Normative data on the foveal avascular zone in a young healthy Irish population using optical coherence tomography angiography

Purpose To establish normative data on the size, shape and vascular profile of the foveal avascular zone (FAZ) in a young, healthy, Irish population, using the Cirrus 5000 HD-OCT. Certain diseases may alter FAZ appearance. Normative databases provide normal baseline values for comparison, thus improving diagnostic ability. Methods One hundred and fifty-four subjects aged 18–35 years old were recruited. Superficial FAZ area, diameter, circularity, ganglion cell layer, central macular thickness (CMT), vascular perfusion and density were measured using the Cirrus 5000. Axial length was measured with the IOL Master and blood pressure was measured using the Omron sphygmomanometer. Results Mean FAZ area was 0.22 ± 0.07 mm2, mean CMT was 263.08 ± 18.73μm. Both were larger in females than males (p = 0.022, p = 0.000). Mean vessel density and perfusion central were 14.11 ± 2.77 mm/mm2 and 24.70 ± 4.96% respectively. Both were lower in females (p = 0.010, p = 0.019). Vessel density and perfusion inner correlated positively with minimum ganglion cell layer plus inner plexiform layer (GCL + IPL) thickness (p = 0.001, p = 0.019). CMT correlated positively with vessel density and perfusion central (p = 0.000 for both) and negatively with FAZ area (p = 0.000). Conclusions This study provides normative data for FAZ appearance and vascularity for the first time in a young, healthy, Irish population, using the Cirrus 5000 HD-OCT. Establishing machine and population specific normative data, particularly in relation to vessel density and perfusion is paramount to the early identification of ocular disease using Optical Coherence Tomography Angiography.

Compensatory contribution of retinal larger vessels to perfusion density in diabetics without retinopathy

Vessel and perfusion densities may decrease before diabetic retinopathy appears; it is unknown whether these changes affect the contribution of vessel density to perfusion density. This was a non-experimental, comparative, prospective, cross-sectional study in non-diabetic subjects (group 1) and diabetics without retinopathy (group 2). Vessel and perfusion densities in the superficial capillary plexus were compared between groups at the center, inner, and full regions and by field (superior, temporal, inferior, nasal) using optical coherence tomography angiography. Coefficients of determination (R2) between vessel and perfusion densities were calculated to find the contribution of larger retinal vessels to perfusion density. Percent differences were used to evaluate the contribution of these vessels to perfusion density in a regression model. There were 62 participants, 31 eyes by group; vessel and perfusion densities as well as the coefficients of determination between them were lower in group 2, especially in the nasal field (R2 0.85 vs. 0.71), which showed a higher contribution of larger retinal vessels to perfusion density. The regression model adjusted to a quadratic equation. In diabetics without retinopathy the contribution of vessel density to perfusion density may decrease; a low vessel density may increase the contribution of larger retinal vessels to perfusion density.

Rapid Patient-Side Evaluation of Endothelial Glycocalyx Thickness in Healthy Sedated Cats Using GlycoCheck® Software

The endothelial glycocalyx (EG) determines transvascular fluid fluxes, and influences inflammation, coagulation, and capillary blood flow. The GlycoCheck® software calculates EG thickness using sidestream dark field videomicroscopy recordings. This method has not been evaluated for use in cats. The aim of the present study was to evaluate the use of GlycoCheck® for estimating EG thickness in healthy cats, and to investigate the variability of EG thickness in this population. One hundred and one healthy research-purposed cats were included in the study. The cats were sedated, and a handheld videomicroscope, connected to GlycoCheck® software, was used to evaluate the sublingual microvasculature. The parameters measured included perfused boundary region (PBR, an indirect measurement of EG thickness) in vessels between 5 and 25 μm in diameter, valid vessel density, percentage red blood cell filling, and median red blood cell column width. Heart rate, respiratory rate, pulse oximetry and oscillometric blood pressure readings were also recorded. There were 35 neutered male cats, 11 intact males, 38 neutered females, and 17 intact females. The average age was 63 months (range, 11–160 months). Tolerance intervals for PBR (vessel diameter 5–25 μm) were 1.89–3.00 μm (95% CI, lower limit 1.76–2.04, upper limit 2.83–3.13 μm); for valid vessel density were 73.33–333.33 μm/mm2 (95% CI, lower limit 77.00–99.33, upper limit 312.67–350.33 μm/mm2); for percentage red blood cell filling were 59.85–85.07% (95% CI, lower limit 58.97–63.33, upper limit 83.07–88.20 %); and for median red blood cell column width were 5.63–8.59 μm (95% CI, lower limit 5.28–6.07, upper limit 8.14–9.51 μm). There was a negative association between median red blood cell column width and body weight (p = 0.007). The median red blood cell column was significantly wider in intact females when compared to spayed females (p = 0.033). The GlycoCheck® analysis was easily performed in healthy sedated cats. Clinical variables did not have an effect on the EG thickness. These results suggest that this technique could be valuable for evaluation of the EG and microvascular parameters in cats.

Persistent reduction of retinal microvascular vessel density in patients with moderate and severe COVID-19 disease

ObjectiveThis study aims to analyse the possible recovery or worsening in retinal microvasculature after 8 months in a previously studied COVID-19 cohort.Methods and analysisA cross-sectional case–control study and a prospective longitudinal cohort study. Participants were the subjects of our previous study who re-enrolled for a new examination including a fundus photograph (retinography), an optical coherence tomography (OCT) scan and an OCT angiography. COVID-19 diagnosed patients were divided into three groups: group 1: mild disease, asymptomatic/paucisymptomatic subjects who received outpatient care; group 2: moderate disease and group 3: severe disease, both of which required hospital admission because of pneumonia. Statistical analyses were performed using SPSS software (V.23.0). Cross-sectional intergroup differences were analysed by means of analysis of variance for normally distributed variables and the Kruskal-Wallis test for non-normally distributed ones. In reference to the prospective part of the study (intragroup differences, baseline with 8-month comparison), a paired t-test was used for normally distributed data and Wilcoxon signed ranks sum for non-normally distributed data.ResultsThe fovea-centered superficial and deep vascular densities were significantly diminished in severe cases compared with mild cases (p=0.004; p=0.003, respectively, for superficial and deep) and to controls (p=0.014; p=0.010), also in moderate cases to mild group (p=0.004; p=0.003) and to controls (p=0.012; p=0.024). In the longitudinal study, no significant statistical differences were found between baseline and 8-month follow-up vessel density values.ConclusionWe demonstrated persistent reduction in the central vascular area over time in patients with moderate and severe COVID-19.

Beetroot juice: effects on blood pressure, intraocular pressure, and ocular vessel density in healthy adults

Background: The blood pressure (BP)-lowering effect of beetroot is attributed to its high nitrate concentration, which converts to the vasodilator nitric oxide. Nitric oxide may also mediate ocular aqueous outflow to regulate intraocular pressure (IOP). Aims: We investigated the effect of beetroot juice on IOP and ocular vessel density. Subjects and Methods: With a single-blind, crossover design, 19 healthy young adults participated on 2 days 1 week apart. On Visit 1, baseline IOP, BP, and ocular vessel density (optical coherence tomography angiography, disc, and macula) were measured. Three hours after consumption of 16 ounces of beetroot juice or water (randomly assigned), all measurements were repeated. On Visit 2, baseline and 3-hour post-consumption measurements were assessed, with each subject consuming the drink not ingested on Visit 1. Results: Paired-samples t-test showed 1) no difference in IOP change post-water vs post-beet root juice (P = 0.27), and 2) mean systolic and diastolic BPs were lower only post-beet root juice (systolic: -4.8 (SEM ± 2.1) mm Hg, P = 0.032, 95% CI (0.47, 9.11); diastolic: -6.2 (SEM± 1.4) mm Hg, P <0.001, 95% CI (3.27, 9.15)). Superficial vessel density was significantly lower in several macular regions post-beet root juice, but not post-water (Wilcoxon signed ranks test, immediately superior, inferior, and temporal to center; respective P values of 0.016, 0.035, and 0.046). Conclusions: Beetroot juice lowers BP and macular vessel density, but does not lower IOP in young, healthy adults. Further investigation into its effect on IOP and vessel density in glaucomatous eyes is warranted. Keywords: beetroot, blood pressure, intraocular pressure, vessel density.

Outer Macular Microvascular Supply in Retinitis Pigmentosa Examined using Optical Coherence Tomography Angiography

Purpose. To determine the vessel density of the superior (SCP) and deep retinal capillary plexuses (DCP) in patients with retinitis pigmentosa (RP) using optical coherence tomography angiography (OCTA). Methods. This was a cross-sectional study. A total of 25 eyes of 25 healthy volunteers and 30 eyes of 17 patients with RP were evaluated in this study. The integrity of the ellipsoid zone in the macular fovea was evaluated as an intact or defect using a spectral-domain OCT. Commercial spectral domain coherence tomography angiography (OCTA) was used to scan the macular region of approximately 3 × 3 mm2. The vessel density in the SCP and DCP were calculated after appropriate layer segmentation and removal of projection artifacts. The central retinal thickness (CRT) was measured with automated software. The vessel densities in the SCP and DCP were compared between different groups using SPSS. Results. A total of 25 eyes of 25 healthy subjects and 30 eyes of 17 patients with RP were evaluated in the study. There was no significant difference in ages between the two groups (F = 0.065 and P = 0.937 ). There was a significant difference in SCP and DCP between the patients with RP and healthy individuals ( P < 0.001 and P < 0.001 ). The DCP was significantly reduced in the parafovea region between the macular intact and defect groups P < 0.05 , except in the fovea and nasal regions. After linear regression, the DCP/SCP ratio in the whole, fovea, and parafovea regions was closely related to the DCP vessel density P < 0.05 , and CRT in the fovea and parafovea was not related to the whole DCP ( P = 0.186 and P = 0.539 ). Conclusion. The vessel density decreased in patients with RP, especially in the DCP of the parafovea region. A greater loss of capillaries in the DCP was found when the macular region was involved. The DCP/SCP ratio may be an important indicator of RP.

Clinical Observation of Retinal Vessel Density In Type 2 Diabetic Patients With High Mopyopia

Purpose: To quantitatively analyze the difference of superficial and deep retinal vessel density between diabetic patients with high myopia , diabetic patients without high myopia and normal subjects.Methods: This cross-sectional study recruited type 2 diabetic patients with no history of ocular treatment in Shijiazhuang, China.Thirty type 2 diabetic patients with high myopia (30 eyes) were included in group A, 30 type 2 diabetic patients (30 eyes) without myopia were included in group B. Another 30 sex-,age-matched healthy volunteers (30 eyes)were included in group C. The superficial and deep retinal vessel density were measured and compared among the three groups to determine the effects of high myopia on diabetes.Results: No statistically significant differences in central superficial retinal vessel density(CSVD) was found in three groups（P＞0. 05).There were significant differences in the temporal superficial retinal vessel density（TSVD）,superior superficial retinal vessel density(SSVD), nasal superficial retinal vessel density(NSVD),inferior superficial retinal vessel density(ISVD) between the three groups, respectively (P＜0.05).TSVD,SSVD,NSVD,ISVD in group A were all lower than those in group B and group C(P ＜0.05).ISVD in group B was lower than that in group C and no statistically significant differences in TSVD,SSVD,NSVD were found between groups B and C(P＞0.05). There were significant differences in central deep retinal vessel density(CDVD),temporal deep retinal vessel density(TDVD),superior deep retinal vessel density(SDVD), nasal deep retinal vessel density(NDVD),inferior deep retinal vessel density(IDVD) between the three groups, respectively (P＜0.05).CDVD in group A was higher than that in group B , but there was no significant difference between group A and group C.TDVD,SDVD,NDVD,IDVD in group A were all lower than those in group B and C(P ＜0.05),and those in group B were lower than those in group C(P ＜0.05).Conclusion: Myopia and diabetes are important factors affecting vessel density. The parafoveal superficial and deep vessel density of type 2 diabetic patients with high myopia were lower than those of diabetics and normal persons. However,there was no difference in macular fovea superficial and deep retinal vessel density between diabetic patients with high myopia and normal persons.Myopia did not show a protective effect on retinal vessel density reduction in diabetic patients.