Changes In Retinal Microcirculation Research Articles

Retinal microcirculation changes in prediabetic patients with short-term increased blood glucose using optical coherence tomography angiography.

Retinal microcirculation alterations are early indicators of diabetic microvascular complications. Optical coherence tomography angiography (OCTA) is a noninvasive method to assess these changes. This study analyzes changes in retinal microcirculation in prediabetic patients during short-term increases in blood glucose using OCTA. To investigate the changes in retinal microcirculation in prediabetic patients experiencing short-term increases in blood glucose levels using OCTA. Fifty volunteers were divided into three groups: Group 1 [impaired fasting glucose (IFG) or impaired glucose tolerance (IGT)], Group 2 (both IFG and IGT), and a control group. Retinal microcirculation parameters, including vessel density (VD), perfusion density (PD), and foveal avascular zone (FAZ) metrics, were measured using OCTA. Correlations between these parameters and blood glucose levels were analyzed in both the fasting and postprandial states. One hour after glucose intake, the central VD (P = 0.023), central PD (P = 0.026), and parafoveal PD (P < 0.001) were significantly greater in the control group than in the fasting group. In Group 1, parafoveal PD (P < 0.001) and FAZ circularity (P = 0.023) also increased one hour after glucose intake. However, no significant changes were observed in the retinal microcirculation parameters of Group 2 before or after glucose intake (P > 0.05). Compared with the control group, Group 1 had a larger FAZ area (P = 0.032) and perimeter (P = 0.018), whereas Group 2 had no significant differences in retinal microcirculation parameters compared with the control group (P > 0.05). Compared with Group 1, Group 2 had greater central VD (P = 0.013) and PD (P = 0.008) and a smaller FAZ area (P = 0.012) and perimeter (P = 0.010). One hour after glucose intake, Group 1 had a larger FAZ area (P = 0.044) and perimeter (P = 0.038) than did the control group, whereas Group 2 showed no significant differences in retinal microcirculation parameters compared with the control group (P > 0.05). Group 2 had greater central VD (P = 0.042) and PD (P = 0.022) and a smaller FAZ area (P = 0.015) and perimeter (P = 0.016) than Group 1. At fasting, central PD was significantly positively correlated with blood glucose levels (P = 0.044), whereas no significant correlations were found between blood glucose levels and OCTA parameters one hour after glucose intake. A short-term increase in blood glucose has a more pronounced effect on retinal microcirculation in prediabetic patients with either IFG or IGT.

Parafoveal capillary density as a potential biomarker in the assessment of diabetic retinopathy progression

AbstractPurposeThe aim of this study was to assess longitudinal changes in retinal vessel density in diabetic patients using optical coherence tomography angiography (OCTA) to identify the most sensitive parameter for detecting retinopathy progression.MethodsPatients with diabetes mellitus were enrolled in this study. Each study subject underwent two imaging sessions, during which three OCTA images of the macular area and three images of the optic nerve head were obtained. The two sessions took place one year apart. The OCTA imaging was performed using an AngioVue device. Superficial vessel density was evaluated in the central 3 mm and parafoveal area, and the nonflow area was measured using the built-in automated AngioAnalytics software of the Optovue system.ResultsThis study included 78 eyes of 39 diabetic patients (age: 55.16 ± 13.73 years) with a mean of 7.70 ± 1.07 mmol L−1 HgA1c level at baseline. At the one-year visit, the eyes of the diabetic subjects had significantly lower superficial vessel density in the parafoveal macula compared to corresponding values at baseline (p &lt; 0.05). There was no statistically significant difference between the baseline and one-year results for the other vascular density parameters and the foveal avascular zone (p &gt; 0.05).ConclusionAt the one-year follow-up, we found that vessel density had decreased in the parafoveal ring in these patients, while there was no significant change in other vascular parameters. This result suggests that superficial parafoveal capillary density is the most sensitive OCTA parameter that can be used as a biomarker for diabetic retinopathy progression. None of the other vascular density parameters nor the foveal avascular zone were able to indicate the subtle changes in retinal microcirculation due to the progression of diabetic microvasculopathy.

Связь парацентральной острой срединной макулопатии и гипертонической болезни

Purpose. To study changes in retinal microcirculation and the prevalence of chronic paracentral acute middle maculopathy (PAMM) lesions in patients with mild hypertension. Participants. Twenty-seven patients (21 males and 6 females 50.3 ± 6.3 years) with mild hypertension without cardiovascular risk and 24 healthy subjects (15 males and 9 females, 46.3 ± 13.0 years) were included. Methods. The foveal avascular zone (FAZ) area, vessel density of superficial and deep capillary plexus were assessed using optical coherence tomography (OCT) angiography. The presence of chronic PAMM lesions was evaluated by the revision of cross-sectional OCT images of 6-mm volume scans. A chronic or resolved PAMM lesion was defined as inner nuclear layer thinning with outer plexiform layer disruption. Results. There was no difference between hypertensive and healthy group in baseline characteristics, vessel density of superficial capillary plexus, vessel density of deep capillary plexus and FAZ area. Chronic PAMM lesions were found in 88.9 % hypertensive patients and in 16.7 % healthy individuals. The odds ratio for the presence of chronic PAMM lesions in mild hypertension was 40.0 (p &lt; 0.001). Conclusion. Chronic PAMM lesions are highly prevalent in hypertensive patients and may represent the earliest changes in retinal microcirculation in mild hypertension, before changes in OCT angiography parameters have become apparent. Keywords: paracentral acute middle maculopathy, hypertension, optical coherence tomography

Optical coherence tomography angiography in the diagnosis of multiple sclerosis

This study analyzes the main changes in retinal microcirculation in patients with multiple sclerosis (MS) and their relationship with the type of disease course. 159 patients (318 eyes) were examined. The groups were formed according to the type of course and duration of MS: group 1 - 37 patients (74 eyes; 23.27%) with relapsing-remitting MS (RRMS) less than 1 year; group 2 - 47 patients (94 eyes; 29.56%) with RRMS from 1 year to 10 years; group 3 - 44 patients (86 eyes; 27.05%) with RRMS >10 years; group 4 - 32 patients (64 eyes; 20.12%) with secondary progressive MS (SPMS). Subgroups A and B were allocated within each group depending on the absence or presence of optic neuritis (ON). Patients underwent standard ophthalmological examination, including optical coherence tomography angiography (OCTA). A decrease in the vessel density (wiVD) and perfusion density (wiPD) in the macular and peripapillary regions was revealed, progressing with the duration of the disease and with its transition to the progressive type. The minimum values were observed in patients with SPMS (group 4), with the most pronounced in the subgroup with ON (wiVD = 16.06±3.65 mm/mm2, wiPD = 39.38±9.46%, ppwiPD = 44.06±3.09%, ppwiF = 0.41±0.05). OCTA provides the ability to detect subclinical vascular changes and can be considered a comprehensive, reliable method for early diagnosis and monitoring of MS progression.

Retinal venular vessel diameters are smaller during ten days of bed rest

Older individuals experience cardiovascular dysfunction during extended bedridden hospital or care home stays. Bed rest is also used as a model to simulate accelerated vascular deconditioning occurring during spaceflight. This study investigates changes in retinal microcirculation during a ten-day bed rest protocol. Ten healthy young males (22.9 ± 4.7 years; body mass index: 23.6 ± 2.5 kg·m–2) participated in a strictly controlled repeated-measures bed rest study lasting ten days. High-resolution images were obtained using a hand-held fundus camera at baseline, daily during the 10 days of bed rest, and 1 day after re-ambulation. Retinal vessel analysis was performed using a semi-automated software system to obtain metrics for retinal arteriolar and venular diameters, central retinal artery equivalent and central retinal vein equivalent, respectively. Data analysis employed a mixed linear model. At the end of the bed rest period, a significant decrease in retinal venular diameter was observed, indicated by a significantly lower central retinal vein equivalent (from 226.1 µm, CI 8.90, to 211.4 µm, CI 8.28, p = .026), while no significant changes in central retinal artery equivalent were noted. Prolonged bed rest confinement resulted in a significant (up to 6.5%) reduction in retinal venular diameter. These findings suggest that the changes in retinal venular diameter during bedrest may be attributed to plasma volume losses and reflect overall (cardio)-vascular deconditioning.

Sex Variations in Retinal Microcirculation Response to Lower Body Negative Pressure.

Lower body negative pressure (LBNP) is routinely used to induce central hypovolemia. LBNP leads to a shift in blood to the lower extremities. While the effects of LBNP on physiological responses and large arteries have been widely reported, there is almost no literature regarding how these cephalad fluid shifts affect the microvasculature. The present study evaluated the changes in retinal microcirculation parameters induced by LBNP in both males and females. Forty-four participants were recruited for the present study. The retinal measurements were performed at six time points during the LBNP protocol. To prevent the development of cardiovascular collapse (syncope) in the healthy participants, graded LBNP until a maximum of -40 mmHg was applied. A non-mydriatic, hand-held Optomed Aurora retinal camera was used to capture the retinal images. MONA Reva software (version 2.1.1) was used to analyze the central retinal arterial and venous diameter changes during the LBNP application. Repeated measures ANOVAs, including sex as the between-subjects factor and the grade of the LBNP as the within-subjects factor, were performed. No significant changes in retinal microcirculation were observed between the evaluated time points or across the sexes. Graded LBNP application did not lead to changes in the retinal microvasculature across the sexes. The present study is the first in the given area that attempted to capture the changes in retinal microcirculation caused by central hypovolemia during LBNP. However, further research is needed with higher LBNP levels, including those that can induce pre-fainting (presyncope), to fully understand how retinal microcirculation adapts during complete cardiovascular collapse (e.g., during hypovolemic shock) and/or during severe hemorrhage.

Correlation between optical coherence tomography angiography-based data and postoperative visual acuity in patients that underwent surgery for macula-on RRD and macula-off RRD

Background: Despite advances in surgical techniques for rhegmatogenous retinal detachment (RRD) repair, patients are still at high risk for low functional outcomes. Given the above, it is important to find reasons for disappointment at the outcomes of vitreoretinal surgery for RRD. Impaired retinal microcirculation is a possible cause of insufficiently good functional outcomes in surgery for RRD. Purpose: To compare postoperative optical coherence tomography angiography (OCTA)-based changes in retinal microcirculation in the eyes of patients that underwent surgery for macula-on RRD versus the eyes of patients that underwent surgery for macula-off RRD and (2) to establish a relationship between OCTA data and best-corrected visual acuity (BCVA). Material and Methods: This prospective study included 116 patients. Of these, 65 underwent surgery for macular-on RRD (group 1) and 51, surgery for macular-off RRD (group 2). OCTA-based retinal vasculature parameters (foveal avascular zone (FAZ) area, parafoveal superficial capillary plexus (SCP) density and deep capillary plexus (DCP) density, vessel diameter, and vessel tortuosity index (VTI)) and their correlation with BCVA were assessed. Follow-up duration was 12 months. Results: In group 1, there was a negative correlation between the FAZ area and the macular thickness (r = - 0.299, p = 0.025) at month 12. The final BCVA was associated with the parafoveal DCP density (r = - 0.340, p = 0.010) and FAZ area (r= 0.390, p = 0.003). At 12 months, in group 2, the BCVA negatively correlated with the FAZ area (r = - 0.408, p = 0.012) and parafoveal SCP density (r = - 0.451, p = 0.005). In addition, there was a negative correlation between the parafoveal DCP density and the postoperative BCVA (r = - 0.418). There was no correlation between the FAZ area and the macular thickness (r = - 0.282, p = 0.080). Conclusion: The poorer vessel tortuosity index and parafoveal vessel density and diameter, the lower was postoperative visual acuity.

Pulsatile Ocular Blood Flow Registered with Optical Coherence Tomography Angiography in Patients with High Intraocular Pressure.

To present a series of cases demonstrating pulsatile ocular blood flow registered with optical coherence tomography angiography (OCTA) and to describe the clinical characteristics of this phenomenon. Seven primary open-angle glaucoma patients (eight eyes) were included, with a median age of 67.0 years (range, 39-73 years), who demonstrated alternating hypointense bands of OCTA flow signal on the macular scan at increased intraocular pressure (IOP). All patients received comprehensive ophthalmic examination, OCTA examination with RTVue-XR, and infrared video scanning laser ophthalmoscopy. Changes in retinal microcirculation were assessed on the raw OCTA scans as well as the resultant vessel density maps before and after IOP reduction. Median IOP in study eyes was 39.0 mmHg (range, 36-58 mmHg). Hypointense bands of OCTA flow signal were associated with arterial pulsation on video scanning laser ophthalmoscopy in all eyes and agreed with the heart rate and resulted in a spotted grid pattern of hypoperfusion on vessel density maps in seven eyes. Median vessel density in superficial capillary plexus and deep capillary plexus was 32.4% and 47.2%, respectively, at high IOP, and increased statistically significantly to 36.5% (P = 0.016) and 50.9% (P = 0.016), respectively, after IOP reduction. Alternating hypointense flow signal bands on OCTA scans are possibly caused by the pulsatile character of retinal blood flow during the cardiac cycle in eyes with high IOP and may reflect the imbalance between IOP and perfusion pressure. This phenomenon is responsible for the reversible decrease of vessel density at high IOP.

The effect of systemic factors on retinal blood flow in patients with carotid stenosis: an optical coherence tomography angiography study

Carotid artery stenosis (CAS) is among the leading causes of mortality and permanent disabilities in the Western world. CAS is a consequence of systemic atherosclerotic disease affecting the majority of the aging population. Optical coherence tomography angiography (OCTA) is a novel imaging technique for visualizing retinal blood flow. It is a noninvasive, fast method for qualitative and quantitative assessment of the microcirculation. Cerebral and retinal circulation share similar anatomy, physiology, and embryology; thus, retinal microvasculature provides a unique opportunity to study the pathogenesis of cerebral small vessel disease in vivo. In this study, we aimed to analyze the effect of systemic risk factors on retinal blood flow in the eyes of patients with significant carotid artery stenosis using OCT angiography. A total of 112 eyes of 56 patients with significant carotid stenosis were included in the study. We found that several systemic factors, such as decreased estimated glomerular filtration rate (eGFR), hypertension, and carotid occlusion have a significant negative effect on retinal blood flow, while statin use and carotid surgery substantially improve ocular microcirculation. Neither diabetes, clopidogrel or acetylsalicylic acid use, BMI, serum lipid level, nor thrombocyte count showed a significant effect on ocular blood flow. Our results demonstrate that a systematic connection does exist between certain systemic risk factors and retinal blood flow in this patient population. OCTA could help in the assessment of cerebral circulation of patients with CAS due to its ability to detect subtle changes in retinal microcirculation that is considered to represent changes in intracranial blood flow.

Early changes in retinal microcirculation after uncomplicated cataract surgery using an active-fluidics system.

To evaluate the early changes in retinal microcirculation after uncomplicated cataract surgery using an active-fluidics system. Patients underwent uncomplicated cataract surgery for both eyes were enrolled. The two eyes of the patients were randomly assigned to two groups, the active-fluidics group and the gravity-fluidics group. One eye using an active-fluidics system, and the other using a gravity-fluidics system. Optical coherence tomography angiography (OCTA) was performed at 1day, 7days, 30days, and 90days after surgery. Fifty eyes (25 patients) were included in the final analysis. A significantly lower cumulative dissipated energy (CDE), estimated fluid usage (EFU), and total aspiration time (TAT) were observed in the active-fluidics group (all P<0.05). The superficial vessel density at parafoveal region increased at 7days and 30days after cataract surgery in the eyes of both the active-fluidics and gravity-fluidics groups, with the fluctuation in eyes of the gravity-fluidics group more significant. The vessel density of deep capillary plexus remained stable during the follow-up period. Significant changes of retinal thickness in macular region (fovea, parafovea) were observed in eyes of the gravity-fluidics group through the comparison of corresponding values at different time points (p = 0.008, 0.005). No significant change in retinal thickness was observed in eyes of the active-fluidics. Retinal microcirculation and thickness were disturbed after cataract surgery using the gravity-fluidics infusion system. The active-fluidics system not only improved the surgical efficacy but also protected the retinal vasculature during cataract surgery. The study has been registered at www.clinicaltrials.gov with its clinical trial accession number of NCT0130500.

Reference values of retinal microcirculation parameters derived from a population random sample

Retinal microcirculation reflects retinal perfusion abnormalities and retinal arterial structural changes at relatively early stages of various cardiovascular diseases. Our objective has been to establish reference values for major functional and structural parameters of retinal microcirculation in a randomly selected urban population sample.A total of 398 randomly selected individuals from an urban population aged 25 to 65 years, resident in Pilsen, Czech Republic, were screened for major cardiovascular risk factors. Retinal microcirculation was assessed using scanning laser Doppler flowmetry (SLDF), with data evaluable in 343 patients. Of this number, complete data were available for 256 individuals free from manifest cardiovascular disease, diabetes and drug treatment for hypertension and/or dyslipidemia, constituting the reference value population.Juxtapapillary retinal capillary blood flow has increased significantly with age whereas vessel and luminal diameters have decreased. No sex differences in retinal microcirculation parameters have been found. Therefore, reference values for retinal microcirculation parameters have been established by age groups. Unattended automated office systolic BP, after adjusting for age, correlated significantly with wall-to-lumen ratio (WLR) and wall thickness (WT). Moreover, after adjusting for age and mean BP, a positive relationship has been found between carotid femoral pulse wave velocity and WT, WLR and wall cross-sectional area, indicating the interaction between micro- and macro-vasculature.In conclusion, our study is the first to provide reference values of retinal microcirculation parameters in a random Caucasian population sample. Our results have shown that, at the population level, the first structural changes in retinal microcirculation are those in lumen diameters. Of note, a close relationship between BP and vascular remodeling of retinal arterioles and between aortic stiffness and WLR of retinal arterioles suggests an interaction between micro- and macro-vasculature.

Effects of Diabetes on Microcirculation and Leukostasis in Retinal and Non-Ocular Tissues: Implications for Diabetic Retinopathy.

Changes in retinal microcirculation are associated with the development of diabetic retinopathy (DR). However, it is unclear whether such changes also develop in capillary beds of other non-retinal tissues. Here, we investigated microcirculatory changes involving velocity of rolling neutrophils, adherence of neutrophils, and leukostasis during development of retinal vascular lesions in diabetes in other non-retinal tissues. Intravital microscopy was performed on post-capillary venules of cremaster muscle and ear lobe of mice with severe or moderate diabetes and compared to those of non-diabetic mice. Additionally, number and velocity of rolling leukocytes, number of adherent leukocytes, and areas of leukostasis were quantified, and retinal capillary networks were examined for acellular capillaries (AC) and pericyte loss (PL), two prominent vascular lesions characteristic of DR. The number of adherent neutrophils and areas of leukostasis in the cremaster and ear lobe post-capillary venules of diabetic mice was increased compared to those of non-diabetic mice. Similarly, a significant increase in the number of rolling neutrophils and decrease in their rolling velocities compared to those of non-diabetic control mice were observed and severity of diabetes exacerbated these changes. Understanding diabetes-induced microcirculatory changes in cremaster and ear lobe may provide insight into retinal vascular lesion development in DR.

The relationship between the indicators of the retina condition and other target organ changes in uncomplicated essential hypertension

Background. Changes in retinal microcirculation are considered a subtle indicator of the other target organ damage in hypertension and might have prognostic value. Objective. To establish the relationship between diameters of retinal arterioles and venules, foveal avascular zone (FAZ) area, subfoveal choroid thickness with parameters of left heart and kidneys in middle-aged patients with essential hypertension (EH) stage I-II. Design and methods . A total of 115 people (86 males, 29 females) aged 45-59 years were examined and divided into 2 groups. The main group consisted of 70 patients with EH stage I or II. The control group comprised 45 normotensive practically healthy individuals. Patients with diabetes mellitus, impaired liver function, clinically significant ophthalmic pathology were not included. The following data were analyzed: anamnesis including smoking status; routine blood hemodynamic and biochemical parameters, serum procollagen III N-terminal propeptide (PIIINP); albumin-creatinine ratio in a single morning portion of urine, diurnal albuminuria; parameters of 24-h ambulatory blood pressure monitoring; quantitative electrocardiography (ECG) markers of left ventricular hypertrophy; transthoracic echocardiography; fundus state. Based on the scanning laser ophthalmoscopy, the central retinal arterial (CRAE) and venous (CRVE) equivalents, arteriovenous ratio (AVR) were calculated. Using the method of optical coherence tomography angiography, we determined the FAZ area and subfoveal choroid thickness. Statistical data were processed using the StatSoft Statistica 10. Results. Compared with normotensive individuals, patients with hypertension were characterized by lower values of CRAE (p = 0,009), larger FAZ area (p = 0,019), and comparable values of CRVE, AVR, subfoveal choroid thickness (p > 0,05 for each indicator). Correlation analysis showed that in hypertensive AVR correlated with low-density lipoprotein cholesterol level (r = -0,3; p < 0,05); FAZ area with female gender (r = 0,42; p < 0,05); FAZ area with PIIINP level (r = 0,3; p < 0,05); FAZ area with diurnal albuminuria (r = 0,37; p < 0,05); CRVE with R wave amplitude in aVL lead of ECG (r = 0,31; p < 0,05); CRAE with left atrial volume index (r = -0,3; p < 0,05); subfoveal choroid thickness with age (r= -0,3; p = 0,01). Conclusions. Middle-aged patients with uncomplicated EH are characterized by the lower CRVE values and larger FAZ area compared to normotensive individuals. In EH stage I-II, retinal microcirculation parameters are associated with indicators reflecting the other target organ damage, in particular, the left atrial volume index, R wave amplitude in aVL lead of the standard ECG, diurnal albuminuria, and serum PIIINP concentration.

Evaluation of the effect of fingolimod (FTY720) on macular perfusion by swept-source optical coherence tomography angiography in patients with multiple sclerosis

Aim To determine changes in retinal microcirculation, caused by fingolimod (FTY720) use, via swept-source optical coherence tomography angiography (SS-OCTA) in relapsing-remitting multiple sclerosis (RR-MS) patients. Materials and methods 80 patients with RR-MS, who were using fingolimod, and 50 healthy control subjects were included in the study. Group 1 consisted of 40 eyes from 40 RR-MS patients, who had been using fingolimod for less than six months, and Group 2 consisted of 40 eyes from 40 RR-MS patients, who had been using fingolimod for longer than six months. All participants underwent SS-OCTA via DRI OCT Triton (Topcon, Tokyo, Japan), analysing their central macular thickness (CMT) (µm), subfoveal choroidal thickness (SFCT) (µm), superficial (VDs) (%) and deep vascular plexuses (VDd) (%), choriocapillaris (VDcc) (%), and superficial and deep foveal avascular zones (FAZs, FAZd, respectively) (%) in mean values. Results The mean follow-up times for patients in Groups 1 and 2 were 2.9 ± 1.5 months and 22.5 ± 11.3 months, respectively. The FAZs value in Group 2 was found to be significantly higher than that in both Group 1 and the control group (p = 0.034, p = 0.042, respectively). The VDs central value in Group 2 did not differ significantly from that in Group 1 or the control group (p > 0.05), while the VDs central value was higher in Group 1 than in the control group (p = 0.008). In Group 1, the VDd central value was significantly higher than in Group 2 and the control group (p = 0.047; p = 0.020, respectively). The CMT measurement for Group 2 was significantly lower than in Group 1 and the control group (p = 0.008, p = 0.003, respectively). Conclusion Fingolimod use seems to remarkably increase VDs and VDd measurements in the early period of administration and decrease CMT over a longer period of administration in patients with RR-MS.

Rodent retinal microcirculation and visual electrophysiology following simulated microgravity

How the absence of gravity affects the physiology of human beings is generating global research interest as space exploration, including missions aboard the International Space Station, continues to push boundaries. Here, we examined changes in retinal microcirculation and visual electrophysiology in mice suspended by their tails to simulate the cephalad movement of blood that occurs under microgravity conditions. Tail suspension was performed with a head-down tilt with a recommended angle of 30°. Mice in the control groups were similarly attached to a tether but could maintain a normal position. Morphologically, the 15-day tail-suspended mice showed retinal microvascular dilation, tortuosity, and a relatively long fluorescence retention; however, the average diameter of the major retinal vessels was not notably changed. In addition, optical coherence tomography showed their optic nerve head had an increased diameter. However, the mice could adapt to the change, with microcirculation and the optic nerve head recovering following 30-day tail suspension. Expression of rhodopsin and cone-opsins was not notably changed, and no retinal apoptotic-positive cells were detected between 15- and 30-day tail suspensions. Moreover, the three experimental groups of suspended mice showed normal retinal layers and thickness. Functionally, following 15-day tail suspension, scotopic electroretinograms showed a decline in the oscillatory potentials (OPs), but not in the b wave; simultaneously, the peak time of flash visual evoked potential component N1 was delayed compared to its baseline and the time-matched control. Following 30-day tail suspension, the OPs (O2) amplitude recovered to approximately 97% of its baseline or 86% of the time-matched control level. By simulating cephalad shifting of blood, short-term tail suspension can affect rodent retinal microcirculation, the optic nerve head, and disturb visual electrophysiology. However, the change is reversible with no permanent injury observed in the retina. The mice could adapt to the short-term change of retinal microcirculation, indicating new conditions that could be combined with, or could enhance, simulated microgravity for further studying the impact of short- or long-term outer space conditions on the retina.

Association of Chronic Paracentral Acute Middle Maculopathy Lesions with Hypertension

To study changes in retinal microcirculation and the prevalence of chronic paracentral acute middle maculopathy (PAMM) lesions in patients with mild hypertension. Prospective cohort study. Twenty-seven patients (21 men and 6 women; mean age, 50.3±6.3 years) with mild hypertension and with low cardiovascular risk and 24 healthy participants (15 men and 9 women; mean age, 46.3±13.0 years) were included. The foveal avascular zone (FAZ) area and the vessel density of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were assessed using OCT angiography (OCTA). The presence of chronic PAMM lesions was evaluated for both eyes by the revision of cross-sectional OCT images of 6-mm volume scans. A chronic or resolved PAMM lesion was defined as inner nuclear layer thinning with outer plexiform layer (OPL) disruption. Vessel density of the SCP and DCP and prevalence of chronic PAMM lesions. No difference was found between the hypertensive group and healthy group in demographic and clinical characteristics, vessel density of the SCP (48.9±2.4% and 47.8±2.0%, respectively; P= 0.92), vessel density of the DCP (54.1±3.3% and 54.0±1.8%, respectively; P= 0.93), or FAZ area (0.26±0.13 mm2 and 0.23±0.09 mm2, respectively; P= 0.37). Chronic PAMM lesions were found in 24 of 27 (88.9%) hypertensive patients and in 4 of 24 (16.7%) healthy individuals. The odds ratio for the presence of chronic PAMM lesions in patients with mild hypertension was 40.0 (P < 0.001). Chronic PAMM lesions are highly prevalent in hypertensive patients and may represent the earliest changes in retinal microcirculation in patients with mild hypertension, before changes in OCTA parameters have become apparent.

Morphometry of the normal retinal periarteral capillary-free zone and changes during severe nonproliferative diabetic retinopathy.

To explore the normal morphological features of the retinal periarteral capillary free zone (paCFZ) and the changes associated with severe non-proliferative diabetic retinopathy (NPDR) by optical coherence tomography angiography (OCTA). A total of 148 normal subjects and 115 patients with severe NPDR were enrolled. Spectral-domain OCTA was used to acquire the image with a Cirrus prototype. Diameter and area of each paCFZ quadrant and adjacent large artery diameter was estimated. In healthy subjects, the maximum width of paCFZ in the temporal quadrant (169.38 ± 19.26μm) was smaller than the other three quadrants (all P <0.001). The ratio of maximum paCFZ width to artery caliber was much larger in the nasal quadrants than the rest quadrants (Ps <0.05). In patients with severe NPDR, both maximum width and area of paCFZ were significant larger, and the retinal artery inner diameters significant smaller in each quadrant compared to normal subjects (Ps <0.05). The ratio of paCFZ maximum width to artery caliber maximum width was significant greater, and the ratio of paCFZ area to artery caliber was significantly higher in all quadrants compared to normal eyes (Ps <0.05). OCTA provides noninvasive and quantitative measurement of paCFZ dimensions. The maximum width and area of paCFZ quadrants and the ratios of these parameters to adjacent inner artery width and area are elevated in severe NPDR, suggesting that changes in paCFZ dimension can be used as clinical indices for diseases associated with changes in retinal microcirculation and oxygen pressure.PRÉCIS:Optical coherence tomography angiography revealed differences in retinal periarteral capillary free zone (paCFZ) morphometry between health retina and severe non-proliferative diabetic retinopathy. Morphometric indices of paCFZ may be useful for monitoring disease occurrence and progression.

REFERENCE VALUES OF RETINAL MICROCIRCULATION PARAMETERS IN A WHITE POPULATION RANDOM SAMPLE. CZECH POST-MONICA STUDY

Objective: Retinal microcirculation reflects retinal perfusion abnormalities and retinal arterial structural changes at relatively early stages of various cardiovascular diseases. Our objective was to establish reference values for major functional and structural parameters of retinal microcirculation in a randomly selected urban population sample.Design and method: A total of 398 randomly selected individuals from an urban population aged 25 to 65 years, resident in Pilsen, Czech Republic, were screened for major cardiovascular risk factors. Retinal microcirculation was assessed using scanning laser Doppler flowmetry (SLDF), with data evaluable in 345 patients. Of this number, complete data were available for 257 individuals free from manifest cardiovascular disease, diabetes and drug treatment for hypertension and/or dyslipidemia who made up the reference value population. Results: Retinal capillary blood flow (RCF) increased significantly with age whereas vessel and luminal diameters decreased. No sex differences in retinal microcirculation parameters were found. Reference values by age were established (see Table). A comparison between the reference value population and the diseased population (n = 88) derived from the same population sample found significant differences in age, BMI, BP, HbA1c, pulse wave velocity and prevalence of dyslipidemia, with the latter population consistently showing less favorable values. When comparing retinal parameters, after adj. for age, the only differences were found in vessel (reference value population: 103.5 ± 0.8 vs. diseased population: 107.0 ± 1.5 μm; p = 0.05) and luminal diameters (reference value population: 77.1 ± 0.5 vs. diseased population: 80.1 ± 0.9 μm; p = 0.007), with no differences in wall thickness or wall-to-lumen ratio, thus confirming that, at the population level, the first structural changes in retinal microcirculation are changes in lumen diameters. Conclusions: This is the first study providing reference values of retinal microcirculation parameters in a random white population sample. Our results show that, at the population level, the first structural changes in retinal microcirculation are those in lumen diameters.

Changes in Retinal Microcirculation Precede the Clinical Onset of Diabetic Retinopathy in Children With Type 1 Diabetes Mellitus

To investigate whether abnormal glucose metabolism in diabetes mellitus (DM) affects the retinal microcirculation of children with well-controlled type 1 DM and to compare these results with those obtained from healthy children. Cross-sectional prospective study. This study enrolled 60 patients with DM without clinically detectable diabetic retinopathy (DR) and 57 age-matched control subjects. Optical coherence tomography angiography (OCT-A) was performed using AngioVue (Avanti, Optivue). Foveal avascular zone (FAZ) area, nonflow area, superficial and deep vessel densities, FAZ perimeter, acircularity index of FAZ (AI; the ratio of the perimeter of FAZ and the perimeter of a circle with equal area), and foveal density (FD-300; vessel density in 300μm around FAZ) were analyzed. Correlations between the investigated OCT-A parameters with DM duration and glycated hemoglobin (HbA1c) levels were evaluated among patients with type 1 DM. Differences in the mean values for FAZ perimeter, AI, and FD-300 were statistically significant between DM group and control group (P < .001, P=.001, and P= .009, respectively). There were also statistically significant differences between the groups for vessel densities of deep superior hemi-parafovea, deep temporal parafovea, and deep superior parafoveal zones (P= .008, P= .015, and P= .005, respectively). There were no significant correlations between DM duration and HbA1c levels with the investigated OCT-A parameters. Diabetic eyes without clinically detectable DR exhibited alterations in FD-300, AI, perimeter, and vessel density of parafoveal capillaries in deep capillary plexus preceding the enlargement of FAZ; therefore, these new parameters might be sensitive imaging biomarkers to define early DR.

Feasibility of optical coherence tomography angiography to assess changes in retinal microcirculation in ovine haemorrhagic shock

BackgroundThis study aimed to investigate the feasibility of optical coherence tomography angiography (OCT-A) for quantitative analysis of flow density to assess changes in retinal perfusion in an experimental model of haemorrhagic shock.MethodsHaemorrhagic shock was induced in five healthy, anaesthetized sheep by stepwise blood withdrawal of 3 × 10 ml∙kg− 1 body weight. OCT-A imaging of retinal perfusion was performed using an OCT device. Incident dark-field illumination microscopy videos were obtained for the evaluation of conjunctival microcirculation. Haemodynamic variables and flow density data in the OCT angiogram were analysed before and during progressive haemorrhage resulting in haemorrhagic shock as well as after fluid resuscitation with 10 ml∙kg− 1 body weight of balanced hydroxyethyl starch solution (6% HES 130/0.4). Videos of the conjunctival microcirculation were recorded at baseline, in haemorrhagic shock, and after resuscitation. Data are presented as median with interquartile range. Comparisons between time points were made using Friedman’s test and the degree of correlation between two variables was expressed as Spearman’s rank correlation coefficient.ResultsMean arterial pressure and cardiac index (CI) decreased and lactate concentration increased after induction of shock, and haemodynamics recovered after resuscitation. The flow density in the superficial retinal OCT angiogram decreased significantly after shock induction (baseline 44.7% (40.3; 50.5) vs haemorrhagic shock 34.5% (32.8; 40.4); P = 0.027) and recovered after fluid resuscitation (46.9% (41.7; 50.7) vs haemorrhagic shock; P = 0.027). The proportion of perfused vessels of the conjunctival microcirculation showed similar changes. The flow density measured using OCT-A correlated with the conjunctival microcirculation (perfused vessel density: Spearman’s rank correlation coefficient ρ = 0.750, P = 0.001) and haemodynamic parameters (CI: ρ = 0.693, P < 0.001).ConclusionsRetinal flow density, measured using OCT-A, significantly decreased in shock and recovered after fluid therapy in an experimental model of haemorrhagic shock. OCT-A is feasible to assess changes in retinal perfusion in haemorrhagic shock and fluid resuscitation.