Measurement of retinal wall-to-lumen ratio by adaptive optics retinal camera: a clinical research.

PURPOSE: To measure the wall-to-lumen ratio (WLR) and the cross-sectional area of the vascular wall (WCSA) of retinal arterioles by an Adaptive Optics (AO) retinal camera. METHODS: Forty-seven human subjects were examined and their medical history was explored. WLR and WCSA were measured on the basis of retinal arteriolar wall thickness (VW), lumen diameter (LD) and vessel diameter (VD) assessed by rtx1 Adaptive Optics retinal camera. WLR was calculated by the formula [Formula: see text]. Arterio-venous ratio (AVR) and microvascular abnormalities were attained by quantitative and qualitative assessment of fundus photographs. Influence of age, arterial hypertension, body mass index (BMI) and retinal microvascular abnormalities on the WLR was examined. An age-adjusted WLR was created to test influences on WLR independently of age. Considering WLR and WCSA, a distinction between eutrophic and hypertrophic retinal remodeling processes was possible. RESULTS: The intra-observer variability (IOV) was 6 % ± 0.9 for arteriolar wall thickness and 2 % ± 0.2 for arteriolar wall thickness plus vessel lumen. WLR depended significantly on the wall thickness (r = 0.715; p < 0.01) of retinal arterioles, but was independent of the total vessel diameter (r = 0.052; p = 0.728). WLR correlated significantly with age (r = 0.769; p < 0.01). Arterial hypertension and a higher BMI were significantly associated with an increased age-adjusted WLR. WLR correlated significantly with the stage of microvascular abnormalities. 55 % of the hypertensive subjects and 11 % of the normotensive subjects showed eutrophic remodeling, while hypertrophic remodeling was not detectable. WLR correlated inversely with AVR. AVR was independent of the arteriolar wall thickness, age and arterial hypertension. CONCLUSIONS: The technique of AO retinal imaging allows a direct measurement of the retinal vessel wall and lumen diameter with good intra-observer variability. Age, arterial hypertension and an elevated BMI level are significantly associated with an increased WLR. The wall-to-lumen ratio measured by AO can be used to detect structural retinal microvascular alterations in an early stage of remodeling processes.

Adipokines and endothelial dysfunction in obesity WHO°III.

Obesity is closely associated with the metabolic syndrome (MetS) and subsequent low-grade inflammation links to endothelial dysfunction (ED) and cardiovascular disease. The impact of adipokines on retinal ED is not fully understood, in particular not in severe obesity. The aim of the study was to identify the association of the MetS and prespecified adipokines on retinal ED in obesity WHO°III. 92 obese patients (obesity WHO°III) were assessed for the MetS (IDF), neck circumference, adipokines and inflammatory markers (hsCRP, TNFα, Il-6, MCP-1, sICAM, sVCAM, IGF-BP3, RBP 4 and adiponectin). Retinal ED as determined by the arterio-venous-ratio (AVR) and retinal vessel diameters (CRAE, CRVE) was measured using retinal photographs. Obese subjects with MetS (MetS+ group) differed from the MetS- by neck circumference, fasting plasma glucose, insulin, HOMA-IR, triglycerides and HDL-C. Importantly, IL-6, sICAM and adiponectin were significantly different between groups, while measures of retinal ED showed no differences. Univariate linear regression revealed a significant association between neck circumference and ED for patients with MetS, and a significant association between adiponectin and CRAE for patients without MetS. This study shows that ED in obesity WHO°III is independent of MetS or inflammation and that neck circumference has an impact on ED in obesity WHO°III.

Retinal vessel diameters and microvascular abnormalities in patients with carotid stenosis before and 6 months after carotid endarterectomy: A prospective study.

PURPOSE: To assess retinal findings in patients with severe carotid stenosis (CS) before and after carotid endarterectomy (CEA) compared to those in controls. METHODS: This study is based on 70 patients (male 81%, mean age 69) scheduled for CEA in Helsinki University Hospital and 41 healthy nonmedicated controls (male 76%, mean age 68). Our examinations included fundus photographs. Semi-automated software (Vesselmap, Imedos) served for evaluation of central retinal arterial equivalent (CRAE) and venular equivalent (CRVE), and arterio-venous ratio (AVR) in both eyes. We assessed fundus photographs to subjectively grade microvascular abnormalities in the ipsilateral eyes including focal arteriolar narrowing and irregularities, arteriolar wall reflex, arterio-venous crossing signs and arteriolar and venular tortuosity in the macula. RESULTS: CRAE was similar in the ipsi-and contralateral eyes of our patients, and similar to that of the controls both pre- and postoperatively. Preoperatively, we observed higher CRVE in the patients' ipsilateral than in their contralateral eyes (222 vs. 217 µm, p = 0.009), and likewise higher than in controls' eyes (222 vs. 214 µm, p = 0.024). CRVE decreased postoperatively in the patients' ipsilateral eyes (222 vs. 217 µm, p = 0.037). Among the microvascular abnormalities, arteriolar and venular tortuosity in the macula showed higher grades in the patients than in the controls preoperatively (p = 0.035 and p = 0.043), but not postoperatively (p = 0.15 and p = 0.10). CONCLUSIONS: CRVE decreased after CEA, showing that venules constrict after the mechanical hindrance of blood flow is removed. Higher grades in arteriolar and venular tortuosity in the macula, a potential ocular biomarker of CS, subsided after CEA.

Cross-Talk Between Large Artery Stiffness and Retinal Microvasculature in Children: The ExAMIN Youth SA Study.

Background: Cross-talk between the macro-and microvasculature is considered an important contributor to target organ damage. Previous findings were predominantly in adult populations and investigation into this mechanism in children may provide insight into the development of early adverse vascular changes. Whether any ethnic differences in cross-talk is evident, also remains to be determined. Objective: To determine whether retinal microvascular diameters are associated with large artery stiffness in young children and whether ethnic differences are evident. Materials and Methods: In this cross-sectional study, 730 black (n = 437) and white (n = 293) school children aged 5-9 years were included. Pulse wave velocity (PWV) was measured and the central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) diameters were calculated from fundus images. The arterio-venous ratio (AVR) was subsequently calculated. Results: Pulse wave velocity was lower (p ≤ 0.001) in the black group when compared to the white group. The black group had a narrower CRAE, wider CRVE and lower AVR (all p < 0.001). Pulse wave velocity associated negatively with CRAE (r = -0.141, p = 0.003) and AVR (r = -0.185, p ≤ 0.001) in the black group only. A positive association between PWV and CRVE was seen in the black (r = 0.174, p ≤ 0.001) and white (r = 0.119, p = 0.043) group. Conclusion: Large artery stiffness is associated with retinal arterial narrowing and venular widening in children, suggesting cross-talk between the macro-and microvasculature. Ethnic differences in these associations are also evident. Our findings warrant further investigation into environmental and sociocultural risk factors contributing to premature cardiovascular disease development.

Ocular Blood Volume Index Based on Scattering Properties of Retinal Vessels Using Spectral Domain Optical Coherence Tomography.

Introduction: The evaluation of retinal vessels and the retinal blood flow is important for ocular diseases. We introduce a spectral domain optical coherence tomography (SD-OCT) based method for facilitating a retinal blood vessel analysis using the scattering properties of retinal vessels. The intensity of the distal shadow of vessels caused by the scattered signal is measured, correlated with the pulsatile ocular blood flow (POBF), and its repeatability is analyzed. Methods: About 20 eyes of 20 healthy, young participants (mean age 23.15 years, standard deviation 2.3 years) were included in the analysis. Participants underwent ophthalmic diagnostics including three repeated SD-OCT examinations and measurement of POBF. The vessel shadow intensity analysis is based on peripapillary SD-OCT scans and automatically analyses the intensity of the distal vessel shadow compared to its surroundings. Results: The distal shadow of arteries in SD-OCT scans correlated with the POBF (r = 0.647, p = 0.002). Furthermore, the shadow intensity correlated with the established morphological arterio-venous ratio. The evaluation of repeatability was performed using the interclass correlation coefficient (ICC), showing good repeatability for individual vessels (ICC = 0.825) and arteries (ICC = 0.820). Conclusions: In summary, we indicate that the scattering properties of retinal vessels in SD-OCT images might correlate with the vessel morphology and for retinal arteries with the retinal blood flow volume as well. Further studies are needed to establish this method's sensitivity and specificity in participants with retinal and cardiovascular diseases.

Comparison of subjective and objective methods to determine the retinal arterio-venous ratio using fundus photography.

PURPOSE: To assess the inter and intra observer variability of subjective grading of the retinal arterio-venous ratio (AVR) using a visual grading and to compare the subjectively derived grades to an objective method using a semi-automated computer program. METHODS: Following intraocular pressure and blood pressure measurements all subjects underwent dilated fundus photography. 86 monochromatic retinal images with the optic nerve head centred (52 healthy volunteers) were obtained using a Zeiss FF450+ fundus camera. Arterio-venous ratios (AVR), central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) were calculated on three separate occasions by one single observer semi-automatically using the software VesselMap (ImedosSystems, Jena, Germany). Following the automated grading, three examiners graded the AVR visually on three separate occasions in order to assess their agreement. RESULTS: Reproducibility of the semi-automatic parameters was excellent (ICCs: 0.97 (CRAE); 0.985 (CRVE) and 0.952 (AVR)). However, visual grading of AVR showed inter grader differences as well as discrepancies between subjectively derived and objectively calculated AVR (all p<0.000001). CONCLUSION: Grader education and experience leads to inter-grader differences but more importantly, subjective grading is not capable to pick up subtle differences across healthy individuals and does not represent true AVR when compared with an objective assessment method. Technology advancements mean we no longer rely on opthalmoscopic evaluation but can capture and store fundus images with retinal cameras, enabling us to measure vessel calibre more accurately compared to visual estimation; hence it should be integrated in optometric practise for improved accuracy and reliability of clinical assessments of retinal vessel calibres.

Comparison of two non-mydriatic fundus cameras to obtain retinal arterio-venous ratio.

PURPOSE: To analyze device-dependent variability of two non-mydriatic fundus cameras to obtain arterio-venous ratio (AVR), central retinal arteriolar equivalent (CRAE), and central retinal venular equivalent (CRVE) in static vessel analysis (SVA). METHODS: We examined 53 participants (29 men, 24 women; median age 46 years) of the Study of Health in Pomerania (SHIP). We took 45° optic-disc-centered fundus images of the right eye with two different non-mydriatic fundus cameras. The first photograph was obtained from the TRC-NW 200, the second from the OCT 2000 (both Topcon Corporation, Tokyo, Japan). One experienced grader graded image quality from 1 "ideal quality" to 5 "not analyzable" and determined AVR, CRAE, and CRVE with the software Vesselmap3 (Imedos, Jena, Germany). RESULTS: Average image quality was 1.8 for the TRC-NW 200 and 1.6 for the OCT 2000. AVR could not be determined in 5 images of the TRC-NW 200 due to low image quality, while six images of the OCT 2000 were not analyzable. The difference between AVR taken from two different non-mydriatic cameras was 0.01 ± 0.03 in Bland-Altman plots. The difference between CRAE was 0.17 ± 10.15 and between CRVE was -2.32 ± 11.76. CONCLUSIONS: The two different non-mydriatic cameras showed good agreement with respect to image quality. When using the same reading software, AVR, CRAE, and CRVE agreed well. Thus, funduscopy and SVA seem to be robust against inter-device variability. As a result, device dependency can remain unconsidered in follow-up examinations with different technical equipment. However, variability might impact more with devices from different manufacturers.