Diabetic Macular Oedema (DMO)

What is the Macula?

The retina functions like a layer of photographic film lining the back of your eye and it contains specialised cells that are needed for sight. The very important central area of the retina that lets you see the colours and details is called the macula.

What is Diabetic Macular Oedema (DMO)?

Diabetes can cause damage to the capillaries, including the fine blood vessels of the macula.

Give sufficient diabetic damage, the capillaries of the macula start to leak fluid and protein, causing the macula to become swollen and ‘water logged’. This is known as Diabetic Macular Oedema (DMO).

What are the risk factors of DMO?

The main risk factors are the duration of diabetes, less-than-ideal control of diabetes, and high blood pressure.

What are the symptoms of DMO?

DMO causes distortion and blurring of the central vision and this usually results in difficulty with detailed visual tasks such as reading, watching television, driving and recognising faces.

How is DMO diagnosed?

The diagnosis of DMO is made by a combination of clinical examination (dilated fundoscopy) and Optical Coherence Tomography (OCT) in most cases. The OCT is an entirely non-invasive laser scanning test that produces a detailed cross-section picture of the macula. OCT can look at the extent of the swelling in the macula caused by the capillary leakage in DMO. OCT also allow us to monitor the effect of the treatment at subsequent visits.

Occasionally, Fluorescein Angiography is performed to confirm the diagnosis of DMO. Fluorescein Angiography is a more invasive photographic-dye test. It is performed by injecting a dye (Fluorescein) into the vein in the arm to photograph the abnormal network of blood.

What treatments are available for DMO?

As DMO is effectively the manifestation of Diabetes in the eye, the treatment for DMO includes optimising the following system risk factors:

  • Improve the control of Diabetes.
  • Improve the control of Blood Pressure.
  • Improve the control of ‘lipid profile’.

In addition to these systemic measures, the following ‘eye-specific’ treatments can be used to treat DMO:

  • Laser treatment. This is the conventional treatment for DMO, useful for treating DMO that is not directly involving the central vision. However, when DMO is very close to, or involves the very centre of the macula, laser treatment can have the undesired effect of producing scarring in the central vision.
  • Pharmacological treatment by Intravitreal Therapy. This is when medication is injected into the main eye cavity, the vitreous, to treat DMO. This is the modern treatment that is preferable in most cases of DMO, especially when DMO is very close to or involves the central vision.

There are two main classes of medication which are effective in the treatment of DMO. These are:

    1. Anti-VEGF therapy
    2. Steroid therapy

What is Anti-VEGF Therapy?

The leaking capillaries in DMO, once established, are dependent on signalling molecules, the Vascular Endothelial Growth Factor (VEGF), to keep leaking.

Anti-VEGF agents are engineered humanized antibodies against VEGF. They work by blocking all the effects of VEGF on the leaking capillaries in DMO, therefore ‘drying up’ the macula in DMO.

Anti-VEGF agents are given by Intravitreal Therapy (IVT) of repeated injections into the vitreous cavity, the main eye cavity at the back of the eye.

What Anti-VEGF agents are available?

There are currently three Anti-VEGF agents which are effective and routinely used in the treatment for DMO.

  • Bevacizumab (Avastin)
  • Ranibizumab (Lucentis)
  • Aflibercept (Eylea)

What is Steroid Therapy?

Steroid Therapy, in the form of Ozurdex slow-release steroid implants, are the alternative form of Intravitreal Therapy to Anti-VEGF which is also effective in the treatment of DMO. This is especially the case if the DMO is very severe and chronic (has been present for a long time).

How do I choose between the different treatment options?

The choice of DMO treatment depends on the nature of your condition, and other funding/economic considerations. Your surgeon will discuss the choice of Anti-VEGF agents with you in detail.

What are the aims of treatment?

Intravitreal Therapy (IVT) with Anti-VEGF agents or Steroid (Ozurdex) is able to stop further deterioration of the central vision in the majority of patients (90%) with DMO. Furthermore, a small proportion of patients (20-30%) can experience major improvements in their vision.

However, the main aim of the treatment is to stop the decline in vision. It can be difficult to accurately predict whose vision will improve with the treatment on an individual patient basis, but the vision is very likely to stabilise in the vast majority of patients.

To maintain the effects of treatment, you will likely need to receive regular check-up visits, with repeated IVT treatment of either Anti-VEGF agents or Steroid (Ozurdex) from your surgeon.

What is Intravitreal Therapy?

Intravitreal Therapy (IVT) is a commonly performed procedure that delivers medicine to the main cavity of the eye, the vitreous cavity, by injection. Intravitreal drug delivery has become a popular method of treatment for many retinal diseases.

What are the side effects of Intravitreal Therapy?

  • Subconjunctival haemorrhage: The white of the eye, where the injection went in, is likely to go red. This is harmless and should disappear in a few days.
  • Floaters: You may see a few ‘floaters’ or ‘spots’ in your vision. These spots are normal and should go away within a few days.
  • Discomfort: You may experience some discomfort for the first 24-48 hours after IVT. These are often described as ‘gritty’ and ‘achy’ sensation, and usually resolves after 48 hours. If you experience discomfort after IVT, Paracetamol and/or Ibuprofen in the first 24-48 hours should help resolve these symptoms.

What are the risks of having intravitreal injections?

IVT is a commonly performed procedure that has a very good safety profile. However, there are some potential risks which are very rare:

  • Infection; The most serious complication related to the injection of any medicine inside the eye is infection. Infection can lead to potentially serious loss of sight. The risk of infection is approximately 1 in 1000.
  • Retinal Detachment. There is also a very small risk of retinal detachment estimated at 1 in 1000.
  • Cataract. If you have a pre-existing cataract, this can sometimes progress following IVT. Cataract surgery can however be carried out at a later date.

One of the most feared complications in IVT is an infection developing in the eye after injection (Endophthalmitis). At the Medical Eye Clinic, all IVTs are performed in our state-of-art Operating Theatre, in contrast to the Outpatient Clean Room facility where the majority of IVT takes place in other Eye Clinics or the NHS.

In the Medical Eye Clinic Operating Theatre, our advanced ‘Clean Air’ filtration system ensures that IVT is delivered in the very best sterile environment.

What happens on the day of treatment?

  • On the day of your injection please do not wear makeup. You can eat and drink as normal before the injection.
  • When you arrive for IVT, you will be ‘checked-in’. You will be asked to confirm any allergies you might have and a name band will be placed on your wrist.
  • Eye drops will be given to dilate your pupil and antibiotic drops will be given to prevent infections.
  • You will be asked to sign a consent form before your first injection. The consent is given for a ‘course’ of IVT, and therefore will be valid for subsequent injections.

The procedure:

  • The procedure will take place in our state-of-the-art Operating Theatre.
  • Your eye and the skin around your eye will be cleaned to avoid infection.
  • Your face and the area around the eye will be covered with a special drape.
  • A device will be used to hold your eye open.
  • Your eye will be numbed with an anaesthetic drop so that there is minimum discomfort.
  • Your eye surgeon will then give the injection into the white part of your eye.
  • You may feel a little pressure on the eye when the injection is being given.
  • The treatment should take about 15 minutes.

What can I expect after the treatment?

  • You will be given antibiotic eye drops to use 4 times a day for 5 days.
  • There are no restrictions on resuming normal activities.
  • Your surgeon will usually arrange to see you for a check-up appointment 4 weeks’ after the injection, or 4 weeks following a course of injections.
  • There is usually some discomfort for a few days after an injection. You are likely to experience some gritty sensations in your eye. This is normal and should resolve within a few days. The discomfort can be help by taking Paracetamol or Ibuprofen for the first 24-48 hours after IVT.

However, if you experience any of the following symptoms, please contact your surgeon urgently:

  • Severe pain
  • Loss of vision
  • Redness in your eye that continues to get worse

Written by - Roland Ling BM, Bch (Oxford); FRCOphth