• Diabetic macular edema (DME) is a relatively common vision problem in people with diabetes.
• Optical coherence tomography (OCT) is a type of scan an eye doctor uses to diagnose DME.
• Early detection and treatment of DME can prevent blindness.

Although taking care of your vision may not seem like a top priority when managing type 2 diabetes, it is. Vision problems that can lead to blindness are a common complication of diabetes. When they’re caught early, however, they’re often treatable. Regular eye exams and imaging tests such as optical coherence tomography can help ensure that eye problems such as diabetic macular edema are detected and treated as soon as possible.

If you or a loved one is living with type 2 diabetes, it’s essential to talk to a health care professional about risks associated with developing DME and how optical coherence tomography can help detect it. Ultimately, yearly checkups with an ophthalmologist (eye doctor) can help protect eye health and prevent vision loss.

What Is Diabetic Macular Edema?

Diabetic macular edema is an eye disease caused by diabetes. The macula is part of the eye responsible for focusing on details directly in front of you, like reading text or recognizing faces. It’s located at the back of the eye in a layer of tissue called the retina. The retina processes all of your visual surroundings, which includes your direct line of focus and everything in the periphery (outer edges of your vision). The word “edema” means “swelling,” and macular edema is swelling of the macula.

DME is a relatively common eye condition in those with diabetes. Up to 7 percent of people with diabetes develop DME. Blurred vision is a common symptom of DME. One DiabetesTeam member shared, “When my blood sugar is high, my vision can be blurry.”

Other symptoms of DME include:

• Floaters — Spots that float around in your vision
• Wavy vision
• Light sensitivity
• Headaches
• Trouble focusing and reading

Another DiabetesTeam member described their experience with floaters: “I have a bubble type of floater that appears in my eye. It floats across my line of sight.”

More than 50 percent of people with diabetes develop diabetic retinopathy, a condition where high blood glucose damages the small capillaries (blood vessels) in the retina. These damaged vessels leak fluids, fats, and inflammatory chemicals like vascular endothelial growth factor (VEGF), which promote the growth of new, abnormal blood vessels. This leakage can cause DME, leading to swelling and thickening of the retina and macula. When fats aren’t cleared, they bond and form hard exudates, small yellowish deposits that leak from damaged blood vessels in the eye. These deposits can build up in the retina, blocking light and affecting visual clarity.

What Is Optical Coherence Tomography?

Optical coherence tomography is the cornerstone for diagnosing and monitoring DME. OCT uses a machine to measure and map retinal, macular, and optic nerve thickness. Using a laser with near-infrared (long wavelength) light, OCT uses a light beam to produce high-resolution 3D images of your retina. This type of imaging technology is used to diagnose other retinal diseases such as age-related macular degeneration (AMD) and glaucoma. It’s also used in other types of medicine such as cardiology, dentistry, oncology, and gastroenterology.

Images produced by OCT can show highly detailed cross-sections and layers of the eye’s retina and optic nerve.

Limitations of Optical Coherence Tomography

OCT may not be effective for people with cataracts, which cause the lens of the eye to become cloudy. Normally, the lens in the eye is clear, allowing light to enter and focus on the retina. A cataract can blur the light used for OCT imaging.

Diabetic retinopathy can cause bleeding in the back side of the eye, known as vitreous hemorrhage, which can also hamper the image quality of OCT testing.

Diagnosing DME With Optical Coherence Tomography

OCT is a painless, noninvasive technology, meaning nothing is inserted into the eye. During an OCT scan, your doctor may or may not use eye drops to dilate your pupils to allow more light to enter. You’ll rest your chin on the OCT machine to keep your head still. Your eyes will be focused on a fixed point while the machine takes a series of pictures of your retina. Each eye will be imaged individually. The test usually takes 5 to 10 minutes. If your eyes have been dilated, they may be light sensitive for a few hours after your exam.

In people with DME, the layers of the retina are abnormally thick due to swelling from fluid build-up. OCT can detect macular swelling and other structural changes that may develop with DME. For instance, OCT scanning can detect retinal disorganization, which causes changes in the layers of cells in the retina.

OCT can also determine whether you have center-involved or non-center-involved DME. In center-involved DME, there is swelling in the fovea (center of the macula), which affects central vision — the ability to focus on objects in front of you. Non-center-involved DME means that the swelling is outside of the fovea.

OCT is also used to monitor how DME treatment is working.

Optical Coherence Tomography Angiography

Sometimes in DME and diabetic retinopathy, the capillaries in the eye start to grow more than they should. Ophthalmologists can use optical coherence tomography angiography (OCTA) — a slightly different imaging test — to take detailed pictures of blood vessels that are both in and under the retina. OTCA can help your doctor see if there are additional capillaries. It can also show any abnormal changes in the blood vessels or signs of leakage.

OCTA is similar to fluorescein angiography, in which a dye is injected into a vein in the arm. The dye travels to the retina and then pictures of retinal blood vessels are taken. OCTA doesn’t require a dye and is a quicker test.

Talk to Your Doctor

If you have diabetes and are having problems with your eyesight, talk to your health care provider or ophthalmology team. Health experts generally recommend that people with diabetes follow up with an eye care specialist every year to check for retina damage and vision impairment.

Diagnosing DME early is important, as effective treatments are available to prevent vision loss. If you are diagnosed with DME, your doctor will discuss treatment options with you, including changes in lifestyle, corticosteroids (steroids), and anti-VEGF treatment.

Find Your Team

DiabetesTeam is the social network for people with diabetes and their loved ones. On DiabetesTeam, more than 158,000 members come together to ask questions, give advice, and share their stories with others who understand life with diabetes.

Do you have DME or diabetic retinopathy? Did your diagnosis involve an OCT scan? Share your experience in the comments below, or start a conversation by posting on your Activities page.