Purpose The purpose of this study was to evaluate differences in optical coherence tomography angiography (OCTA) metrics in the superficial (SCP), intermediate (ICP), and deep (DCP) vascular plexuses across diabetic retinopathy (DR) severity levels. Methods This was a cross sectional observational retrospective chart review study. Eligible patients with diabetes who underwent same day RTVue XR Avanti OCTA, spectral-domain optical coherence tomography (SD-OCT), and 200-degree Optos ultrawide field color imaging. SCP, ICP, and DCP vessel density (VD) and vessel length density (VLD) were assessed using 3-D projection artifact removal software (PAROCTA) software. Results Of 396 eyes (237 patients), 16.1% had no DR, 26.9% mild nonproliferative DR (NPDR), 21.1% moderate NPDR, 12.1% severe NPDR, 10.1% proliferative DR (PDR) without panretinal photocoagulation (PRP), and 13.4% PDR with PRP. When comparing mild NPDR to no DR eyes, ICP and DCP VD and VLD were significantly lower, but there was no difference for SCP metrics. In eyes with more severe DR, there were significant differences in SCP VD and VLD between DR severity levels (mild versus moderate NPDR: VD 35.45 ± 3.31 vs. 34.14 ± 3.38, P = 0.008 and VLD 17.59 ± 1.83 vs. 16.80 ± 1.83, P = 0.003; moderate versus severe NPDR: VLD 16.80 ± 1.83 vs. 15.79 ± 1.84, P = 0.019), but no significant differences in ICP or DCP. Conclusions Although VD of each of the three individual layers decreases with increasing DR severity, DR severity has a substantially different effect on OCTA parameters within each layer. Vascular changes in eyes with no to early DR were present primarily in the deeper vascular layers, whereas in eyes with advanced DR the opposite was observed. This study highlights the effects of ICP and the importance of assessing SCP and DCP changes independently across each DR severity level.

Diabetic retinopathy (DR) is a leading cause of vision loss worldwide. Microaneurysms (MAs), which are abnormal outpouchings of the retinal vessels, are early and hallmark lesions of DR. The presence and severity of MAs are utilized to determine overall DR severity. In addition, MAs can directly contribute to retinal neural pathology by leaking fluid into the surrounding retina, causing abnormal central retinal thickening and thereby frequently leading to vision loss. Vascular perfusion parameters such as shear rate (SR) or wall shear stress (WSS) have been linked to blood clotting and endothelial cell dysfunction, respectively in non-retinal vasculature. However, despite the importance of MAs as a key aspect of diabetic retinal pathology, much remains unknown as to how structural characteristics of individual MAs are associated with these perfusion attributes. MA structural information obtained on high resolution adaptive optics scanning laser ophthalmoscopy (AOSLO) was utilized to estimate perfusion parameters through Computational Fluid Dynamics (CFD) analysis of the AOSLO images. The HemeLB flow solver was used to simulate steady-state and time-dependent fluid flow using both commodity hospital-based and high performance computing resources, depending on the degree of detail required in the simulations. Our results indicate that WSS is lowest in MA regions furthest away from the feeding vessels. Furthermore, areas of low SR are associated with clot location in saccular MAs. These findings suggest that morphology and CFD estimation of perfusion parameters may be useful tools for determining the likelihood of clot presence in individual diabetic MAs.

Purpose The purpose of this study was to assess how projection artifact removal (PAR) alters optical coherence tomography angiography (OCTA) assessment of superficial capillary plexus (SCP) and deep capillary plexus (DCP) in eyes of patients with diabetes. Methods We acquired 3 × 3 mm scans with RTVue-XR Avanti (Optovue, Inc., Fremont, CA), which were analyzed with PAR software (PAROCTA) and without (non-PAROCTA). SCP, DCP, and full thickness retina vascular density (VD) and vessel linear density (VLD) were manually calculated using ImageJ (version 1.51). Adjusted flow index (AFI) was manually assessed for full thickness images. Results Among 323 eyes of 194 patients (no diabetic retinopathy [DR]: 28 eyes; mild nonproliferative DR (NPDR): 96 eyes; moderate: 82 eyes; severe: 32 eyes; and proliferative DR [PDR]: 81 eyes), SCP VD and VLD were lower with PAROCTA than with non-PAROCTA only in eyes with moderate (VD: P = 0.017; VLD: P = 0.046), severe ( P = 0.016; P = 0.009), and PDR ( P < 0.001; P = 0.002). DCP VD and VLD were higher with PAROCTA as compared to non-PAROCTA only in eyes with no DR (VD and VLD: P < 0.001), mild (VD and VLD: P < 0.001), moderate (VD: P = 0.005; and VLD: P < 0.001), and severe (VD: P = 0.009; VLD: P < 0.001). Full thickness PAROCTA and non-PAROCTA VD and VLD differed only in eyes with no DR where PAROCTA estimates were higher (VD: P = 0.009; VLD: P = 0.02). PAROCTA AFI was lower than non-PAROCTA AFI for all DR severity levels ( P < 0.001) except no DR. Conclusions Although differential effects of PAROCTA software are expected on SCP versus DCP measurements, these findings also suggest an interaction between PAROCTA and DR severity on assessment of VD. Conclusions from previous studies that have not corrected VD with PAR software should be carefully reviewed with regard to the role of specific vascular layers in DR. Translational Relevance Previous OCTA studies that have not corrected VD with PAR software should be carefully reviewed with regard to the role of individual vascular layers in differing severity levels of DR.

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Précis: Myopic glaucoma suspects, particularly with high myopia, experience thinning of nontemporal parameters of retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL), without change in optic nerve head (ONH) parameters. Purpose:The aim was to assess the effect of myopia on RNFL, GCIPL, and ONH parameters in glaucoma suspects.Materials and Methods: Seventy-six eyes of glaucoma suspects studied with Cirrus high definition optical coherence tomography were divided into low (n = 27), moderate (n = 25), and high myopia (n = 24) groups. Optical coherence tomography parameters were correlated with spherical equivalent (SE) and evaluated with areas under the receiver operating characteristic curve for quantifying diagnostic ability to differentiate high myopia from nonhigh myopia.Results: In high myopia, SE was positively correlated with thinning of average, minimum, and nontemporal GCIPL and thinning of average and nontemporal RNFL (P < 0.05 for all), but not for inferior RNFL (P = 0.28). In moderate myopia, SE was correlated with thinning of inferonasal and minimum GCIPL as well as superior and inferior RNFL (P < 0.05 for all). SE was not correlated with ONH parameters in moderate or high myopia (P > 0.05). The largest areas under the receiver operating characteristic curve for RNFL and GCIPL parameters were for superior (0.82) and superonasal (0.80) regions, respectively, with comparable diagnostic ability (P = 0.74). Conclusion:High myopia, in particular, is associated with thinning of average RNFL, average and minimum GCIPL, and nontemporal parameters of both RNFL and GCIPL, warranting consideration of refractive status in glaucoma suspects.