Vascular leakage, fluid, and/or exudate in the macula is referred to as diabetic macular edema (DME). Compare the healthy macula on the left with the edematous macula, caused by leaking microaneurysms, on the right. When diabetic macular edema involves or threatens the fovea, it is termed clinically significant macular edema (CSME). DME is the most frequent cause of moderate visual loss that may occur at any stage of retinopathy, although it is more common and severe in the later stages. It also may be associated with normal vision and may be difficult to appreciate ophthalmoscopically.