Absolute retinal blood flow in healthy eyes and in eyes with retinal vein occlusion.

PURPOSE: To measure non-invasively retinal venous blood flow (RBF) in healthy subjects and patients with retinal venous occlusion (RVO). METHODS: The prototype named AO-LDV (Adaptive Optics Laser Doppler Velocimeter), which combines a new absolute laser Doppler velocimeter with an adaptive optics fundus camera (rtx1, Imagine Eyes®, Orsay, France), was studied for the measurement of absolute RBF as a function of retinal vessel diameters and simultaneous measurement of red blood cell velocity. RBF was measured in healthy subjects (n = 15) and patients with retinal venous occlusion (RVO, n = 6). We also evaluated two softwares for the measurement of retinal vessel diameters: software 1 (automatic vessel detection, profile analysis) and software 2 (based on the use of deep neural networks for semantic segmentation of vessels, using a M2u-Net architecture). RESULTS: Software 2 provided a higher rate of automatic retinal vessel measurement (99.5 % of 12,320 AO images) than software 1 (64.9 %) and wider measurements (75.5 ± 15.7 µm vs 70.9 ± 19.8 µm, p < 0.001). For healthy subjects (n = 15), all the retinal veins in one eye were measured to obtain the total RBF. In healthy subjects, the total RBF was 37.8 ± 6.8 µl/min. There was a significant linear correlation between retinal vessel diameter and maximal velocity (slope = 0.1016; p < 0.001; r2 = 0.8597) and a significant power curve correlation between retinal vessel diameter and blood flow (3.63 × 10-5 × D2.54; p < 0.001; r2 = 0.7287). No significant relationship was found between total RBF and systolic and diastolic blood pressure, ocular perfusion pressure, heart rate, or hematocrit. For RVO patients (n = 6), a significant decrease in RBF was noted in occluded veins (3.51 ± 2.25 µl/min) compared with the contralateral healthy eye (11.07 ± 4.53 µl/min). For occluded vessels, the slope between diameter and velocity was 0.0195 (p < 0.001; r2 = 0.6068) and the relation between diameter and flow was Q = 9.91 × 10-6 × D2.41 (p < 0.01; r2 = 0.2526). CONCLUSION: This AO-LDV prototype offers new opportunity to study RBF in humans and to evaluate treatment in retinal vein diseases.

INTERVORTEX VENOUS ANASTOMOSIS IN Pachychoroid-RELATED DISORDERS.

PURPOSE: To evaluate the choroidal vascular patterns of patients with pachychoroid-related diseases in eyes images with wide-field indocyanine green angiography. METHODS: Retrospective study of wide-field indocyanine green angiographic images of patients with pachychoroid, peripapillary pachychoroid syndrome, central serous chorioretinopathy, and pachychoroid-associated neovascularization that were evaluated for anastomoses between vortex vein systems, which are ordinarily separated by a watershed zone. RESULTS: There were 21 subjects with a mean age of 57.4 years and 15 were male. Among the 42 eyes evaluated, central serous chorioretinopathy was found in 24 eyes (57.1%), peripapillary pachychoroid syndrome in 5 (11.9%), pachychoroid associated neovascularization in 7 (16.7%), and pachychoroid in 6 (14.3%). Every eye showed anastomosis between the superonasal, superotemporal, and inferotemporal vortex vein systems. The inferonasal vortex vein system was less likely to demonstrate anastomosis except for peripapillary pachychoroid syndrome, which showed anastomosis in all eyes. The anastomotic connections were prominent in the central macula in the central serous chorioretinopathy and pachychoroid-associated neovascularization cases, and around the nerve in the peripapillary pachychoroid syndrome cases. Although the large choroidal veins were particularly prominent in the neovascular cases, the number was fewer in the macular region than in other pachychoroid-related diseases in this series. Compared with a control group of nine eyes, the inferotemporal-superotemporal-superonasal anastomotic connections were more common in the case group (P < 0.001) and inferonasal quadrant (P = 0.023 right eye; P = 0.01, left eye). CONCLUSION: Intervortex venous anastomosis is common in pachychoroid, central serous chorioretinopathy, peripapillary pachychoroid syndrome, and pachychoroid-associated neovascularization. This finding has important implications concerning pathogenesis and classification of disease.

NONPERFUSION ASSESSMENT IN RETINAL VEIN OCCLUSION: Comparison Between Ultra-widefield Fluorescein Angiography and Widefield Optical Coherence Tomography Angiography.

PURPOSE: To compare widefield optical coherence tomography angiography (OCTA) to ultra-widefield fluorescein angiography (UWFA) in the assessment of nonperfusion in retinal vein occlusion (RVO). METHODS: A cross-sectional study of 43 eyes of 43 patients with RVO examined using both widefield OCTA (PLEX Elite, Carl Zeiss Meditec, Dublin, CA) with a panoramic montage of five 12 × 12-mm images and UWFA (Optos, 200°). Qualitative analysis was performed according to nonperfusion areas (cutoff: three disk areas) on widefield OCTA. The quantitative analysis assessed the vascular density on the widefield OCTA and ischemic index on UWFA. RESULTS: The ischemic index on UWFA and vascular density in the superficial and deep plexus correlated significantly (P = 0.019, r = 0.357 and P < 0.013, r = 0.375, respectively). The qualitative classification on widefield OCTA and ischemic index on UWFA correlated significantly (P < 0.001, r = 0.618). For the detection of marked nonperfusion (ischemic index ≥ 25%), widefield OCTA had a sensitivity of 100% and a specificity of 64.9%. CONCLUSION: The presence of nonperfusion on UWFA correlated with widefield OCTA. Optical coherence tomography angiography could help to identify high-risk RVO patients who might benefit from a further evaluation using fluorescein angiography.

NONPERFUSION AREA QUANTIFICATION IN BRANCH RETINAL VEIN OCCLUSION: A Widefield Optical Coherence Tomography Angiography Study.

PURPOSE: To precisely quantify retinal nonperfusion areas (NPAs) in branch retinal vein occlusion using widefield optical coherence tomography angiography (OCTA) and examine their association with neovascular complications. METHODS: We enrolled 26 patients with treatment-naïve branch retinal vein occlusion and prospectively examined them for 12 months. After 3 monthly ranibizumab injections to treat macular edema, each patient underwent ultra-widefield (UWF) fluorescein angiography (FA) and OCTA. Ultra-widefield FA was additionally performed at Month 12. For UWF FA, the retinal NPA was measured using the equipment's built-in software. For OCTA, we used panoramic image montaged from 5 single 12 × 12 mm2 images and quantified the retinal NPA using a Gullstrand eye with a grid scale at each patient. Measurements were expressed in terms of actual values and disc area units. RESULTS: The retinal NPAs as measured using single OCTA and panoramic OCTA were significantly associated with that measured using UWF FA (P < 0.001 for both). Retinal neovascularization lesions were observed in 4 (15.4%) of 26 eyes. For patients with accompanying neovascularization, the retinal NPA measured using UWF FA, single OCTA, and panoramic OCTA were 187.9 ± 39.5 mm2 (109.9 ± 21.4 disc area), 34.3 ± 13.7 mm2 (19.9 ± 7.7 disc area), and 106.6 ± 24.5 mm2 (62.4 ± 13.6 disc area), respectively, which were larger than for those without neovascularization (P < 0.001, 0.014, and <0.001, respectively). CONCLUSION: Using widefield OCTA, we could quantify the retinal NPA of eyes with branch retinal vein occlusion. These could serve as valid references to assess the risk of neovascular complications.

ROLE OF DILATED SUBFOVEAL CHOROIDAL VEINS IN EYES WITH MYOPIC MACULAR NEOVASCULARIZATION.

PURPOSE: To investigate the dilated choroidal veins (DCVs) at or around myopic macular neovascularizations (MNVs) and to determine whether there is a hemodynamic relationship between them. METHODS: Fifty-eight eyes of 57 patients with myopic MNVs were examined. Dilated choroidal veins were defined as choroidal veins whose diameter was 2X larger than adjacent veins. Indocyanine green angiography and swept-source optical coherence tomography images were reviewed to detect DCVs that crossed the subfoveal area. The filling sequence of the DCVs and MNVs was determined. RESULTS: Patients' mean age was 71.4 ± 10.6 years. The mean axial length was 29.3 ± 1.8 mm. Dilated choroidal veins below or around the MNV were found in 17 eyes (29.3%). Emissaries of the short posterior ciliary arteries were seen at or around MNVs in 8 of the 17 eyes. In these eyes, the short posterior ciliary artery was filled first or almost simultaneously with the filling of the MNV, followed by a laminar filling of the DCVs. In one eye, afferent arterioles from the short posterior ciliary arteries and efferent venules connected to DCVs were seen. CONCLUSION: Dilated choroidal veins are present below or around MNVs in about 30% of eyes with myopic MNVs. Our findings suggest that an MNV might be a vascular unit consisting of short posterior ciliary arteries, afferent arterioles, efferent venules, and DCVs.

Comparison of Static Retinal Vessel Caliber Measurements by Different Commercially Available Platforms.

SIGNIFICANCE: Commercially available platforms show good agreement in clinical outcomes for retinal vessel caliber measurements, despite differing absolute values. Tighter agreement is observed when right and left eye data are averaged, suggesting an approach suitable for clinical practice. PURPOSE: The purpose of this study was to compare the retinal vessel caliber measurements generated by different commercially available platforms and their associations with systemic blood pressure and age. METHODS: A total of 209 participants were recruited from a UK optometric practice. After a routine eye examination, participants had disc-centered retinal photographs and systemic blood pressure taken. Retinal vessel calibers (central retinal artery equivalent, central retinal vein equivalent, and arteriovenous ratio) were calculated using both MONA REVA and VesselMap. RESULTS: An inverse Pearson correlation was observed between central retinal artery equivalent and mean arterial blood pressure on both platforms (r = -0.275 [P ≤ .001] and r = -0.388 [P ≤ .001] for MONA REVA and VesselMap, respectively); this correlation was also observed with arteriovenous ratio and blood pressure. An inverse correlation was observed between central retinal artery equivalent and age (r = -0.362 [P ≤ .001] and r = -0.404 [P ≤ .001] for MONA REVA and VesselMap, respectively); this was also seen between central retinal vein equivalent and age (r = -0.322 [P ≤ .001] and r = -0.369 [P ≤ .001]). Arteriovenous ratio remained independent from age for both platforms. Bland-Altman plots demonstrated good agreement between the platforms for all three variables. CONCLUSIONS: Although absolute caliber measurements differed between the platforms, the correlations observed were of similar magnitudes, with good agreement between the two platforms. Tighter spaced limits of agreement were observed when right and left eye data were averaged for each subject. In the absence of localized ocular pathology, this approach should be used.

[Venous blood flow in ocular vessels of patients with active retinopathy of prematurity]. / Osobennosti venoznogo krovotoka v sosudakh glaza pri aktivnoi retinopatii nedonoshennykh.

PURPOSE: To study the characteristics of venous circulation in the eyes with retinopathy of prematurity (ROP) observed in examination of blood flow in the central retinal vein and superior orbital vein in patients with different forms, stages and state of the disease. MATERIAL AND METHODS: Color duplex scanning of the central retinal vein and superior orbital vein was performed using color Doppler imaging and pulsed Doppler sonography in 55 premature babies (55 eyes) with active ROP and 8 premature babies (8 eyes) with no signs of ROP. All babies included in the study were born at 25-32 weeks of gestation, their birth weight was 680-1760 g. RESULTS: A characteristic feature of hemodynamic parameters in the central retinal vein at stages 1-3 of active ROP was a decrease in both the maximum and minimum blood flow velocities (Vmax and Vmin), indicating a serious disorder of ocular hemodynamics in this category of patients. An increase in Vmax in the central retinal vein was recorded for patients with aggressive posterior ROP, which occurs in response to venous stasis that is common in this form of the disease. The performed statistical assessment of the prognostic significance of hemodynamic parameters of the central retinal vein in relation to the type of active ROP revealed a high information content of Vmin, which is promising for early detection of unfavorable course of the disease helping to ensure timely treatment. The blood flow in the superior orbital vein showed distinctive absence of any correlations with the course of the disease, disallowing any immediate conclusions on the informativeness and predictive value of its parameters. CONCLUSION: The revealed features of venous blood flow in patients with active ROP help expand the understanding of vascular changes in this pathology, and can also be applied in clinical practice to improve the accuracy of predicting the course of the disease.

Spontaneous Venous Pulsations Detected With Infrared Videography.

BACKGROUND: Assessment of spontaneous venous pulsation (SVP) is commonly undertaken to help determine whether intracranial pressure (ICP) is elevated. Previous studies using direct ophthalmoscopy or slit-lamp assessments have found that SVP is not observed in 67%-81% of subjects with normal ICP, and that interobserver agreement when grading SVP is poor. METHODS: Patients (n = 105) undergoing clinically indicated retinal OCT scans, who were all believed to have normal ICP, had 10-second infrared video recordings performed with the Heidelberg Spectralis OCT system (Heidelberg Engineering GmbH, Heidelberg, Germany). The presence and amplitude of SVP in each video was independently graded by 2 neuro-ophthalmologists. RESULTS: The 2 observers found SVP present in 97% and 98% of right eyes and in one or both eyes in 99% and 100% of subjects. Interobserver agreement was high (Cohen's kappa 0.82 for right eyes). Optic discs with a smaller cup had a significantly lower SVP amplitude (Spearman's rho = 0.22, P = 0.02). CONCLUSIONS: Infrared video is widely available in eye clinics by the use of OCT imaging systems and is substantially more sensitive in detecting SVP than traditional assessments using ophthalmoscopy. SVP is absent in as few as 1% of people with presumed normal ICP.

Associations of retinal microvascular caliber with intermediate phenotypes of large arterial function and structure: A systematic review and meta-analysis.

OBJECTIVE: Intermediate phenotypes of microcirculation (retinal microvascular caliber) are associated with cardiovascular (CV) risk factors and independently predict CV events. However, the effect of microcirculation variation on the vascular system is unclear. We conducted a systematic review and meta-analysis of observational studies to quantify associations of retinal microvascular caliber (arteriolar, venular caliber, arteriole-to-venule ratio) and preclinical CV measures (large arterial function and structure). METHODS: We identified studies in MEDLINE, EMBASE, and PubMed (1946 to March 2018) studying (a) general population samples and (b) patients with cardiometabolic disease. Study-specific correlation estimates were combined into meta-analysis where possible. RESULTS: Of 1294 studies identified, 26 met inclusion criteria (general population 16, patients 10), of which five studies were included in meta-analysis. Most studied middle-aged adults cross-sectionally, with one childhood study. Large arterial function and structure were predominantly assessed by pulse wave velocity and carotid intima-media thickness, respectively. Only arteriolar caliber was consistently associated with arterial function and structure, with stronger associations observed in cardiometabolic patients. Narrower (worse) arteriolar caliber was associated with faster (poorer) pulse wave velocity (correlation coefficient (r) -0.17, 95% CI -0.25 to -0.10) and greater (poorer) intima-media thickness (r -0.05, 95%CI -0.09 to -0.02) across all adult participants. CONCLUSIONS: Retinal arteriolar, but not venular caliber, was modestly associated with large arterial function and weakly associated with large arterial structure, with stronger evidence in patients with cardiometabolic disease. This suggests that preclinical changes in large arteries and the microcirculation have some shared but mainly unique pathways to associate with cardiovascular disease.

Abnormal retinal microvasculature found in active rheumatoid arthritis:a different perspective of microvascular health

Background/aim: We aimed to assess the association between retinal vascular caliber (RVC) scores and disease activity in rheumatoid arthritis (RA) patients. Materials and methods: Forty-seven RA patients, 32 systemic lupus erythematosus (SLE) patients, and 45 healthy people were enrolled. RA and SLE patients were subdivided into groups according to C-reactive protein (CRP) levels. RA patients were also grouped according to Disease Activity Score-28 (DAS-28). Fundus photography was performed for all patients. RVC was summarized as the central retinal artery and vein equivalents (CRAE and CRVE). Results: Mean CRVE for RA patients was 213.3 ± 17.8 µm compared with 209.2 ± 14.1 µm for SLE and 217.5 ± 26.2 µm for the control group (P = 0.17). RVC scores did not differ between the CRP-high and CRP-low groups. As the RA disease activity increased, the widening of CRVE became more prominent and statistically significant. When the DAS-28 > 5.1 (CRVE, 220.4 (211.8­246.5) µm) group and DAS-28 ≤ 3.2 (CRVE, 214.4 (172.4­242.3) µm) group were compared, statistical significance was more pronounced (P = 0.03) than when comparing the DAS-28 > 3.2 and DAS-28 ≤ 3.2 groups (P = 0.05). Conclusions: CRVE, which reflects systemic inflammation and possibly increased cardiovascular risk, was significantly increased in active RA patients. The association between retinal venular widening and disease activity, regardless of CRP, may be a sign that RA-related inflammation may have systemic vascular effects even with normal levels of CRP.

Retinal microcirculation imaging in sickle cell disease patients.

OBJECTIVES: To explore the feasibility of a new quantitative method for microvascular function: non-invasive retinal function imaging (RFI). in sickle cell disease (SCD) patients and healthy controls and have it benchmarked against Laser Speckle Contrast Imaging (LSCI) measurements. METHODS: The variability of Microvascular measurements was assessed in 8 SCD patients and 8 healthy matched controls. Measurements were conducted twice on two different study days. RFI was performed for assessment of arterial and venous retinal blood flow. LSCI measurements included post occlusive reactive hyperemia and IBH challenges. Measured variables included basal flow, flow upon occlusion-reperfusion and flow during an IBH. RESULTS: RFI arterial flow and venous flow and LSCI basal flow and peak flow showed excellent intra subject repeatability between days (CVC of 8.5% 9.5%, 7.6% and 7.7% respectively) and between measurements on one day (CVC of 7.0%, 7.7%, 7.6% and 4.7% respectively). RFI arterial flow (p<0.002), and RFI venous flow (p=0.007) differed significantly between SCD patients and controls in as did LSCI basal flow, maximal flow and delta flow during IBH (p<0.0001). CONCLUSIONS: RFI showed low variability for all readout measures, comparable with most microvascular measures from LSCI. The discriminating power of the RFI between SCD patients and controls demonstrate the feasibility of this device for quantitative assessment of the microcirculation in clinical research.

ARTERIAL OXYGEN SATURATION IN NEOVASCULARIZATIONS IN PROLIFERATIVE DIABETIC RETINOPATHY.

PURPOSE: Retinal neovascularizations in proliferative diabetic retinopathy have been proposed to develop from larger retinal venules. However, angiographic evidence suggests that the new vessels may originate from both arterioles and venules, and the vitreous oxygen tension near retinal neovascularizations is similar to that of retinal arterioles. An assessment of the oxygen saturation in neovascularizations may help characterizing the vascular origin of these vessels in proliferative diabetic retinopathy. METHODS: Dual wavelength oximetry was used to study the oxygen saturation in arterioles, venules, and retinal neovascularizations in 40 eyes from 40 patients with proliferative diabetic retinopathy. RESULTS: The oxygen saturation was significantly lower in retinal venules than in arterioles and neovascularizations (P < 0.0001), and after a correction for the influence of vessel diameter, there was no significant difference between the oxygen saturation in retinal arterioles and neovascularizations (P = 0.71). Age at onset and duration of diabetes mellitus contributed significantly to the variation in oxygen saturation of the venules, whereas none of the clinical background parameters contributed to the variation in oxygen saturation in arterioles and neovascularizations. CONCLUSION: The oxygen saturation in retinal neovascularizations in proliferative diabetic retinopathy is similar to that of the arterioles. Neovascularizations may act as shunts to bypass areas of capillary occlusion.

COMPARISON OF THE RETINAL BLOOD FLOW VELOCITY BETWEEN LASER SPECKLE FLOWGRAPHY AND THE RETINAL FUNCTION IMAGER.

PURPOSE: To compare the retinal blood flow velocity using laser speckle flowgraphy (LSFG) and a retinal function imager (RFI) in healthy Japanese subjects. METHODS: This study included a total of 15 eyes of 15 healthy Japanese subjects (mean age, 41.7 ± 17.0 years). The retinal blood flow velocities were separately measured in arteries and veins around the optic disc using LSFG and an RFI. Linear regression analyses were used to analyze possible correlations of retinal blood flow velocities between the devices. RESULTS: The average blood flow velocities using LSFG as the mean blur rate were 18.6 ± 4.8 in arteries and 18.3 ± 5.5 in veins. The average blood flow velocities using the RFI were 3.4 ± 1.1 mm/second in arteries and 2.9 ± 0.9 mm/second in veins. Although retinal blood flow velocities in arteries and veins using LSFG were nearly the same, there were statistical differences in retinal blood flow velocities between arteries and veins using the RFI (P = 0.701 using LSFG, P = 0.041 using the RFI). Significant correlations were found between LSFG and the RFI in arteries and veins (all, P < 0.001). CONCLUSION: There were strong positive correlations in retinal blood flow velocities between LSFG and the RFI in healthy subjects.

Invagination of Retinal Vein into Conus Pit in a Case with Pathologic Myopia.

Background: Conus pits are reported to occur in eyes with pathologic myopia due to mechanical expansion of peripapillary region. We would like to report a case which had the peculiar pattern of a retinal vein at the site of conus pit. Case: A 61-year old woman with pathologic myopia who had been regularly followed in the High Myopia Clinic at Tokyo Medical and Dental University. The refractive error was -21.4 diopters (D) in the right eye and -22.8 D in the left. The axial length was 32.0 mm in the right eye and 31.7 mm in the left. The optic disc was vertically elongated and deformed. Conus pit was observed temporal to the optic disc in the left eye. The retinal vein was invaginated into the conus pit and lay in an abnormal position. OCT showed that the entire sclera was dehisced at the conus pit. Conclusion: The invagination of the retinal vein occured at the site of conus pits due to pathologic myopia.

[Selective symptomatic therapy of macular edema due to occlusive processes in retinal venous system]. / . Simptomaticheskaia selektivnaia terapiia makuliarnogo oteka pri okkliuzionnykh protsessakh v sisteme retinal'nykh ven.

AIM: to evaluate the effect of dexamethasone intravitreal implant on the functional state of the eye in macular edema associated with central retinal vein occlusion. MATERIAL AND METHODS: The study included two groups of patients: group 1 (control group) - 8 patients (16 eyes) without ocular pathology and group 2 (study group) - 8 patients (8 eyes) with macular edema on the background of newly diagnosed thrombosis of the central retinal vein. All the patients from the study group underwent insertion of an intravitreal dexamethasone implant - Ozurdex. Best corrected visual acuity (BCVA) and retinal light sensitivity of the central visual field were followed up. The maximum follow-up period was 12 months. RESULTS: In group 1 (controls), BCVA averaged 0.93±0.2 and retinal light sensitivity of the central visual field - 19.01±1.18 dB. In group 2, baseline BCVA and retinal light sensitivity were 0.08±0.02 and 4.23±0.2 dB, 1 month after Ozurdex implantation - 0.21±0.04 and 11.77±0.98 dB, at 12 months - 0.23±0.17 and 5.2±0.78 dB, respectively. CONCLUSION: Macular edema associated with central retinal vein thrombosis has a strong deteriorating effect on the functional state of the eye. The dexamethasone intravitreal implant in patients with postthrombotic macular edema contributes to functional improvement, including BCVA and light sensitivity of the central retina, over the first year. At that, different functional parameters show different dynamics after dexamethasone treatment. Light sensitivity values, in contrast to BCVA, change unevenly and significantly during the year. Intravitreal implantation of a dexamethasone implant in patients with postthrombotic macular edema is an effective symptomatic treatment of occlusive processes within the retinal venous system.

Assessment of potential vessel segmentation pitfalls in the analysis of blood flow velocity using the Retinal Function Imager.

PURPOSE: The purpose of our study was to investigate the potential pitfalls associated with different vessel segmentation methods using the built-in software of the Retinal Function Imager (RFI) for the analysis of retinal blood flow velocity (BFV). METHODS: Ten eyes of nine healthy subjects were enrolled in the study. Retinal blood flow measurements were obtained with the RFI device with a 20° field of view imaging. The same grader segmented the retinal vasculature using the RFI software in both sessions, with segments ranging in length from 50 to 100 pixels ("short segments") and 100-200 pixels ("long segments"). The blood flow velocities for the arteriolar and venular system were calculated, and the percentage of excluded vessel segments with high coefficients of variation (>45 %) was recorded and compared by paired t test. Spearman's correlation was used to analyze the relationship between measurements by the two vessel segmentation methods. RESULTS: The number of analyzed vessel segments did not differ significantly between the two groups (28.6 ± 2.6 short and 26.7 ± 4.6 long segments), while the percentage of acceptable segments was significantly higher in the long segment group (65.2 ± 11.4 % vs 85.2 ± 5.87 %, p = 0.001). In the short segment group, more than 15 % of vessel segments were rejected in all subjects, while in the long segment group only three subjects had a rejection rate of greater than 15 % (16.7 %, 18.7 % and 28 %). Both arteriolar and venular velocities were lower in the short segment group, although it reached significance only for arteriolar velocities (3.93 ± 0.55 vs. 4.45 ± 0.76 mm/s, p = 0.036 and 2.95 ± 0.56 vs. 3.17 ± 0.84 mm/s, p = 0.201 for arterioles and venules, respectively). Only venular velocities showed significant correlation (p = 0.003, R (2) = 0.67) between the two groups. CONCLUSIONS: Our results suggest that BFV measurements by the RFI may be affected by segment length, and care should therefore be taken in choosing vessel segment lengths used during the analysis of RFI data. Long segments of 100-200 pixels (400-800 µm) seem to provide more robust measurements, which can be explained by the analysis methodology of the RFI device.

CHARACTERIZATION OF THE MIDDLE CAPILLARY PLEXUS USING OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IN HEALTHY AND DIABETIC EYES.

PURPOSE: To assess the ability of optical coherence tomography angiography to image the retinal middle capillary plexus (MCP), and to characterize the MCP as a unique vascular network separate from the superficial and deep capillary plexus (DCP). METHODS: Healthy and diabetic eyes were imaged using the Avanti XR optical coherence tomography angiography instrument (Optovue Inc, Fremont, CA). Using manual segmentation of the retinal layers, the authors generated en face angiograms to distinguish the three capillary plexuses (superficial capillary plexus, MCP, DCP). RESULTS: In healthy eyes, arterioles gave rise to distinct branches in the MCP, and venules gave rise to prominent vortex like branches in the DCP. The foveal avascular zone was most well-defined at the level of the MCP, and had a larger area in the DCP. In diabetic eyes, the three capillary plexuses showed varying degrees of nonperfusion, including variable shapes and extent of the foveal avascular zone, with loss of border integrity at the MCP. Microaneurysms appeared in all the three capillary plexuses. CONCLUSION: Using customized segmentation analysis in optical coherence tomography angiography, the authors demonstrate that the MCP is qualitatively and functionally distinct from the superficial capillary plexus and DCP, which may help clarify the pathogenesis of different middle retinal ischemic entities and provide new insights into retinal ischemia in diabetic retinopathy.

Monitoring of central retinal artery and vein with color Doppler ultrasound during heart surgery as an alternative to transcranial Doppler ultrasonography: a case report.

Cardiac surgery can have severe neurologic complications. The noninvasive monitoring of intracranial circulation during heart surgery is usually performed with transcranial Doppler ultrasonography. We present the case of a 66-year-old man who underwent elective cardiac surgery for aortic valve replacement and coronary artery bypass graft, in whom monitoring was performed by simultaneously assessing blood flow velocity in the central retinal artery and vein.

Retinal artery to vein ratio is associated with cerebral microbleeds in individuals with type 1 diabetes.

OBJECTIVES: A third of asymptomatic individuals with type 1 diabetes (T1D) show signs of cerebrovascular disease in brain MRI. These signs associate with advanced stages of diabetic retinal disease, but not in mild or moderate retinopathy. We aimed to evaluate a wider spectrum of retinal changes by exploring the relationship between quantitative measures of retinal vessel parameters (RVP) and cerebrovascular changes in T1D. METHODS: We included 146 neurologically asymptomatic individuals with T1D [51% women, median age 40 (33.0-45.1) years] and 24 healthy, sex-matched and age-matched controls. All individuals underwent a clinical and biochemical work-up and brain MRI, which was evaluated for cerebral microbleeds (CMBs), white matter hyperintensities, and lacunar infarcts. RVPs, including central retinal arteriole (CRAE) and central retinal vein (CRVE) equivalents and the ratio of the two variables (arteriovenous ratio, AVR) were assessed quantitatively by a computer-assisted method (IVAN software, version 3.2.6) from fundus images. RESULTS: Among T1D participants, those with CMBs had a lower arteriovenous ratio (AVR) compared with those without CMBs ( P  = 0.023). AVR was inversely associated with the amount of CMBs ( r  = -0.063, P  = 0.035). CMB prevalence was higher in those with AVR below the median (31%) compared with above the median (16%, P  < 0.001), and this difference was significant also after individuals with only no-to-mild retinopathy were included (28 vs. 16%, P  = 0.005). A correlation between blood pressure and CRAE ( r  = -0.19, P  = 0.025) appeared among those with T1D. CONCLUSION: Regardless of the severity of diabetic retinopathy, AVR is associated with the existence of CMBs in T1D.