There is strong evidence to indicate that prevention of non-central involved DME from progression into the central subfield of the macula is a good anatomic surrogate for preventing visual acuity loss. Furthermore, the prevalence of macular edema is estimated to be high among patients with diabetes, and it is likely that approximately 25% of non-central involved cases of DME extend into the central subfield of the macula within one year. Thus, if a relatively safe and economical treatment could be identified that reduced the progression of non-central involved edema to central-involved edema by at least 50%, this treatment could have a major public health impact.