulin, which drives glucose from the blood into your body’s cells, where it is needed for energy. In diabetes, not enough insulin is produced or your cells don’t respond to it well, resulting in high blood sugar levels.

There are three types of diabetes

Type 1 is a genetic condition which is usually identified early in life, when the body produces no insulin. The immune system attacks the pancreatic cells that make insulin.

Type 2 occurs most commonly in middle-aged to older people, when insulin is not used efficiently (insulin resistance), or not enough insulin is produced (insulin deficiency). Type 2 diabetes is largely avoidable, as it usually develops in people who are overweight and lack physical activity. The location of body fat may also affect its development.

Gestational diabetes may develop while you are pregnant.

You may develop diabetic retinopathy in your eyes as a result

Diabetes affects your whole body

When you have too much glucose in the bloodstream, the blood vessels and nerves that run throughout your body can be damaged. Think of your blood vessels as being like steel pipes, and sugar as being like salt. Excess sugar in your blood vessels damages them, just like how salt will rust steel pipes.

complications of diabetes eye health

While the disease is caused by a problem with your pancreas and insulin, it is, in effect, a disease that affects almost every organ. And this includes your eyes.

There are several symptoms of diabetes, notably a weight loss, persistent hunger and thirst, frequent urination and foot numbness – and changes in the eye.

While there is no permanent cure for diabetes, it can be controlled well by tracking your blood sugar, eating fresh vegetables and fruit, getting exercise, stopping smoking and taking the necessary medications.

Diabetes and eyes

Interestingly, diabetes might be first identified through changes in vision: blurry vision, double vision, difficulty driving at night, and frequent changes to your glasses prescription. Several eye diseases are directly caused by diabetes.  They are often referred to under the umbrella term of diabetic eye disease, which is a leading cause of blindness worldwide.

Diabetes can cause:

  • Diabetic retinopathy is an eye disease that diabetics frequently develop, but it is not as well-known as other diabetic complications.
  • Diabetic macular oedema (which often accompanies diabetic retinopathy)
  • Cataract
  • You have a higher risk of developing glaucoma if you are diabetic.

Diabetic Retinopathy

Diabetic retinopathy occurs with both Type 1 and Type 2 diabetes and can develop at any age. The risk increases the longer you have had diabetes, and if you don’t control your blood sugar well.

As the name suggests, diabetic retinopathy occurs when the blood vessels of the light-sensitive tissue at the back of the eye – the retina – are damaged by high blood sugar. The retina is a group of cells that take in light and turn it into images that the optic nerve sends to your brain.

diabetic retinopathy eye health diabetes

The blood vessel walls in the retina weaken and bulge, forming tiny pouches (microaneurysms). These leak blood, fluid and cholesterol into the retina. This is what causes the macula to swell. The macula is the central part of the retina that allows us to see detail. When the macula is affected in this way, it is called macular oedema, which will distort your central vision. Eventually, the blood vessels become so damaged that they completely stop blood flow.

Diabetic retinopathy is the most common cause of blindness in people with diabetes. About half of people with diabetic retinopathy will develop macular oedema.

Diabetic retinopathy usually affects both eyes.

There are four stages of diabetic retinopathy

  • Stage 1: mild nonproliferative diabetic retinopathy. This is sometimes called background retinopathy. It means your sight hasn’t yet been affected, but you will need to prevent the problem getting any worse. There may be just a thickening of the retina or presence of tiny blood clots. This stage rarely affects vision or needs treatment, but does indicate that diabetes damage has occurred, and that progression could decrease vision.
  • Stage 2:moderate nonproliferative diabetic retinopathy. The damage is more serious.
  • Stage 3:severe nonproliferative diabetic retinopathy. If there is inadequate control of your diabetes, more blood vessels are blocked with even more leakage of blood and fluid into the retina.
  • Stage 4:proliferative diabetic retinopathy.  In the proliferative stage, the retina is deprived of its blood supply. As a result, new blood vessels grow, but these vessels are abnormal and fragile and they often bleed into the vitreous (the clear gel that fills the back of the eye). A thick sheet of new blood vessels can cause scars that pull the retina away from the back of the eye, which is called a tractional retinal detachment.

diabetic retinopathyHow quickly diabetic retinopathy progresses depends on several factors including blood sugar, blood pressure, cholesterol, and smoking. This is why it is so important that patients control their diabetes with exercise, healthy diet and prescribed medications.

Diabetic retinopathy usually has no symptoms at onset, and most people won’t any symptoms until it reaches Stage 4, or until they develop diabetic macular oedema. While diabetic retinopathy can’t be cured, it can be stabilized with treatment and so an early diagnosis is essential. If it is not treated in time, then you may lose your sight entirely.

How do you ensure early detection of diabetic retinopathy?

Take note of any changes in your eyes. Symptoms include blurry vision, eye floaters, difficulty seeing at night, and distorted vision (seeing straight lines as bent or wavy). High blood sugar levels can temporarily cause blurred vision, that changes as your blood sugar returns to normal. Make an appointment with your optometrist any time that you notice distorted or blurred vision.

dilated eye exam

You may not, however, have any symptoms at all. But if you have diabetes, it is very important to get a comprehensive dilated eye examination at least once a year. Diabetes is a leading cause of preventable vision loss. Early examination can detect any changes in your eye, so that treatment can be started early.

How fast does diabetic retinopathy develop?

Commonly, it will develop three to five years after having been diagnosed with diabetes.  The longer you have diabetes, the more likely you are to develop it. For example, nonproliferative diabetic retinopathy (NPDR) (Stage 1) has been found in 25% of patients five years after they were diagnosed with diabetes, 60% at 10 years, and 80% at 15 years. However, many patients diagnosed with diabetes have been living with diabetes, unknowingly, for several years. These patients will often have diabetic retinopathy at the time of diabetes diagnosis.

Diabetic maculopathy

Diabetic maculopathy, also known as Diabetic Macular Oedema (DMO), is a different type of retinopathy that affects the macula, or middle of the retina. It is possible to get DMO at any stage of diabetic retinopathy. It is critical to keep the macula healthy, as it is the part of the eye that sees detail, and enables us to read, for example.

Macular oedema develops when the macula swells due to leaking fluid. Symptoms of macular oedema include wavy vision and colour changes.

Cataract

Not everybody is aware that diabetes can cause cataract in one or both eyes. Cataract is when the lens inside your eye becomes cloudy. Symptoms of cataract include:

  • faded colours
  • clouded or blurry vision
  • double vision, usually in just one eye
  • sensitivity to light
  • glare or halos around lights
  • vision that doesn’t improve with new glasses or a prescription that must be changed often

Diabetics are at a much higher risk of developing cataract (it is estimated that the risk is two to five times higher) and they may also develop cataracts at a much younger age than non-diabetics. In addition, their cataracts progress much faster. A diabetic patient with cataract may lose all their vision in the affected eye within just six months – much faster than what occurs with typical age-related cataract. This is because diabetic patients develop a specific type of cataract called “posterior subcapsular cataract”. This is a cloudy plaque that grows quickly across the back surface of the human lens. As soon as the plaque covers the pupil, you will no longer be able to see. Fortunately, cataracts are easily cured with surgery, and the results of this operation are typically excellent.

Swelling of the lens

Another eye problem that you may have if you are diabetic is intermittent swelling of the eye’s lens, resulting in transient blurry vision. This can happen if your blood sugar rises very quickly. Once your sugar levels normalise, your vision should return to normal as well.

Glaucoma

Glaucoma is caused by increased pressure inside the eye, which damages the optic nerve. The optic nerve transmits images from your eye to your brain, and it is therefore essential for you to see.

If you are diabetic, you are twice as likely to develop glaucoma – particularly open angle glaucoma – than others. Glaucoma causes loss of your peripheral vision, but by the time this occurs your optic nerve is already severely and irreversibly damaged.

Patients with stage 4 diabetic retinopathy (proliferative diabetic retinopathy), can also suffer a different, very aggressive form of glaucoma. In proliferative diabetic retinopathy, abnormal blood vessels grow inside the eye, including across the iris (the coloured part of your eye). These blood vessels block the fluid drainage channels inside the eye, causing the pressure to rise sharply. This is known as neovascular glaucoma, or rubeotic glaucoma. It requires urgent treatment (within weeks), or vision may be permanently lost.

Treatment of glaucoma involves eye drops and laser. Occasionally surgery is required to create a new fluid drainage pathway for the eye.

Tractional retinal detachment

Stage 4 diabetic retinopathy (proliferative diabetic retinopathy) causes a sheet of abnormal blood vessels to grow across the retina at the back of your eye. This sheet forms a thick scar, and it can physically pull your retina away from the back of the eye, called a tractional retinal detachment. This is like wallpaper being pulled off of a wall. It is a serious eye condition, and you may suffer permanent blindness if it is not treated immediately with an operation.

Strangely enough, a detached retina is not painful. You might notice flashes of light or an increase in the number of floaters, or perhaps a curtain of darkness moving across your vision.

proliferative diabetic retinopathy

This image shows an example of proliferative diabetic retinopathy. Here you can see a sheet of new blood vessels growing across the surface of a patient’s retina. These new blood vessels can bleed and pull the retina away from the back of the eye (a tractional retinal detachment).

Retinal Detachment Treatment

Your eye doctor will decide which of these treatments is most suitable for your case of retinal detachment.

Laser (thermal) or freezing (cryopexy).

These treatments forms a tight seal around the area of retina that has detached, to prevent it from extending.

Scleral buckle

A scleral buckle is a small silicone band that is sewn around the sclera (the white of your eye). It works something like a belt, compressing the eye and making the retina less likely to detach. It is is invisible and permanently attached.

Vitrectomy

Vitrectomy is the operation to remove the gel from the back of your eye (the vitreous humour). Diabetic tractional retinal detachments nearly always require vitrectomy. The gel is replaced by oil, that is later removed, or by gas, which gradually gets absorbed into the bloodstream.

What happens at a diabetic dilated eye examination?

The optometrist or ophthalmologist (eye doctor) will check your vision, as well as looking at the retina and the inside of your eyes. Sometimes a dye is used to show up any leaky blood vessels.

A special camera is used to take pictures of the back of the eyes. You may get eyedrops to make your pupils bigger, which may sting slightly. As the photos are taken, there will be a sudden flash of light. The pictures are sent to a computer which analyses the image and helps your eye doctor determine if you have diabetic retinopathy and grade its severity.

The drops may make your vision blurry, so be careful if you are driving home from the appointment. It’s also a good idea to wear sunglasses afterwards.

Treatment of diabetic retinopathy

Treating diabetic retinopathy can repair damage to the eye and prevent blindness in most patients. Treatment can start before your sight is affected, which helps to prevent vision loss.

Regular checkups

In the early stages, your ophthalmologist will want to keep track, by examining your eyes regularly. If your eye doctor thinks you may have severe diabetic retinopathy, a special test may be done, called a fluorescein angiogram, which examines the blood vessels in your retina.

Laser therapy

Later on, you may require a laser procedure, to stop the progression of the disease. This therapy, also called laser photocoagulation, destroys tiny islands of retina that aren’t important for your eyesight, in order to save your central vision.

Eye medications

When macular oedema has developed, medications may be injected straight into the eye. This sounds scary, but most patients don’t feel the injections at all. The drug injected is usually a Vascular Endothelial Growth Factor (VEGF) inhibitor. VEGF is a protein produced by the diabetic retina, which causes blood vessels to leak fluid, and unhealthy new blood vessels to grow. These injections, by blocking VEGF, clear any retinal swelling, and eradicate abnormal blood vessels. Such injections can even reverse diabetic retinopathy. Corticosteriods may also be injected.

Surgery

Later, surgery may be required.  The ophthalmologist may remove all or part of the vitreous (the clear gel).  This is called a vitrectomy. During this procedure, any scar tissue will be removed, and blood cleared out.

How to avoid vision loss if you have diabetes

If you are diagnosed as diabetic, the best thing you can do for every organ, including your eyes, is to control your blood sugar levels. You can do this by eating healthily, exercising, stopping smoking, not consuming alcohol regularly, and following instructions for all medications.

Having high blood pressure or high cholesterol will increase your risk of diabetic retinopathy. Avoid fluctuations in blood sugar levels, lower your blood pressure and cholesterol, and protect your eyes from the sun by wearing hats and sunglasses. To summarise:

Get a dilated eye exam

At least once a year, get a dilated eye examination, so that your eye doctor can spot any problems early when they’re most treatable.

Keep your blood sugar levels in your target range

Over time, high blood sugar not only damages blood vessels on your retina, but also increase your risk of cataract and glaucoma.

Keep your blood pressure and cholesterol levels in your target range

This lowers your risk for eye diseases and vision loss. It is also very good for your health in general!

Quit smoking

Quitting lowers your risk for diabetes-related eye diseases and improves your health in countless other ways too.

Get active

Physical activity protects your eyes and helps you manage diabetes.

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