This is a single-center, prospective, and cross-sectional study.
The study was carried out in accordance with the principles of the Declaration of Helsinki after obtaining ethical consent from the Kafkas University, Medicine Faculty, Ethics Committee with the number 80576354-050-99/158. A total of 76 patients that presented to Kafkas University Faculty of Medicine Department of Ophthalmology between July 2019 and March 2020 and were diagnosed with RVO and 76 controls were included in the study. A consent form was received from all patients that they would participate in the study.
The detailed ophthalmological examinations of the patients with RVO were performed. The best-corrected visual acuity (BCVA) and the logarithmic equivalents of the minimum resolution angle (logMAR) were determined. In all cases, the anterior segment and fundus examination findings were recorded. The patients' RVO type (CRVO or RVBO) was recorded. The central macular thicknesses at the time of presentation were evaluated by optical coherence tomography (RTVue 100-2; Optovue, Fremont, CA, USA). In addition, the patients' body mass index (BMI) was calculated, and the presence of diabetes mellitus, hypertension, hyperlipidemia, CAD, and smoking was noted.
All venous blood samples were taken from the antecubital vein after 12 hours of fasting. Hemoglobin (Hgb), hematocrit (Htc), sodium (Na), potassium (K), AST, ALT, urea, total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), and some biochemical parameters, such as C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and D-dimer level were evaluated.
Ultrasonic Evaluation of Endothelial Function
FMD and Pulse Wave Velocity (PWV) Measurement:
Brachial artery B-mode ultrasonography examinations were performed by a single radiologist (T.Ç.) blinded to the ocular examination findings and personal data of the patients, using an ultrasound system (Siemens Acuson S3000, Siemens Healthcare GmbH Henkestr. 127 91052 Erlangen/Germany). The images were digitally recorded and interpreted offline. Endothelial dysfunction was detected by applying the FMD technique to the brachial artery. The procedure was performed according to the guidelines published by Coretti et al., following a 12-hour fasting period in a quiet room at 22-25 °C.9
Alcoholic or caffeinated beverages were prohibited for 12 hours before the procedure. The patients were placed in a comfortable position on their back. The transducer was placed on the right brachial artery trace 4-5 cm above the elbow and longitudinally visualized in the region where there was no tortuosity, and the best image was taken during the course of the artery. In order to standardize the measurement site, the measurement was undertaken 5 cm above the antecubital fossa, covering a 5-7 cm artery segment. The brachial artery diameter (intima to intima) was measured three times, and the average of these three values was recorded as the basal diameter. The cuff of the sphygmomanometer was attached to the arm and inflated at an average pressure of 250 mmHg and held for five minutes before being suddenly lowered, and PWV was measured in 15 seconds. The brachial artery diameter was recorded at the first and second minutes after the hyperemic response to evaluate FMD. The maximum diameter in these measurements was used in FMD calculations. FMD was calculated as a %increase compared to the basal vessel diameter using the formula, “FMD = [(MD - BD) / BD] x 100”.
Ultrasonographic Evaluation of Carotid Arteries
Carotid artery B-mode ultrasonography examinations were performed by a single radiologist (T.Ç.) blinded to the patients’ ocular examination findings and personal data, using an ultrasound system (Siemens Acuson S3000, Siemens Healthcare GmbH Henkestr. 127 91052 Erlangen/Germany) and a 9L4 linear transducer. The patients were placed on their back with their necks slightly extended, and the transducer was placed transversely in the midline of the neck. By shifting the transducer slightly to the right and left, the carotid arteries were viewed from the transverse section, and the carotid bulb was attempted to be localized. Longitudinal plane images were obtained from both internal carotid arteries (ICAs) of the patients. The lumen-intima and media-adventitia interfaces of the back wall of the carotid arteries were obtained by enhancing the images using the magnification-zoom function of the device. At least five measurements were made from the back wall in each segment, and the mean CIMT measurements of ICAs were taken. The average of these values was used in the statistical analysis.
Aged 45-75 years, having undergone retinal vascular branch or root occlusion, and not having a history of surgical intervention that can affect the function of vascular structures in the neck and arm.
Diabetic retinopathy, hypertensive retinopathy, presence of choroidal neovascular membrane, hepatic or renal insufficiency, history of systemic inflammatory disease (inflammatory connective tissue diseases), acute or chronic infectious (HIV, HBV, and HCV) disease, and pregnancy history.
Statistical evaluations were made using SPSS v. 21.0 (Statistical Package for the Social Sciences, Windows version Chicago, USA), and power analysis was undertaken using the ClinCalc program (Rosner B. Fundamentals of Biostatistics. 7th ed. Boston, MA: Brooks / Cole; 2011. http: // clincalc. com / stats / samplesize.aspx). Type I error (alpha value) 0.05 and power 80% of the study were calculated. While evaluating the study data, descriptive statistics, including the mean, standard deviation, median, frequency, ratio, minimum and maximum values were used. The independent samples t-test and logistic regression analysis were used in the analysis of independent quantitative data. In the analysis of independent qualitative data, the chi-square and binary logistic regression tests were used. Using variables found to be significant in the univariate analysis, a multivariate logistic regression analysis was conducted to identify the independent determinants, which are risk factors for RVO. Statistical significance was accepted as p < 0.05.