Diabetic Macular Edema

What is diabetic macular edema or DME?

Diabetic macular edema (DME) is a serious eye disease that can affect people with diabetes (1; 2). DME belongs to a group of diabetic eye diseases that can not only cause severe damage to your eyesight but are also the leading cause of blindness in working-aged adults (20–65 years) worldwide (3).

People with diabetes who have high blood sugar (glucose) levels over a long period of time are at risk of getting DME (1; 4). At the start, high levels of glucose damage small blood vessels in the retina, a light-sensitive tissue in the back of the eyes.

The damaged blood vessels start to bleed and leak fluids into the eye. The build-up of fluids causes swelling (known as edema) in an area of the retina called the macula. The swelling around the macula that results is known as diabetic macular edema, or DME.

Because the macula is responsible for sharp vision and seeing objects directly in front of you (known as central vision), swelling of this part of the eye can affect your ability to read or see faces clearly (2). Certain lifestyle and diabetes-related factors may increase your risk of developing DME (2; 5).

(Fig 1) DME is a disease affecting blood vessels in the back of the eye, which causes vision problems and blindness. The below pictures show the parts of the eye where damage occurs in DME

What are the risk factors for DME?

Although living with diabetes increases the risk of getting eye diseases, there are other causes (called risk factors) that can increase the risk of getting DME (5):

• Risk factors that can be controlled (5)
  • High blood sugar (glucose) levels
  • High blood pressure
  • High cholesterol levels
  • Smoking
• Risk factors that cannot be controlled (4; 5)
  • Duration of diabetes – The longer you have lived with diabetes, the greater your risk of getting DME. The risk of getting a diabetic eye disease increases by up to 20% for people who have lived with diabetes for more than 20 years

What are the symptoms of DME?

Symptoms of eye diseases may not be noticeable during the early stages of diabetes. However, as blood vessels start to leak and fluids build up over time in the macula, your vision can worsen dramatically (1).

Some of the main symptoms of DME affecting your eyesight are listed below (1; 2):

• Vision may be blurred
• Objects may change size
• Colours might appear dull or faded
• Seeing in bright or glaring light may be difficult
• Reading or driving may be difficult
• Gaps or dark spots may appear in your vision

(Fig 2) Symptoms of DME can affect your vision in different ways. The below pictures show how the same image might be seen by a person with DME

How is DME diagnosed?

DME may be diagnosed during one of your regular eye screening visits, which should be a key part of your diabetes care. You will be given different exams by your doctor to test your vision (6; 7). Below are a few examples of possible eye tests:

• Eye chart exam: Your ability to read from a distance (also known as visual acuity) will be examined using an eye chart with different sized letters. Based on which letters you are able to read, your doctor can evaluate whether your vision has changed since your last visit
• Dilated eye exam: Your doctor will place eye drops on the surface of your eyes. The drops widen your pupils, which allows your physician to see the back of your eyes, specifically the retina, more clearly

(Fig 3) Two examples of the types of screening eye exams you may experience

If changes in your vision or retina have been found, your doctor will suggest follow-up tests (6). Two common tests that can give an even clearer picture of the retina and the severity of the changes in your eye are described below. Results from these tests help your eye care specialist to diagnose whether you have a diabetic eye disease and can help to find the most appropriate treatment (6; 7):

• Optical coherence tomography (OCT): OCT is like an ultrasound but uses light rather than sound to make a map of the different layers of the retina. This test is painless and helps to measure the amount of swelling in the retina that is caused by the leaky blood vessels (6)
• Fluorescein angiography (FA): During this test, a special dye is injected into the bloodstream. The dye travels through the body and into the eye, where it lights up blood vessels. Photographs can then be taken of the retina that show whether blood vessels are normal or leaking (6)

What treatment options are available for DME?

Once you have been diagnosed with DME, there are several available treatment options that can help to stop or reduce vision loss. In the first place, your doctor will aim to improve the control of your diabetes, including the below changes to your lifestyle (1):

• Changing your diet to maintain a healthy weight
• Increasing the amount you exercise
• Helping you to quit smoking
• Closely monitoring blood sugar (glucose) levels to ensure they are under control

Your physician will also suggest medical treatments to recover or stop vision loss, which can be used alone or together. These treatments include procedures directly involving the eye, such as injections and implants; however, your eye care specialist will ensure the procedures are painless by numbing your eyes with an anaesthetic first (6)

• Anti-VEGF treatment: Anti-VEGF treatments, also known as VEGF inhibitors, are medicines that target the protein VEGF (vascular endothelial growth factor). VEGF, at high levels, can trigger abnormal blood vessel growth and bleeding. Blocking VEGF with anti-VEGF treatments stops the leaking of fluids, swelling of the macula, and abnormal blood vessels from growing (2; 7). Anti-VEGF treatments improve your vision and may be the first choice of drugs your physician will suggest (2; 7)
• Steroid treatment: Steroids can be injected, either directly or using a slow-release implant, into the eye and can help reduce inflammation that contributes to the symptoms of DME (2)
• Laser treatment: A laser is used to seal leaking blood vessels. This slows down the abnormal leakage of blood and reduces the fluid build-up in the macula region of the eyes. In turn, the swelling reduces, which stops your eyesight from getting worse (7; 8); however, actual improvements in vision only happen in some cases (6)

(Fig 4) Treatment options for DME include anti-VEGF injections, steroids (implant), and laser

• New treatments exploring new pathways: Researchers are constantly looking for new and better ways to detect, prevent, and treat vision loss in DME. This also includes the testing and comparison of new therapies to find the best treatments for you

Summary

If you have diabetes, it is important to attend regular screening sessions to test your eyesight and maintain a healthy lifestyle.