DME is currently diagnosed by slit-lamp biomicroscopy and optical coherence tomography (OCT). Conventionally, OCT is used to assess edema (retinal thickening and fluid pockets). The initial assessment and treatment planning also requires an assessment of macular perfusion, which is currently done by fluorescein angiography (FA). FA is used to identify microaneurysms and areas of capillary dropout (ischemia), which guides focal laser treatment and helps predict treatment response. Eyes with greater ischemia respond more poorly to treatment. FA requires the injection of sodium fluorescein into the systemic circulation. However, 1 in 3 people have adverse reactions to sodium fluorescein, which can include nausea, vomiting, hives, and acute hypotension. Severe reactions such as anaphylaxis, causing cardiac arrest and sudden death due to anaphylactic shock, have also been reported. Finally, because the risks of sodium fluorescein to a developing fetus are unknown, its use in pregnant women is contraindicated. Replacing FA with a less invasive and better tolerated method would reduce the risk in the patient population. One option is OCT angiography.