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Nonproliferative Diabetic Retinopathy And Macular Edema

The earliest retinal changes of diabetic retinopathy are called non–proliferative or background diabetic retinopathy and result from damage to the small blood vessels in the retina. At first these vessels may begin to bleed and leak fluid into the surrounding retinal tissue. In the earliest stages of this condition, the patients usually have no symptoms and have 20/20 vision. A qualified practitioner, such as a general ophthalmologist or retinal specialist, may detect these changes by performing a dilated eye examination.

This color retinal photograph demonstrates nonproliferative diabetic retinopathy. The image is centered on the macula (the part of the retina responsible for central fine vision) with part of the optic nerve seen on the left of the photo

This color retinal photograph demonstrates nonproliferative diabetic retinopathy. The image is centered on the macula (the part of the retina responsible for central fine vision) with part of the optic nerve seen on the left of the photo (left eye). There are hemorrhages within the retinal tissue on the right side of the photograph. (Click image for full size image.)

The doctor looks for small spots of bleeding or areas of retinal swelling due to fluid leakage. Sometimes, fatty material leaks from damaged vessels and collects in the retina as deposits called exudates. The ophthalmologist will often take color photos of the back of the eye to document the retinal changes. Non–proliferative diabetic retinopathy is further sub–divided into mild, moderate, and severe depending on the number and amounts of bleeding and leaking areas.

Frequently, especially if there is reduced vision, the ophthalmologist may elect to investigate the retinal changes further with a special diagnostic test know as a fluorescein angiogram. This test involves injecting a yellow dye into an arm vein and photographing the back of the eye as the dye passes through the retinal circulation. This test is especially useful for identifying areas of blood vessel damage and abnormal leakage from them. The test does not involve the use of X–rays. Patients should be aware that their urine will be bright yellow for a day or two following the injection.

This fluorescein angiogram shows the retinal vessels are filled with the fluorescent dye.

Fluorescein angiogram of the same patient shown above. The retinal vessels are filled with the fluorescent dye. Hemorrhages appear as dark spots in the angiogram and correspond to those seen in the color photo. On the right side of the image, there is damage to retinal blood vessels which no longer fill with the dye. This is called an area of non–perfusion, also called retinal ischemia.

Optical Coherence Tomography (OCT) is another test that is commonly obtained in order to assess fluid accumulation (macular edema) in the retina in patients with diabetes. OCT can demonstrate areas of retinal thickening and can be a useful tool in assessing a patients response to a treatment.

Normal cptical coherence tomography (OCT) demonstrating normal retinal contour

Normal OCT demonstrating normal retinal contour. (Click image for full size image.)

Macular Edema

In some cases of non–proliferative diabetic retinopathy, enough leakage may occur in the retina to cause it to become swollen with fluid. This condition is called diabetic macular edema. Macular edema is the most common cause of vision loss in patients with diabetes, occurring in upwards of 10% of all diabetic patients. Patients with diabetic macular edema experience reduced vision in the form of blurring, darkening or distorted images. Often the amount of retinal and macular edema, and associated symptoms, will be unequal between the two eyes.

Color retinal photograph demonstrating diabetic macular edema. The image is centered on the macula with the optic nerve seen on the right.

Color retinal photograph demonstrating diabetic macular edema. The image is centered on the macula with the optic nerve seen on the right of the photo (right eye). The macula is swollen with fluid. There are white fatty deposits in the retina (exudates) which are frequently seen in such cases.

Fluorescein angiogram of the same patient illustrated above. The test pinpoints the areas of leakage and helps determine its severity.

Fluorescein angiogram of the same patient illustrated above. The test pinpoints the areas of leakage and helps determine its severity. Fluorescein angiography helps the ophthalmologist determine whether laser treatment is indicated. It also helps in targeting the proper areas for treatment.

Optical Coherence Tomography of a patient with diabetic macular edema. The retinal layers are swollen.

OCT of a patient with diabetic macular edema. The retinal layers are swollen.

The treatment of diabetic macular edema is rapidly evolving. Treatment options include focal laser photocoagulation and intraocular injections of steroids or other medications. These treatments are reviewed in detail in the section “Treatment Options for Diabetic Retinopathy”.