Optical Coherence Tomography Biomarkers as Potential Predictors for Visual Function and Response to Intravitreal Therapy in Diabetic Macular Edema

Purpose: To synthesize a broad range of optical coherence tomography (OCT) biomarkers in diabetic macular edema (DME) and their associations with visual acuity (VA) and response to intravitreal antivascular endothelial growth factor (anti-VEGF) and corticosteroid therapy. Methods: A literature review was conducted. Results: Disorganization of the inner retinal layers (DRIL), presence of epiretinal membrane (ERM), ellipsoid zone (EZ) integrity, and external limiting membrane (ELM) continuity were the most commonly reported biomarkers. In most studies, absence of baseline DRIL/ERM, as well as preserved ELM/EZ continuity, was associated with a better final VA and improved response to intravitreal injections (IVI). Lower choroidal vascularity index was associated with a favorable response to anti-VEGF therapy and a poorer response to corticosteroids. Studies reporting hyperreflective dots showed mixed results. Degradation of the retinal pigment epithelium (RPE), increased central retinal thickness (CRT), and foveal eversion were associated with poor visual outcomes and poor response to both anti-VEGF and corticosteroid IVI. Conclusions: Although many studies reported similar trends in biomarker levels after anti-VEGF and corticosteroid IVI, certain biomarkers (DRIL, hyperreflective dots, and CRT) were found to be more responsive to global cytokine suppression using corticosteroids than anti-VEGF agents. The absence of DRIL and preserved EZ/ELM correlated with improved visual outcomes. However, data concerning the choroidal vascularity index, RPE continuity, CRT, and hyperreflective dots are relatively limited. Future prospective studies that focus on these biomarkers, as well as the ongoing advancements in OCT imaging and the integration of artificial intelligence, will help to individualize treatment strategies for patients with DME.