Characteristics of Microaneurysm Size in Residual Edema After Intravitreal Injection of Faricimab for Diabetic Macular Edema

<b>Background/Objectives:</b> Microaneurysms (MAs) are important in the pathology of diabetic macular edema (DME) and its response to anti-vascular endothelial growth factor (VEGF) therapy. This study aimed to clarify the morphological characteristics of MAs in residual edema following consecutive faricimab injections, a bispecific antibody against angiopoietin-2 and VEGF. <b>Methods:</b> We selected patients with DME who exhibited residual edema after three monthly injections of faricimab. In both the residual and absorbed areas of edema, we counted the turnover of MAs, including those that were lost and those that were newly formed. The total number of MAs was determined based on the merged images from an optical coherence tomography (OCT) map and fluorescein angiography. <b>Results:</b> A total of 8 of the 42 patients who received three monthly injections of faricimab showed residual edema one month after the injections. In the residual edema, the density of MAs and the number of maintained MAs were significantly higher (<i>p</i> = 0.04), while the number of disappeared MAs (<i>p</i> = 0.04) and MA turnover (<i>p</i> = 0.01) were lower compared to the absorbed areas. Among the MAs that persisted after the initial injection, the proportion of large-sized MAs (<i>p</i> = 0.01) and their density were significantly greater than those in the absorbed area. In conclusion, the residual areas following three doses of faricimab displayed a higher MA density, less MA loss, and a high density of large-sized MAs compared to the absorbed areas. Our data suggest that large-size MAs located in the residual edema are characteristic of DME cases refractory to faricimab treatment.