Nonproliferative Diabetic Retinopathy
SALIENT FEATURES
Nonproliferative diabetic retinopathy (NPDR) is a constellation of retinal changes due to a chronic hyperglycemia-induced microangiography that is staged as mild, moderate, or severe.
Mild NPDR is defined as the presence of at least one microaneurysm.
Eyes that have hard exudates, cotton wool spots, microaneurysms, and intraretinal hemorrhages, but that do not qualify for severe NDPR, are considered moderate NDPR.
Severe NPDR is defined by the “4:2:1: rule,” which is the presence of intraretinal hemorrhage in all four quadrants, venous beading in at least two quadrants, or intraretinal microvascular abnormality (IRMA) in at least one quadrant.
OCT IMAGING
One key role for OCT is the identification of diabetic macular edema (DME). This may include intraretinal fluid and/or subretinal fluid. On OCT, intraretinal fluid consists of hyporeflective cystic spaces within the retina for intraretinal fluid (Figure 5.1, white asterisks). Subretinal fluid consists of hyporeflective fluid beneath the retina and above the retinal pigment epithelium (see Chapter 13).
FIGURE 5.1 Foveal optical coherence tomography (OCT) images from several patients with nonproliferative diabetic retinopathy (NPDR) with and without diabetic macular edema (DME). Microaneuryms are highlighted with yellow arrows. Green arrows indicate hyperreflective dots. Ellipsoid disruption is commonly present and is highlighted by red arrows. White arrows are vitreoretinal abnormalities such as epiretinal membrane, vitreomacular traction/adhesion, and thickened posterior hyaloid. Cystoid macular edema when present is identified with a white asterisk, and focal retinal atrophy is shown in one image with a green asterisk.
Microaneurysms on OCT may be seen as round hyperreflective structures with hyporeflective lumens (Figure 5.1, yellow arrows).
Hard exudates are seen on OCT as small hyperreflective spots 20 to 40 µm in diameter often seen in clusters (Figure 5.1, green arrows). Smaller hyperreflective dots may indicate inflammatory aggregates.1
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