Blood Cell-Derived Inflammatory Indices in Diabetic Macular Edema: Clinical Significance and Prognostic Relevance

Diabetic macular edema (DME) is a leading cause of vision loss in patients with diabetes. While VEGF-driven vascular permeability is central to its pathogenesis, inflammation plays a complementary and pivotal role in disease progression, morphological heterogeneity, and treatment response. Readily available blood cell-derived inflammatory indices, such as the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), monocyte-to-high-density lipoprotein cholesterol ratio (MHR), monocyte-to-lymphocyte ratio (MLR), platelet-to-neutrophil ratio (PNR), and pan-immune-inflammation value (PIV), as well as platelet measures (MPV, PDW), have been investigated as low-cost markers of systemic inflammation in DME. Specifically, comparative studies have reported that an NLR ≥ 2.26 can effectively distinguish DME from non-DME with 85% sensitivity and 74% specificity. Elevated NLR is more associated with serous retinal detachment. Moreover, a baseline NLR ≤ 2.32 has been linked to a better anatomical response to treatment. This narrative review summarizes the evidence regarding these biomarkers' diagnostic and prognostic utility and highlights their associations with OCT morphotypes and anti-VEGF responsiveness. We propose that multi-marker panels integrated with OCT features may enhance risk stratification and help personalize therapy, but emphasize that prospective, multi-center validation and harmonized thresholds are required before routine clinical application.