Macular Edema or Diabetic Macular Edema (DME) – Overview

Definition

Macular edema or Diabetic Macular Edema, is swelling or thickening of the eye’s macula, the part of your eye responsible for detailed, central vision. The macula is a very small area at the center of the retina a thin layer of light-sensitive tissue that lines the back of the eye. Light rays are focused onto the retina, where they are transmitted to the brain and interpreted as the images you see. It is the macula that is responsible for your pinpoint vision, allowing you to read, sew or recognize a face.

Macular edema develops when blood vessels in the retina are leaking fluids. The macula does not function properly when it is swollen. Vision loss may be mild to severe, but in many cases, your peripheral (side) vision remains. Macular edema is often a complication of diabetic retinopathy, and is the most common form of vision loss for people with diabetes particularly if it is left untreated.

Epidemiology

Diabetes is the leading cause of new blindness in the United States, and clinically significant macular edema (CSME) contributes greatly to this vision loss. In the absence of ophthalmologic treatment, persons with diabetes have a 25-30% risk of moderate vision loss. With treatment, the risk drops by 50%. According to 2007 data, 23.6 million people in the United States have diabetes, but only 17.9 million have been diagnosed. About 50% of those with diagnosed diabetes do not receive appropriate eye care. The World Health Organization estimates that worldwide, more than 150 million people have diabetes.

Although diabetes is more common in Hispanics, African Americans, and Native Americans than in whites, no data describe a greater risk of developing macular edema among diabetic patients of any one racial group. Likewise, no data describe a difference in risk of diabetic macular edema between the sexes.

Types of Macular Edema

It can be broadly characterized into two main anatomic categories:

• Focal Macular Edema is characterized by specific areas of separate and distinct leakage in the macula with sufficient macular blood flow.
• Diffuse Macular Edema results from leakage of the entire capillary bed surrounding the macula, resulting from a breakdown of the inner blood-retina barrier of the eye.

In addition to Focal and Diffuse, DME is also categorized based on clinical exam findings into clinically significant macular edema (CSME), non-CSME and CSME with central involvement (CSME-CI), which involves the fovea.

Macular Edema Risk factors

Anyone with type 1 or type 2 diabetes is at risk for developing diabetic macular edema (DME) or diabetic retinopathy. Specific risk factors include:

• Duration of diabetes – the longer you have diabetes, the greater your risk of developing diabetic macular edema (DME)
• Chronic high levels of blood sugars
• High cholesterol levels
• Hypertension (high blood pressure)
• Kidney disease
• Heart disease
• Smoking
• Pregnancy

Causes of Macular Edema

Usually the cause is that tiny retina capillaries leak from weak vessel walls into the center of the macula. The patient perceives fogginess in the middle or just to the side of the central visual field, The loss of vision can occur slowly. It rarely causes an enduring loss of vision, but can take 2 to 15 months to heal. Sometimes macular swelling can occur after cataract or other surgery but is, with treatment, usually of temporary duration.

Because many tiny capillaries surround the macula, any condition affecting blood circulation in the body (diabetes, atherosclerosis, etc.) affects the eye; the result may be macular edema. The reason this is important is that macular edema is usually a symptom of a more serious health problem that needs to be addressed. In the case of the latter, macular edema typically occurs within 1-2 months post-surgery; though it can even happen many months, and even years, afterward.

Here is a list of the possible key causes of macula edema:

Oxidative stress: The imbalance between the antioxidant defense system, production of free radicals (reactive oxygen species, ROS), cause oxidative stress in the body and in the tissues of the eye. Damage from ROS causes a host of problems, including inflammation and fluid leakage in the macula and other parts of the eye.

Other eye conditions: Macular edema is caused by many diseases, including optic neuritis, retinal vein occlusion, macular degeneration, diabetic macular leakage, eye inflammation, idiopathic central serous chorioretinopathy, anterior or posterior uveitis, pars planitis, retinitis pigmentosa, radiation retinopathy, posterior vitreous detachment, epiretinal membrane formation, idiopathic juxtafoveal retinal telangiectasia, capsulotomy or iridotomy. These disorders can be due to circulatory problems associated with hypertension, high cholesterol, etc.

Other health conditions: The disorder can be related to general circulatory problems linked to hypertension, high cholesterol, and to nervous system-related conditions such as multiple sclerosis.

Diabetes: A 2006 study of diabetics determined that 9% had macular edema; more recent evaluations find 3.8% in diabetics over 40. High levels of hemoglobin A1c, a biomarker for diabetes, are associated with higher diabetic macular edema risk. Having diabetes for 10 years or longer increases the risk.

Medicines: A history of use of topical epinephrine or prostaglandin analogs for glaucoma is a factor.

Eye surgery: Surgery for cataracts, glaucoma, or other retinal disease can result in macular edema, sometimes months after the surgery. Edema can occur due to post-operative lesions.

Ethnicity: Non-Hispanic Blacks are at greater risk of developing diabetic macular edema.

Injury: If you injure your eye and notice fuzziness in your central vision, be sure to see your eye doctor immediately.

Inflammation: Inflammatory disease disorders such as cytomegalovirus infection, retinal necrosis, sarcoidosis, Behçet’s syndrome, toxoplasmosis, Eales’ disease, and Vogt-Koyanagi-Harada syndrome are often accompanied by macular edema.

Drugs: History of use of topical epinephrine or prostaglandin drugs for glaucoma.

Surgery: Cataract or other eye surgery

Men are at higher risk

Symptoms of Macular Edema

The symptoms will vary according to how swollen the macula is and whether it is in one or both eyes.

Most people will notice one or more of the following:

• Blurred or wobbly vision
• Vision loss/difficulty reading
• Washed-out colours

If you are struggling with any of these symptoms, see an optometrist as soon as possible. Severe and untreated macular oedema can result in long lasting and severe damage to your eyesight.

Macular Edema Complications

Serious Complications Associated With Macular Edema are as follows:

• Untreated chronic macular edema can lead to permanent damage to the retinal architecture and permanent vision loss.
• Irvine-Gass syndrome, also known as postoperative macular edema, is a common complication of cataract surgery.
• A prior history of diabetes, retinal detachment, ocular inflammation, retinal vein occlusion, epiretinal membrane, and ocular prostaglandin use have all been associated with an increased risk of macular edema after cataract surgery.
• In addition, intraoperative complications during cataract surgery have been associated with a higher incidence of postoperative macular edema.
• The pathogenesis of macular edema after cataract surgery is thought to be multifactorial, but the core mechanism is likely surgically induced inflammation.
• Intraocular inflammation upregulates endogenous inflammatory mediators that increase vasopermeability, leading to the development of macular edema.

Diagnosis and test

To diagnose macular edema, your eye care professional will conduct a thorough eye exam and look for abnormalities in the retina. The following tests may be done to determine the location and extent of the disease:

Visual acuity test: A visual acuity test is a common way to identify vision loss and can help to diagnose vision loss as a result of macular edema. This test uses a standardized chart or card with rows of letters that decrease in size from top to bottom. Covering one eye, you will be asked to read out loud the smallest line of letters that you can see. When done, you will test the other eye.

Dilated eye exam: A dilated eye exam is used to more thoroughly examine the retina. It gives additional information about the condition of the macula and helps detect the presence of blood vessel leakage or cysts. Drops are placed in your eyes to widen, or dilate, your pupils. Your eye care professional then examines your retina for signs of damage or disease.

Fluorescein angiogram: If earlier tests indicate you could have macular edema, your eye care professional may perform a fluorescein angiogram. In this test, a special dye is injected into your arm and a camera takes photos of the retina as the dye travels through the blood vessels. This test helps your ophthalmologist identify the amount of damage to the macula.

Optical coherence tomography: This is a test that uses a special light and a camera for detailed views of the cell layers inside the retina. It detects the thickness of the retina and so it’s useful in determining the amount of swelling in the macula. Your eye care professional may also use optical coherence tomography after your treatment to track how well you are healing.

The Amsler Grid: The Amsler Grid provides an easy way to test whether or not your central vision has changed. It can recognize even small changes in your vision.

The Amsler Grid

If you need reading glasses, wear them when you look at the Amsler grid. The grid should be at the same distance from your eyes as your usual reading material about 14 inches. Test both eyes, one at a time, to see if any parts of the grid look distorted, missing, or dark. Mark the areas of the chart that you’re not seeing properly and bring it with you to your next eye exam.

Macular edema in eye

Treatment and medications

The necessary treatment for macular edema varies for each patient depending on the severity of vision loss, underlying retinal conditions, and how early this condition has been identified.

Patients that have been diagnosed with diabetic retinopathy will notice that there is overlap in treatments. Please click upon the name of the treatment to be redirected to a page with a more detailed description.

Focal Macular Laser Treatment: This laser treatment is used to control bleeding and leakage caused by abnormal blood vessels. During laser treatment, a series of small, painless burns are made to the abnormal blood vessels. This seals the leaks and prevents further bleeding into the retinal.

Avastin or Lucentis Injections: Avastin and Lucentis are both anti-VEGF medications that are injected into the eye. These medications block the chemical responsible for the leakage. Avastin and Lucentis help mitigate the vision loss caused by fluids leaking from these blood vessels.

Periocular and Intravitreal Steroid Injections: Periocular and intravitreal injections of corticosteroids, such as Kenalog, can be used to manage macular edema in conjunction with laser treatment. Regular injections of steroids help to reduce swelling of the macula and leakage of abnormal blood vessels.

Prevention of Macular Edema

• Maintaining good blood sugar, blood pressure, and cholesterol control helps prevent DME.
• Receiving a comprehensive dilated eye exam at least once a year, or more often as directed by the eye doctor.
• Pregnant woman with diabetes should have a comprehensive dilated eye exam as soon as possible. The eye doctor may recommend additional exams during pregnancy.
• Maintaining a healthy lifestyle, exercising regularly, and having a healthy diet. Talk to a doctor before starting an exercise program.