There are specific neural and microvascular modifications even before clinical signs of diabetic retinopathy in DM Types 1 and 2. Perifoveal capillary loss in the SCP is highly correlated with inner retinal layer. These data may help in characterization of patients at the preclinical stage of diabetic retinopathy.

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PURPOSE. To evaluate peripapillary vessel density and morphology in patients with diabetes mellitus (DM) without clinical signs of diabetic retinopathy (DR) and with mild, nonproliferative DR and to correlate with peripapillary nerve fiber layer (NFL) thickness. METHODS. One hundred seventeen eyes (34 healthy controls, 54 patients with DM without DR [noDR group] and 24 patients with mild DR [DR group]) were prospectively evaluated. All subjects underwent peripapillary and macular optical coherence tomography angiography (OCT-A). Peripapillary NFL thickness was also recorded. OCT-A slab of radial peripapillary plexus (RPC) and macular superficial capillary plexus (SCP) were analysed in order to calculate perfusion density (PD) and vessel density (VD). Further an image analysis of RPC slab was performed to identify number of branches (NoB) and total branches length (tBL). RESULTS. In peripapillary area there was a significant decrease in VD (P ¼ 0.003), NoB (P < 0.001), and tBL (P < 0.001) in noDR group versus controls; PD values were not different among groups (P ¼ 0.126); there was a significant decrease in average NFL thickness in DR versus controls (P ¼ 0.008) and in the inferior quadrant in noDR group versus controls (P ¼ 0.03); there was a significant correlation between OCT-A and NFL thickness values (q ranging from 0.19-0.57). In macular region PD and VD were decreased only in DR group (P < 0.05). CONCLUSIONS. There are early changes in the peripapillary vessel morphology and VD of the RPC in patients with DM without DR that correlate to NFL thinning. Earlier changes in superficial vessel density are documented in the peripapillary than in the macular region. These data may confirm a coexistence of an early neuronal and microvascular damage in patients with DM without clinical signs of DR.

Purpose: To assess changes on optical coherence tomography (OCT) angiography in diabetic macular edema (DME) treated with subthreshold micropulse yellow laser (SMPL) over a period of 6 months. Methods: Thirty-five eyes (35 consecutive patients) with treatment-naive DME prospectively underwent (at baseline, 3 and 6 months) best-corrected visual acuity, swept-source OCT angiography/OCT, and fundus autofluorescence. Following parameters were evaluated on OCT angiography in the superficial capillary plexus (SCP) and deep capillary plexus (DCP): the area of foveal avascular zone, number of microaneurysms (MA), area of cysts, and presence of capillary network alterations. Microaneurysm change was also evaluated in 15 fellow eyes, not needing treatment over 6 months. Vessel and perfusion densities were evaluated in the SCP, DCP, and choriocapillaris, with image J. Retina thickness, number of hyperreflective retinal spots, and external limiting membrane integrity were evaluated on OCT. All measurements were performed by two masked graders, independently. Results: All patients had diabetes mellitus Type 2 (mean age, 69.4 ± 10.9 years; duration of diabetes mellitus, 15.7 ± 8.7 years; and HbA1c 7.7 ± 1.2%). Mean best-corrected visual acuity at baseline was 69.7 ± 12.0 letters ETDRS, 72.7 ± 10.7 at 3 months (gain 3.1 ± 4.3, P = 0.0049) and 74.3 ± 9.5 at 6 months (gain 4.6 ± 7.2, P < 0.0001). Foveal avascular zone area decreased in the DCP at 6 months (P = 0.01). Area of cysts decreased in the SCP at 3 months and 6 months (P = 0.038; P = 0.049), and in the DCP at 6 months (P = 0.0071). Number of MA decreased at 6 months in the SCP (P = 0.0007) and at 3 months and 6 months in the DCP (P = 0.048; P < 0.0001) in treated eyes. No significant change in number of MA was found in nontreated eyes. There was no statistically significant change in any other OCT angiography/OCT parameter. Conclusion: Subthreshold micropulse yellow laser induces more pronounced changes in the DCP than in the SCP in DME. These changes occurred as early as 3 months after treatment. The evaluation of specific parameters in the DCP may help in determining treatment response.

Optical coherence tomography angiography (OCT-A) has recently improved the ability to detect subclinical and early clinically visible microvascular changes occurring in patients with diabetes mellitus (DM). The aim of the present study is to evaluate and compare early quantitative changes of macular perfusion parameters in patients with DM without DR and with mild nonproliferative DR (NPDR) evaluated by two different swept-source (SS) OCT-A instruments using two scan protocols (3×3 mm and 6×6 mm). One hundred eleven subjects/eyes were prospectively evaluated: 18 healthy controls (control group), 73 eyes with DM but no DR (no-DR group), and 20 eyes with mild NPDR (DR group). All quantitative analyses were performed using ImageJ and included vessel and perfusion density, area and circularity index of the FAZ, and vascular complexity parameters. The agreement between methods was assessed according to the method of Bland-Altman. A significant decrease in the majority of the considered parameters was found in the DR group versus the controls with both instruments. The results of Bland-Altman analysis showed the presence of a systemic bias between the two instruments with PLEX Elite providing higher values for the majority of the tested parameters when considering 6×6 mm angiocubes and a less definite difference in 3×3 mm angiocubes. In conclusion, this study documents early microvascular changes occurring in the macular region of patients at initial stages of DR, confirmed with both SS OCT-A instruments. The fact that early microvascular alterations could not be detected with one instrument does not necessarily mean that these alterations are not actually present, but this could be an intrinsic limitation of the device itself. Further, larger longitudinal studies are needed to better understand microvascular damage at very early stages of diabetic retinal disease and to define the strengths and weaknesses of different OCT-A devices.