Regional Variety of Reduction in Retinal Thickness of Diabetic Macular Edema after Anti-VEGF Treatment.

Background and Objectives: The presence of refractory cases resistant to anti-vascular endothelial growth factor (VEGF) therapy for diabetic macular edema (DME) is a problem in clinical practice. This study aimed to explore the less responsive area of optical coherence tomography (OCT) 3D map the characteristics of naïve DME cases after their first anti-VEGF. Materials and Methods: In 46 patients with DME who received an intravitreal injection of anti-VEGF agents, retinal thickness in 100 sections of the macular area was measured by 3D-mapping mode using OCT before and 1 month after injection. The density of the microaneurysm (MA) was calculated using merged images of the OCT map and fluorescein angiography. Results: One month after injection, the central retinal thickness significantly decreased (p < 0.0001). In severe edema (retinal thickness more than 500 µm), the area percentages with a reduction rate of the retinal thickness greater than 30% and less than 5% were 6.4 ± 6.6% and 10.1 ± 4.6%, respectively. The reduction rate of the retinal thickness varied from section to section. The mutual distance between the areas of maximum thickness before and after the injection averaged 1.22 ± 0.62 mm apart. The reduction rate of retinal thickness in the thickest region before injection was significantly higher (p = 0.02), and that in the thickest region after injection was lower (p = 0.001) than in the other regions. MA density in the residual edema was significantly higher than in the edema-absorbed area (p = 0.03). Conclusion: DME has areas that show low response to the reduction in retinal thickness with anti-VEGF therapy. A high density of MA may be associated with this pathogenesis.