Diabetic Macular Edema

Friday, Nov 1, 2019 by Nisha Gupta, MD

This month we will continue our discussion about diabetes and diabetic eye disease.

We have reviewed the basics about diabetic retinopathy: non-proliferative and proliferative. Now, we will focus on diabetic macular edema (DME).

How is diabetic eye disease in the retina defined?

As we discussed, diabetic retinopathy (DR) and diabetic macular edema (DME) are the retina-related changes in diabetic eye disease. In diabetic retinopathy, the blood vessels of the retina are affected. This is further separated into non-proliferative (NPDR) and proliferative (PDR) disease. PDR is more severe than NPDR.

Diabetic macular edema is a consequence of diabetic retinopathy. It can happen at any stage of retinopathy. It is swelling or a collection of fluid in the center of the retina called the macula.

What puts people at higher risk of developing diabetic macular edema (DME)?

Chronically elevated sugar in the body damages the blood vessels in the retina leading to diabetic retinopathy. This damage to the blood vessels can cause them to leak fluid and lead to the swelling of the macula. The risk also increases with a longer duration of diabetes.

What are the symptoms of DME?

Usually patients have blurry central vision. Distortions or cloudy vision may also occur. Severe or untreated cases can cause vision loss and blindness.

How is it detected?

A comprehensive exam, including checking the vision and dilating the eyes to view the retina, is necessary to detect DME. Photos are taken to diagnose and monitor the disease.

The arrow shows the area of diabetic macular edema.

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Diabetic macular edema. Image Source [^1]

Other photos taken during an exam also help diagnose and monitor DME after treatment. Optical coherence tomography (OCT) shows the layers of the retina that may have fluid. Fluorescein angiography (FA) looks for damaged and leaking blood vessels. FA involves injecting a dye into the arm and taking photos as the dye goes through the blood vessels in the eyes. It will show dye leaking from macular edema if it is present.

This is a normal OCT. The top left photo shows the image of what doctors see during an exam. A map is generated to help see which areas are thicker from the swelling. The two photos under it show cross sections through the macula. The first is a horizontal section, the bottom is a vertical section. The yellow arrows point to a normal area called the fovea. This is where the central vision is concentrated. Disruption to this area will cause blurry vision.

oct normal

Normal OCT. Image Source [^1]

This is an OCT showing diabetic macular edema. The arrows are pointing to the fluid that has disrupted the layers of the retina.

oct dme

OCT with macular edema. Image Source [^1]

This photo is of a normal fluorescein angiogram. The dye lights up as it goes through the blood vessels.

fa normal

Normal FA. Image Source [^1]

This photo is of a patient with diabetic retinopathy and macular edema. The red arrow points to the macular edema. The dye is leaking from the damaged blood vessels and retina layers that are not normal.

fa dme od

FA with macular edema. Image Source [^2]

What are the treatments for diabetic macular edema?

Prevention: Diabetic macular edema is a consequence of diabetic retinopathy. It is very important to get a dilated comprehensive exam once a year to look for changes. If retinopathy and edema are detected, the exams are more frequent.

Controlling sugar, BP, and cholesterol: Studies have shown that maintaining normal sugar levels, blood pressure, and cholesterol reduce the risk of developing eye disease and vision loss. The hemoglobin A1c is used to determine sugar levels over a three-month period. A lower A1c reduces the risk of developing retinopathy.

Lifestyle modifications: Smoking and obesity are risk factors for diabetes and therefore play a role in diabetic eye disease as well.

Injections: Ocular injections are one of the main treatments for macular edema. The medications used are in the class called anti-VEGF medications. VEGF, vascular endothelial growth factor, is a normal compound in the body that regulates the growth of blood vessels. Patients with diabetic retinopathy and macular edema have too much of this compound. The drugs block the effects of VEGF to clear the leaking fluid.

Steroids: Steroids are another class of medications used. There is a component to the macular edema that is caused by inflammation. If the anti-VEGF medications are not working, steroid injections may be given to help clear the fluid.

Laser: There are several types of laser treatments. The one used for DME is lighter than the one used for PDR. It is a targeted laser done in the area of the swelling. The laser involves making small burns in the retina to treat prevent more leaking of fluid. If there is a lot of fluid, doctors may do a combination of injections with laser treatment. They both work together to clear the fluid.

This is the retina after laser treatment. The arrow points to the scars from the laser.

mb focal laser scars

Laser scars. Image Source [^1]

This is the OCT after being treated with laser and injections. The arrows point to the area with less fluid.

oct treated dme

OCT after DME treatment. Image Source [^1]

Low vision tools: There are many aids to help patients with poor vision from diabetic retinopathy and macular edema including magnifiers, high-powered lenses, large print materials, talking clocks and calculators, closed-circuit televisions, and computer-based aids.

Return next month for our final installment of diabetic eye disease!

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