Diabetic Macular Oedema

Living with diabetes requires diligent management of blood sugar levels to prevent a host of potential complications. One such serious complication that can significantly impact quality of life is diabetic retinopathy, a condition affecting the blood vessels in the retina. A further complication of diabetic retinopathy is diabetic macular oedema (DME). This condition arises when fluid leaks from damaged blood vessels in the retina and accumulates in the macula, the central part of the retina responsible for sharp, detailed vision.

Diabetic macular oedema can develop at any stage of diabetic retinopathy, although it is more common as retinopathy progresses.

Diabetic macular oedema (DME) is a build-up of fluid in the macula, a small but vital area in the centre of the retina. The retina is the light-sensitive tissue at the back of the eye, and the macula is responsible for sharp, central vision needed for tasks like reading, driving, and recognising faces. Think of the macula as the high-definition centre of your visual field.

In individuals with diabetes, persistently high blood sugar levels can damage the tiny blood vessels in the retina. These damaged vessels can become leaky, allowing fluid and proteins to seep into the surrounding retinal tissue, including the macula. This fluid accumulation causes the macula to swell, leading to a condition known as oedema.

The swelling of the macula disrupts its normal function, distorting and blurring central vision. The severity of vision impairment depends on the amount of fluid build-up and the duration of the oedema. Untreated DME can lead to progressive and potentially irreversible vision loss. It's important to understand that DME is a complication of diabetic retinopathy, meaning that damage to the retinal blood vessels due to diabetes is a prerequisite for its development. However, not everyone with diabetic retinopathy will develop DME.

While the underlying mechanism of fluid leakage in the macula remains the same, diabetic macular oedema can be broadly categorised based on its characteristics and the pattern of fluid accumulation observed during diagnostic imaging:

• Focal Diabetic Macular Oedema: This type is characterised by localised areas of fluid leakage, often associated with microaneurysms (tiny bulges in the blood vessel walls) or other specific vascular abnormalities in the retina. Laser treatment is often effective in targeting these specific leakage points.
• Diffuse Diabetic Macular Oedema: In this type, the fluid build-up is more widespread across the macula, without clearly defined focal leakage points. This can be more challenging to treat with traditional focal laser therapy and may require other treatment modalities like intravitreal injections.
   

More recently, optical coherence tomography (OCT), a sophisticated imaging technique, has allowed for a more detailed classification of DME based on the structural changes in the retina:

• Cystoid Macular Oedema (CMO): This is a common pattern where fluid accumulates in cyst-like spaces within the layers of the macula. On OCT scans, this appears as dark, fluid-filled cavities.
• Serous Retinal Detachment: In some cases, fluid can accumulate beneath the neurosensory retina (the light-sensitive layer), causing a separation from the underlying retinal pigment epithelium. This is seen as a distinct elevation on OCT.
• Tractional Macular Oedema: This type occurs when scar tissue on the surface of the retina or within the vitreous gel (the jelly-like substance filling the eye) pulls on the macula, causing swelling and distortion. This often requires surgical intervention to release the traction.

The primary cause of diabetic macular oedema is the damage to the small blood vessels in the retina resulting from prolonged high blood sugar levels associated with diabetes. This damage, known as diabetic retinopathy, leads to a cascade of events that ultimately result in fluid leakage into the macula. Here's a more detailed breakdown of the underlying processes:

Hyperglycaemia (High Blood Sugar): Chronic elevation of blood glucose levels damages the endothelial cells that line the walls of the retinal blood vessels. This damage weakens the vessel walls and impairs their normal function.
 

Increased Vascular Permeability: The damaged blood vessels become more permeable, meaning they allow substances that should normally stay within the vessels to leak out. This includes fluid, proteins, and lipids.
 

Breakdown of the Blood-Retinal Barrier: The retina has a tight barrier (the blood-retinal barrier) that prevents the passage of large molecules from the bloodstream into the retinal tissue. High blood sugar can disrupt this barrier, further contributing to leakage.
 

Release of Vascular Endothelial Growth Factor (VEGF): In response to retinal damage and reduced oxygen supply (ischaemia), the eye produces increased levels of VEGF. VEGF is a signalling protein that promotes the growth of new blood vessels (neovascularisation) and also significantly increases vascular permeability, exacerbating the leakage and swelling in the macula.
 

Inflammation: Chronic inflammation in the retina, triggered by the metabolic abnormalities associated with diabetes, also plays a role in the development and progression of DME. Inflammatory mediators can further damage blood vessels and contribute to fluid accumulation.
 

Formation of Microaneurysms: These tiny bulges in the walls of retinal capillaries are a hallmark of diabetic retinopathy. They are fragile and prone to leakage.
 

Blockage of Retinal Capillaries: In some cases, retinal capillaries can become blocked, leading to areas of poor blood flow and oxygen deprivation. This can trigger the release of VEGF and further contribute to DME.

• Blurred or Distorted Central Vision: This is often the first and most noticeable symptom. Straight lines may appear wavy or crooked. Difficulty focusing on fine details, such as when reading or threading a needle, may also occur.
• Reduced Visual Acuity: Overall sharpness of vision, particularly central vision, may decrease. This can make it difficult to recognise faces or read small print.
• Changes in Colour Perception: Colours may appear faded or less vibrant than usual.
• Difficulty with Night Vision: Some individuals may experience increased difficulty seeing clearly in low-light conditions.
• Floaters: While floaters are common and often harmless, a sudden increase in the number of floaters or the appearance of dark spots in the vision can sometimes be associated with diabetic retinopathy and potentially DME. It's important to report any sudden changes to an eye doctor.
• Scotoma (Dark or Empty Spot in Central Vision): In more advanced cases, a dark or blank spot may appear in the centre of the visual field, significantly impairing central vision.

Diagnosing diabetic macular oedema involves a comprehensive eye examination by an ophthalmologist. Several tests and procedures are used to assess the retina, macula, and overall eye health:

Visual Acuity Test: This standard eye test measures how well you can see at different distances using an eye chart (like the Snellen chart). It helps determine the sharpness of your central vision.
 

Pupil Dilation: Eye drops are used to widen (dilate) the pupils, allowing the ophthalmologist to get a clearer view of the retina and macula at the back of the eye.
 

Ophthalmoscopy: Using a special instrument with a light and magnifying lenses, the ophthalmologist examines the retina and macula for signs of damage, such as leaky blood vessels, swelling, and fluid accumulation.
 

Optical Coherence Tomography (OCT): This non-invasive imaging technique uses light waves to create detailed cross-sectional images of the retina. OCT is crucial for diagnosing DME as it can precisely measure the thickness of the macula and identify fluid build-up, even in the early stages. It helps to quantify the oedema and monitor its response to treatment.
 

Fluorescein Angiography (FFA): In this procedure, a fluorescent dye (fluorescein) is injected into a vein in your arm. As the dye travels through the blood vessels in the retina, special cameras take photographs. FFA helps to identify leaking blood vessels, areas of poor blood flow, and the extent of retinal damage. It can be particularly useful in guiding laser treatment.
 

Clinical Examination: The ophthalmologist will also take a detailed medical history, including the duration of your diabetes, your blood sugar control, and any other relevant medical conditions.

The primary goal of treating diabetic macular oedema is to reduce fluid leakage in the macula, decrease swelling, and preserve or improve vision. Treatment strategies are tailored to the individual based on the type and severity of DME, as well as other eye conditions. Current treatment options include:

Anti-VEGF Injections: These are the first-line treatment for many cases of DME. Anti-VEGF (vascular endothelial growth factor) drugs are injected directly into the vitreous gel inside the eye. These drugs block the action of VEGF, a protein that promotes the growth of abnormal blood vessels and increases vascular permeability, both of which contribute to fluid leakage and swelling in the macula. Commonly used anti-VEGF drugs include aflibercept (Brand available: Eylea), ranibizumab, and bevacizumab. Injections are typically given monthly initially, with the frequency adjusted based on the patient's response.
 

Laser Photocoagulation: This involves using a laser to target and seal leaking blood vessels in the retina.

• Focal Laser: Used for focal DME, this treatment targets specific microaneurysms or areas of leakage identified on fluorescein angiography.
• Grid Laser: Used for diffuse DME, this involves applying a grid pattern of laser spots to the central retina to reduce overall swelling. However, grid laser is less commonly used now due to the effectiveness of anti-VEGF therapy.

Corticosteroid Injections or Implants: Corticosteroids are anti-inflammatory drugs that can also help reduce macular oedema. They can be injected into the vitreous cavity or delivered via slow-releasing implants that are inserted into the eye. While effective in some cases, corticosteroids have potential side effects, such as increased eye pressure (glaucoma) and cataract formation, so their use may be more limited or reserved for specific situations.
 

Vitrectomy Surgery: This surgical procedure may be necessary in cases of tractional macular oedema, where scar tissue is pulling on the macula. Vitrectomy involves removing the vitreous gel and any associated scar tissue to relieve the traction and reduce swelling. It may also be considered in cases where other treatments have not been effective.
 

Blood Sugar Control and Management of Systemic Risk Factors: While not a direct treatment for DME, strict control of blood sugar levels, blood pressure, and cholesterol is crucial in managing the underlying diabetes and preventing further damage to the retinal blood vessels. Working closely with your primary care physician or endocrinologist to optimise diabetes management is essential.
 

The choice of treatment or combination of treatments depends on the individual's specific situation and is determined by the ophthalmologist. Regular follow-up appointments and monitoring are necessary to assess the response to treatment and make any necessary adjustments.

Several factors can increase the risk of developing diabetic macular oedema in individuals with diabetes:

• Duration of Diabetes: The longer a person has diabetes, the higher their risk of developing diabetic retinopathy and subsequently DME.
• Poor Blood Sugar Control (Hyperglycaemia): Persistently high blood glucose levels are the primary driver of damage to the retinal blood vessels. Poor glycaemic control significantly increases the risk of DME.
• High Blood Pressure (Hypertension): Elevated blood pressure can further damage the blood vessels in the retina, increasing the likelihood of leakage and swelling.
• High Cholesterol (Hyperlipidaemia): High levels of cholesterol and other fats in the blood can contribute to the development of vascular problems, including those in the retina.
• Pregnancy: Women with diabetes may have an increased risk or worsening of diabetic retinopathy and DME during pregnancy.
• Kidney Disease (Nephropathy): Diabetic kidney disease is often associated with more severe diabetic retinopathy and a higher risk of DME.
• Smoking: Smoking damages blood vessels throughout the body, including those in the retina, and can worsen diabetic retinopathy and increase the risk of DME.
• Obesity: Obesity is often linked to poor blood sugar control, high blood pressure, and high cholesterol, all of which are risk factors for DME.

Genetic Predisposition: While not fully understood, there may be some genetic factors that make certain individuals with diabetes more susceptible to developing diabetic retinopathy and DME.

If left untreated or poorly managed, diabetic macular oedema can lead to significant and potentially irreversible vision loss. The complications of DME include:

• Progressive Vision Loss: The persistent fluid build-up in the macula disrupts its function, leading to a gradual decline in central vision. This can make it increasingly difficult to perform everyday tasks such as reading, driving, and recognising faces.
• Legal Blindness: In severe cases, DME can progress to the point of legal blindness, significantly impacting a person's independence and quality of life.
• Macular Ischaemia: Chronic swelling and damage to the retinal blood vessels can lead to reduced blood flow (ischaemia) in the macula, further impairing its function and potentially causing permanent vision loss.
• Neovascular Glaucoma: In some advanced cases of diabetic retinopathy (which often precedes DME), the growth of abnormal new blood vessels (neovascularisation) can occur in the iris and drainage angle of the eye, leading to a severe and painful form of glaucoma called neovascular glaucoma.
• Retinal Detachment: While less directly related to DME itself, severe diabetic retinopathy can increase the risk of retinal detachment, which can further complicate vision loss.

Early detection and appropriate treatment of diabetic macular oedema are crucial to prevent or minimise these potentially devastating complications and preserve vision.

Living with diabetic macular oedema can present challenges, but there are strategies to help manage the condition and maintain a good quality of life:

• Follow Your Treatment Plan Diligently: Adhere to the treatment plan recommended by your ophthalmologist, including attending all scheduled appointments and taking any prescribed medications or injections as directed.
• Manage Your Diabetes: Strict blood sugar control is crucial. Work closely with your healthcare team to manage your diabetes effectively through diet, exercise, medication, and regular monitoring.
• Monitor Your Vision: Be aware of any changes in your vision and report them promptly to your eye doctor. Regular self-monitoring of your vision can help detect any worsening of the condition.
• Use Assistive Devices: If you experience vision loss, explore the use of assistive devices such as magnifying glasses, large-print books, and talking devices. Your eye doctor or a low vision specialist can provide guidance on appropriate devices.
• Make Lifestyle Adjustments: Make necessary adjustments to your daily activities to accommodate any vision limitations. This may include improving lighting in your home, using contrasting colours for better visibility, and being cautious when driving or navigating unfamiliar environments.
• Seek Support: Connect with support groups or organisations for people with diabetes or vision loss. Sharing experiences and learning from others can be helpful.
• Maintain a Healthy Lifestyle: Continue to eat a healthy diet, engage in regular physical activity, and avoid smoking. These habits are beneficial for overall health and can help manage diabetes and its complications.
• Protect Your Eyes: Wear sunglasses to protect your eyes from excessive sunlight, and avoid rubbing your eyes.
• Stay Positive: Maintaining a positive attitude can help you cope with the challenges of living with DME. Focus on what you can do and seek support when needed.

Misconception: DME only affects people with long-standing diabetes.
Fact: While the risk of DME increases with the duration of diabetes, it can develop at any stage of diabetic retinopathy, even in individuals who have been recently diagnosed with diabetes.

Misconception: If I don't have any symptoms, I don't need to worry about DME.
Fact: DME can develop without noticeable symptoms in its early stages. Regular eye examinations are crucial for early detection, even if you are not experiencing any vision changes.

Misconception: DME is just a minor inconvenience and doesn't cause serious vision loss.
Fact: Untreated DME can lead to significant and potentially irreversible vision loss, including legal blindness.

Individuals with diabetes should see an ophthalmologist for a comprehensive eye examination at least once a year, or more frequently if recommended by their eye doctor. It is crucial to seek prompt medical attention if you experience any of the following symptoms:

• Blurred or distorted central vision
• Reduced visual acuity
• Changes in colour perception
• Difficulty with night vision
• A sudden increase in the number of floaters or the appearance of dark spots
• Any other sudden or significant changes in your vision

Early detection and treatment of diabetic macular oedema can significantly improve the chances of preserving your vision.

If you have been diagnosed with diabetic macular oedema, it is important to have open communication with your ophthalmologist. Here are some questions you may want to ask:

• What type of DME do I have?
• How severe is my DME?
• What are my treatment options?
• What are the risks and benefits of each treatment?
• How often will I need treatment?
• What is my prognosis?
• What can I do to manage my diabetes and reduce my risk of further vision loss?
• Are there any support groups or resources available for people with DME?
• What are the potential side effects of the treatments?
• How will the treatment affect my daily life?
• How often will I need follow-up appointments?

Diabetic macular oedema is a serious complication of diabetes that can lead to significant vision loss if left untreated. However, with early detection, appropriate treatment, and diligent management of diabetes, individuals with DME can often preserve their vision and maintain a good quality of life. Regular eye examinations are crucial for early diagnosis, and adherence to treatment plans and a healthy lifestyle are essential for managing the condition.