Diabetic macular oedema explained

Dr Enslin Uys, an ophthalmologist, unpacks the symptoms, causes, and treatment for diabetic macular oedema.


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Diabetic macular oedema (DMO) is one of the leading, preventable causes of central vision loss. It’s a complication of diabetes that causes fluid build-up in the macula (the part of the eye responsible for the central, detailed vision). This can lead to blurred vision, double vision, and even total loss of vision.

What is the cause?

The retina is the thin nerve layer in the back your eye, like the film in a camera, that receives the image in your eye and sends it to your brain allowing you to see. High blood glucose levels cause damage to the small blood vessels in the retina, leading to fluid leakage and swelling (oedema).

What do you experience?

There are a variety of symptoms, most commonly blurred vision.  You can also have double vision, distorted colours, and blind spots.

How is it diagnosis?

You will need a comprehensive eye examination by an ophthalmologist. Your visual acuity (vision) will be recorded and your eye examined from the front to the back. Your pupils will be dilated, by inserting drops, to give the ophthalmologist a better view of the back of your eyes. Special lenses are used to look at the back of your eyes; this is called a fundoscopy or fundus examination. Special tests or investigations are also performed to assist in the diagnosis, for documentation and monitoring. These tests include:

  1. Colour fundus photos

Image: Left colour photo – DMO circled

  1. Optical Coherence Tomography (OCT)

This is a non-invasive detailed scan of the back of the eye, the retina, almost like a CT scan of the retina.

Image: OCT right – normal.


Image: OCT left – CMO.

  1. Optical coherence tomography angiography (OCTA)

This is also a non-invasive medical imaging technique used to visualise the blood vessels (microvasculature) in the retina.

  1. Fluorescein angiography

This is similar to doing an angiogram of the heart. A drip is inserted in your hand and a dye (fluorescein) is injected into the vein that travels very quickly through the body and gets to your eye within 20 to 30 seconds.

Numerous pictures are taken over a 10-minute period to see if there are areas of ischemia (poor blood supply), or leakage of the dye (as it is not supposed to escape the blood vessels) and where it’s leaking from.

Image: Left fluorescein angiography with leakage circled.

 Risk factors

  • Duration of diabetes: The longer you have had diabetes, the higher the risk of developing DMO.
  • Poorly controlled blood glucose levels: Inadequate control of blood glucose levels over time can increase the risk of diabetic retinopathy and DMO.
  • High blood pressure: Hypertension can exacerbate the damage to blood vessels in the retina, increasing the risk of DMO.
  • High cholesterol levels: Elevated cholesterol levels can contribute to the development and progression of DMO.
  • Pregnancy: Pregnant women with diabetes may be at increased risk of developing DMO due to hormonal changes and fluctuations in blood glucose levels during pregnancy.
  • Other factors: Factors such as smoking, obesity, and genetic predisposition may also play a role in the development of DMO.

Regular eye examinations are important for early detection and treatment to preserve your vision.

How is DMO treated?

Once the diagnosis has been made, a treatment plan will be discussed by your ophthalmologist. The current, most common, form of treatment is anti-vascular endothelial growth factor (VEGF) injections.

Anti-VEGF injections

  • These injections have become the gold standard for treatment of many retinal diseases of which DMO is one of them.
  • Anti-VEGF treatment is given as an injection into the white part of your eye (sclera). The drug is injected directly into the vitreous, the jelly that fills your eye. This is called an intravitreal injection. Your eye is numbed with drops prior to the injection and betadine is inserted to prevent an infection. Although it sounds terrible, the procedure is generally straightforward, quick, and not painful.
  • Initially these injections are repeated every four weeks. This is called the loading dose. The vision and OCT scan are then repeated and the response to the injections evaluated.
    • If a good response was obtained: the interval between injection can then be increased.
    • If a poor response was obtained: you might be switched to a second-line treatment option.
  • For DMO, these injections are usually ongoing over a two to three year-period. All depending on the response.
  • The current anti-VEGFs available in South Africa are bevacizumab, aflibercept, ranibizumab and faricimab-svoa.
  • Although bevacizumab is not registered (used off label), it’s ten times cheaper than the registered drugs and is used as first-line treatment. It has been used for more than 15 years worldwide and has an excellent track record with multiple studies to prove this.
  • Second-line treatment is introduced only when bevacizumab failure has been shown.

Other treatment options include corticosteroid injections, implant or triamcinolone injections, focal laser photocoagulation, or vitrectomy surgery.

Prevention

Manage your diabetes through:

  • Lifestyle changes (see a dietitian, follow a healthy eating plan and exercise three to four times per week).
  • Medication to control your glucose levels.
  • Regular eye examinations.
  • Early treatment of DMO.

If you are experiencing symptoms or have concerns, consult an eye specialist or healthcare professional for personalised advice.

Dr Enslin Uys (MBChB; DA (SA); Dip Ophth (SA); FCOphth (SA)) is a general ophthalmologist with a strong interest in disease affecting the retina. He is the co-founder of the Pietermaritzburg Eye Hospital, where he is currently in full time private practice, and is the current president of the South African Vitreoretinal Society (SAVRS) that represents ophthalmologists in SA involved in treating and managing retinal diseases.

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Dr Enslin Uys (MBChB; DA (SA); Dip Ophth (SA); FCOphth (SA)) is a general ophthalmologist with a strong interest in disease affecting the retina and the co-founder of the Pietermaritzburg Eye Hospital, where he is currently in full time private practice. He is also the current president of the South African Vitreoretinal Society (SAVRS) that represents ophthalmologists in SA involved in treating and managing retinal diseases.


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