Session Title: Imaging III
Session Date/Time: Saturday 19/09/2015 | 16:30-18:00
Paper Time: 16:46
First Author: : J.Costa PORTUGAL
Co Author(s): : J. Marques M. Marques I. Sobral M. Cachulo J. Figueira R. Silva
PURPOSE:To assess the effect of long-standing type 2 diabetes in the morphology of the superficial and deep macular microvascular network using optical coherence tomography-angiography (OCTA).
Department of Ophthalmology, Centro Hospitalar e Universitário de Coimbra (CHUC), Coimbra, Portugal; Association for Innovation and Biomedical Research on Light and Image (AIBILI), Coimbra, Portugal; Faculty of Medicine, University of Coimbra (FMUC), Coimbra, Portugal
Cross-sectional, case-control study, including patients with long-standing type 2 diabetes. Patients with macular edema, significant media opacities or any other ocular comorbidities, were excluded. An age-matched control group was used to establish the standards of a normal OCTA angiogram. All patients underwent a complete ophthalmologic evaluation, followed by OCTA using the AngioVue™ OCTA system (Avanti, Optovue, USA). OCTA data was comprised of 200x200x8 A-scans acquired in 3.5 seconds, containing a 3x3mm area centered on the fovea. The flow was detected using split-spectrum amplitude decorrelation angiography (SSADA), which allows segmentation of the retinal vascular layers. Motion artifacts due to residual axial motion and transverse saccadic motion were automatically removed using the integrated proprietary software. The presence of microvascular abnormalities such as capillary dropout, microaneurysms and neovascularization were evaluated. Additionally, the area and maximal linear diameter of both the superficial and deep foveal avascular zone (FAZ) were manually delineated using ImageJ™. All images were independently classified by two graders.
Twenty-eight eyes of 16 patients, mean-aged 64,19±11.09 years, were included in this study. Average duration of type 2 diabetes mellitus was 18.54±8.85 years. Universal features on the angiograms of diabetic patients included a sparse capillary network with irregular microvessels and perifoveal areas of capillary nonperfusion surrounded by vascular loops. Microvascular changes were more evident in the deep vascular network, where marked areas of capillary dropout and thinning were noted. Microaneurysms were poorly discernible in the 3x3mm scans, regardless of the vascular plexus. No neovascularization was evident in the scanned area. This observation was confirmed by fluorescein angiography. The FAZ was consistently large (>500μm) and irregular, with loss of the usual centripetal arrangement of the bordering vascular network. In all the patients, the deep FAZ was larger than the superficial (0.66mm2 vs 0.41mm2). These results were significantly inferior in the control group, both for the superficial (0.28mm2, p<0.05) and the deep vascular layer (0.38 mm2, p<0.001). Likewise, the maximal linear diameter of the FAZ was notably greater in the outer vascular layers.
OCT-angiography is a novel, non-invasive imaging method that provides detailed, depth-resolved information on the macular vascular network. Descriptive studies on the clinical applications of OCTA are beginning to emerge. In this pioneer study, the vascular changes were particularly noticeable in the deep vascular plexus. This finding is consistent with the microangiopathic nature of diabetic retinopathy. OCTA may provide a different insight into the vascular abnormalities that accompany diabetic retinopathy. Further studies are needed to assess the clinical significance of these preliminary findings.