Optical Coherence Tomography Angiography Findings in Diabetic Patients with Macular Edema

Abstract Background: Diabetic macular edema is one of the most common causes of vision loss in patients with diabetes. Fluorescein Angiography (FA) provides valuable additional information compared to clinical examination or fundus photography but it has many contraindications. It requires venipuncture and intravenous injection of a dye that has a moderate risk of nausea and a rare but well documented risk of anaphylaxis and death. Optical Coherence Tomography Angiography (OCTA) is a non-invasive modality that generates three-dimensional, depth encoded images of blood flow within the eye by using motion contrast. It offers an alternative angiographic technique without the drawbacks of FA. Areas of capillary loss obscured by fluorescein leakage on FA were more clearly defined on OCTA. Aim of Study: To describe the Optical Coherence Tomog-raphy Angiography (OCTA) findings in diabetic patients with macular edema. Patients and Methods: A cross sectional study was carried out on 46 eyes of 30 diabetic patients with macular edema diagnosed by Optical Coherence Tomography (OCT). The findings of the OCT and OCTA were correlated. The presence of microaneurysms and neovascularization was studied in OCTA. Macular perfusion was quantified using OCTA images by 3 parameters: Foveal Avascular Zone (FAZ) area and Vascular Area Density (VAD) at 2 levels; Superficial Capillary Plexus (SCP) and Deep Capillary Plexus (DCP) and Vascular Density Map (VDM). Results: There is a statistically significant difference between the number of microaneurysms in the DCP and SCP (more in the DCP). A significant negative correlation between the duration of hypertension and the vascular area density of superficial capillary plexus. There is a significant difference between eyes with normal and eyes with abnormal inner retinal integrity [Disorganization of the Retinal Inner Layers (DRIL)] as regards the FAZ of superficial and deep capillary plexuses (larger in eyes with DRIL), the vascular area density of superficial capillary plexuses (less in eyes with DRIL) and the vascular density map center 3mm (more in eyes with DRIL). Although one of the strengths of the OCTA is its ability to assess vasculatures and structures of DCP separately from SCP, this is limited by projection artifacts from the superficial structures onto deeper layers. Conclusion: Correlation between OCT and OCTA images is mandatory to explain the OCT and OCTA findings. The presence of microvascular abnormalities, hemorrhages, cotton wool spots and hard exudates gives fallacies in OCTA images interpretation. The significant correlation between the presence of DRIL by OCT and diabetic macular ischemia by OCTA allows for OCT to be sufficient when FFA cannot be done and OCTA is unavailable.