Retinal Vessel Diameter Measurements Research Articles

Imaging Assessment of Peripapillary Vessel Diameters in Postmortem Eyes.

Proof of concept of ex vivo retinal vessel diameter measurements in human postmortem eyes. En face near-infrared (IR) images and optical coherence tomography (OCT) of the optic nerve head (ONH) were captured ex vivo with a Heidelberg Engineering Spectralis (Spectralis, version 7.0.4, Image Capture Module, version 1.2.4, Heidelberg Heidelberg, Germany) device, using a custom-made eye chamber holding and positioning the eyes during the image process. Thirty-two formaldehyde-fixated eyes of 16 patients were imaged. In the IR images, two independent graders measured retinal vessel diameters at the intersection of a drawn circle centered on the ONH with diameters of 2.0 mm and 3.4 mm, respectively. The anatomically corresponding measurements between both graders were statistically analyzed using a Wilcoxon signed-rank test. A total of 246 matched measurements of both graders were analyzed across all 32 imaged eyes. Statistically significant differences between the graders were found for arterioles at 2 mm from the ONH. The other measurements did not show statistically significant intergrader differences. The mean values for arteriole diameters were 72.2 µm at 2.0 mm and 61.5 µm at 3.4 mm for grader 1, and 66.4 µm at 2.0 mm and 63.2 µm at 3.4 mm for grader 2. The mean diameter for venules were 75.5 µm at 2.0 mm and 79.3 µm at 3.4 mm for grader 1, and 67.4 µm at 2 mm and 79.1 µm at 3.4 mm for grader 2. To the best of our knowledge, this is the first study to present IR image-based retinal vessel diameters in ex vivo postmortem eyes. Retinal IR/OCT imaging is possible, and measurements are reproducible in formaldehyde-fixated human eyes. Fixation artefacts result in lower image quality, and this can impose challenges in correctly detecting, classifying, and measuring retinal vessels.

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

PurposeTo measure non-invasively retinal venous blood flow (RBF) in healthy subjects and patients with retinal venous occlusion (RVO). MethodsThe 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). ResultsSoftware 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). ConclusionThis AO-LDV prototype offers new opportunity to study RBF in humans and to evaluate treatment in retinal vein diseases.

Methods to measure blood flow and vascular reactivity in the retina.

Disturbances of retinal perfusion are involved in the onset and maintenance of several ocular diseases, including diabetic retinopathy, glaucoma, and retinal vascular occlusion. Hence, knowledge on ocular vascular anatomy and function is highly relevant for basic research studies and for clinical judgment and treatment. The retinal vasculature is composed of the superficial, intermediate, and deep vascular layer. Detection of changes in blood flow and vascular diameter especially in smaller vessels is essential to understand and to analyze vascular diseases. Several methods to evaluate blood flow regulation in the retina have been described so far, but no gold standard has been established. For highly reliable assessment of retinal blood flow, exact determination of vessel diameter is necessary. Several measurement methods have already been reported in humans. But for further analysis of retinal vascular diseases, studies in laboratory animals, including genetically modified mice, are important. As for mice, the small vessel size is challenging requiring devices with high optic resolution. In this review, we recapitulate different methods for retinal blood flow and vessel diameter measurement. Moreover, studies in humans and in experimental animals are described.

The effect of calcium channel blocker (CCB) treatment on retinal and choroidal vessels in a group of hypertensive patients

ABSTRACT Purpose The present study was designed to observe the vasoreactivity in retina and choroid after calcium channel blocker (CCB) treatment in a group of hypertensive patients. Method The study was based on 56 hypertensive patients (56 eyes) and 56 control subjects (56 eyes). Choroidal scans and the measurement of peripapillary retinal vessel diameters was performed at baseline and optical coherence tomography (OCT) scans were also performed at first month . Subfoveal choroidal thickness (SFCT) and the diameters of superior temporal artery (STA), inferior temporal artery (ITA), superior temporal vein (STV), inferior temporal vein (ITV) were compared between the groups. Results The baseline diameters of the STA, ITA were significantly decreased in the patient group compared with the control group (all p < .05). There was a significant increase at first month after the CCB treatment in comparison to baseline measurements (all p < .05). When compared with the controls, the diameter of venules showed a decrease at baseline but was not significant. After the treatment, the diameters of venules were insignificantly increased compared with baseline measurements (p = .178 and p = .275) and there were also no significant differences between the control group and the patient group in first month (all p > .05). The average choroidal thickness measurements of the hypertensive group was lower than the control group (p = .404) and there was a tendency to increase after the treatment (p = .055). Conclusion This study demonstrates that, treatment with CCB seems to improve retinal arteries and has almost no affect on the choroidal thickness in newly diagnosed hypertensive patients.

Short-term effect of angiotensin-converting enzyme inhibitor on retinal vessel diameter in patients with systemic hypertension

Purpose To determine the retinal vessel diameter changes after angiotensin-converting enzyme (ACE) inhibitor treatment in a group of hypertensive patients. Methods This study included 60 treatment-naive hypertensive patients who were treated with ACE inhibitor. Sixty healthy volunteers served as control group. An optical coherence tomography scan protocol including the measurement of peripapillary retinal vessel diameters was performed at baseline and at 1st month. The diameters of superior temporal artery (STA), inferior temporal artery (ITA), superior temporal vein (STV), inferior temporal vein (ITV), superior nasal artery (SNA), inferior nasal artery (INA), superior nasal vein (SNV) and inferior nasal vein (INV) were statistically compared. Results The baseline diameters of the STA, ITA, SNA, and INA were significantly decreased in the patient group compared with the control group (all p < 0.05). There was a significant increase at 1st month after the treatment in comparison to baseline measurements (all p < 0.05). When compared with the controls, only the diameter of SNV showed a significant decrease at baseline (p = 0.031). After the treatment, the diameters of SNV and INV were significantly increased compared with baseline measurements (p = 0.049 and p = 0.035, respectively). There were no significant differences between the control group and the patient group at 1st month (all p > 0.05). Conclusion Short-term treatment with ACE inhibitor led to a significant improvement in the retinal vessel diameters of patients with hypertension.

Hypertrophic remodelling of retinal arterioles in patients with congestive heart failure.

AimsAnalysis of microvascular parameters in the retinal circulation—known to reflect those in the systemic circulation—allows us to differentiate between eutrophic and hypertrophic remodelling of small arteries. This study aimed to examine microvascular changes in patients with congestive heart failure (CHF) and reduced as well as mid‐range ejection fraction.Methods and resultsForty subjects with CHF underwent measurement of retinal capillary flow (RCF), wall‐to‐lumen ratio (WLR), vessel and lumen diameter, wall thickness, and wall cross‐sectional area (WCSA) of retinal arterioles of the right eye by scanning laser Doppler flowmetry (SLDF). Applying a matched pair approach, we compared this group with reference values of age‐matched controls from a random sample in the population of Pilsen, Czech Republic. There was no significant difference in RCF and WLR between the groups (RCF: P = 0.513; WLR: P = 0.106). In contrast, wall thickness and WCSA, indicators of hypertrophic remodelling, were higher in CHF subjects (WT: 15.0 ± 4.2 vs. 12.7 ± 4.2 μm, P = 0.021; WCSA: 4437.6 ± 1314.5 vs. 3615.9 ± 1567.8 μm2, P = 0.014). Similarly, vessel (109.4 ± 11.1 vs. 100.5 ± 14.4 μm, P = 0.002) and lumen diameter (79.0 ± 7.9 vs. 75.2 ± 8.5 μm, P = 0.009) were increased in CHF.ConclusionsIn CHF subjects, we observed hypertrophic remodelling of retinal arterioles indicative of similar changes of small resistance arteries in the systemic circulation. Microvascular structure and function assessed by SLDF may thereby represent a useful, non‐invasive method for monitoring of microvascular damage in patients with CHF and may offer innovative treatment targets for new CHF therapies.

Retinal Vessel Diameter Changes in COVID-19 Infected Patients

ABSTRACT Purpose: To evaluate the longitudinal changes in retinal vessel diameters in patients with coronavirus disease 2019 (COVID-19). Methods: This study included 25 patients with COVID-19 (Group 1) and 25 healthy subjects (Group 2). The diameters of peripapillary temporal and nasal retinal arteries and veins were measured at baseline and at 4 months after remission. Results: The baseline diameters of the inferior temporal vein and the artery were increased in group 1 compared to controls (p = .007 and p = .041, respectively). There was also an increase in the diameters of the inferior and superior nasal veins and arteries in group 1 at baseline (p = .001, p = .019, p = .037, and p = .008, respectively). Retinal vessel diameters decreased after remission in all quadrants in comparison to baseline measurements (all p < .05). Conclusion: Increased retinal vessel diameters were measured in COVID-19 patients during the disease. Measurement of retinal vessel diameters may be a noninvasive method of estimating the vascular risk.

Evaluation of retinal vessel diameter measurement in coronary artery disease

Evaluation of retinal vessel diameter measurement in coronary artery disease

Comparison of retinal vessel diameter measurements from swept-source OCT angiography and adaptive optics ophthalmoscope

Background/imsTo compare the retinal vessel diameter measurements obtained from the swept-source optical coherence tomography angiography (OCTA; Plex Elite 9000, Carl Zeiss Meditec, USA) and adaptive optics ophthalmoscope (AOO; RTX1, Imagine...

Analysis of Foveal and Parafoveal Microvascular Density and Retinal Vessel Caliber Alteration in Inactive Graves' Ophthalmopathy.

Purpose We aimed to evaluate foveal and parafoveal density using optical coherence tomography angiography and the alteration on the retinal vessel diameter in patients with inactive Graves' ophthalmopathy compared to age-matched normal population. Materials and Methods. Patients with inactive Graves' ophthalmopathy (study group) and healthy individuals (control group) were enrolled in the cross sectionally designed study. The optical coherence tomography angiography parameters and retinal vessel diameter measurements were assessed between the study and control groups. Foveal and parafoveal microvascular density in the retina was measured using optical coherence tomography angiography. Retinal artery and vein diameter and artery/vein ratio were assessed for retinal vessel caliber changes. Results Patients with inactive Graves' ophthalmopathy had higher values of intraocular pressure, proptosis, and axial length (P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, Conclusion Optical coherence tomography angiography could be a novel and promising noninvasive diagnostic technique in patients with inactive Graves' ophthalmopathy to detect foveal and parafoveal vessel density changes compared to healthy subjects. The decrease of retinal vessel diameter might be observed in patients with inactive graves ophthalmopathy.

A novel method for retinal vessel segmentation and diameter measurement using high speed video.

Studying dynamic characteristics of retinal vessels, as opposed to static measures, may provide additional insight into pathophysiological changes associated with local and systemic abnormalities such as glaucoma and hypertension. Various approaches have been developed to derive static biomarkers from retinal still images, but not many for dynamic analysis of video sequences. This study presents a novel method for the assessment of time-dependent diameter changes in high-speed videos (125 fps) from the rat retina. The proposed method is composed of a vessel segmentation and a diameter measurement module. The specificity and sensitivity of the segmentation method over 25 images were 95.1% and 97.3% respectively. The mean and standard deviation of the diameter measurement errors were -0.147±0.41 pixels over 100 measurements.

Prophylactic salpingo-oophorectomy & surgical menopause for inherited risks of cancer: the need to identify biomarkers to assess the theoretical risk of premature coronary artery disease

BackgroundSome women with genetic risk of breast and/or ovarian cancer (e.g., BRCA1/2) opt to undergo prophylactic salpingo-oophorectomy (PSO, or surgical removal of the ovaries & fallopian tubes) in order to reduce their risk of cancer. As a consequence, these women experience “surgical menopause” – accompanied by more severe climacteric symptoms that occur in a much shorter time frame. While the risk of coronary artery disease (CAD) rises with menopause, little is known about how the sudden loss of ovarian function from PSO alters the whole-body physiology, and whether it predisposes women to premature CAD.Methods/DesignTo manage CAD risk there is a prerequisite for reliable biomarkers that can help guide risk assessment and therapeutic interventions. To address these needs, this prospective, observational cohort study will evaluate surrogate markers reflective of CAD health in women experiencing surgical menopause after PSO. Twenty women representing each of the following groups will be enrolled over 3 years (total participants = 240): (i) pre-menopausal PSO, (ii) post-menopausal PSO, (iii) pre-menopausal women undergoing other pelvic surgery, and (iv) pre-menopausal controls (no surgery). All participants will provide blood plasma samples pre- and 1, 3, 6, & 12 months post-operatively, with serial samples collectively assessed for measurements of the study’s primary endpoints of interest. These include a hormone profile (estradiol, follicle stimulating hormone (FSH), luteinizing hormone (LH), and progesterone) and both conventional (lipid profile) and novel biomarkers (Heat Shock Protein 27 (HSP27), HSP27-antibodies (HSP27 Ab), proprotein convertase subtilisin/kexin 9 (PCSK9), inflammatory cytokines) of CAD. Another aspect of this study is the measurement and analysis of retinal vessel diameters – an emerging physiological parameter reflective of CAD risk. Finally, a patient engagement exercise will result in the drafting of patient-generated questionnaires that address the well-being and health concerns of these women as they transition through premature menopause and work with our research team to identify and discuss their health priorities.DiscussionThe protocol of our planned study investigating the effects of PSO on CAD is described herein. Characterization of novel CAD markers in women experiencing surgical menopause will yield new insights into the role of the functional ovary in modulating lipid parameters and other CAD risk factors such as HSP27 and HSP27 Ab.

Retinal Oximetry and Vessel Diameter Measurements With a Commercially Available Scanning Laser Ophthalmoscope in Diabetic Retinopathy.

PurposeTo test the hypothesis that retinal vascular diameter and hemoglobin oxygen saturation alterations, according to stages of diabetic retinopathy (DR), are discernible with a commercially available scanning laser ophthalmoscope (SLO).MethodsOne hundred eighty-one subjects with no diabetes (No DM), diabetes with no DR (No DR), nonproliferative DR (NPDR), or proliferative DR (PDR, all had photocoagulation) underwent imaging with an SLO with dual lasers (532 nm and 633 nm). Customized image analysis software determined the diameters of retinal arteries and veins (DA and DV) and central retinal artery and vein equivalents (CRAE and CRVE). Oxygen saturations of hemoglobin in arteries and veins (SO2A and SO2V) were estimated from optical densities of vessels on images at the two wavelengths. Statistical models were generated by adjusting for effects of sex, race, age, eye, and fundus pigmentation.ResultsDA, CRAE, and CRVE were reduced in PDR compared to No DM (P ≤ 0.03). DV and CRVE were similar between No DM and No DR, but they were higher in NPDR than No DR (P ≤ 0.01). Effect of stage of disease on SO2A differed by race, being increased relative to No DM in NPDR and PDR in Hispanic participants only (P ≤ 0.02). Relative to No DM, SO2V was increased in NPDR and PDR (P ≤ 0.05).ConclusionsAlterations in retinal vascular diameters and SO2 by diabetic retinopathy stage can be detected with a widely available SLO, and covariates such as race can influence the results.

Novel Computerized Method for Measurement of Retinal Vessel Diameters.

Several clinical studies reveal the relationship between alterations in the topologies of the human retinal blood vessel, the outcrop and the disease evolution, such as diabetic retinopathy, hypertensive retinopathy, and macular degeneration. Indeed, the detection of these vascular changes always has gaps. In addition, the manual steps are slow, which may be subjected to a bias of the perceiver. However, we can overcome these troubles using computer algorithms that are quicker and more accurate. This paper presents and investigates a novel method for measuring the blood vessel diameter in the retinal image. The proposed method is based on a thresholding segmentation and thinning step, followed by the characteristic point determination step by the Douglas-Peucker algorithm. Thereafter, it uses the active contours to detect vessel contour. Finally, Heron’s Formula is applied to assure the calculation of vessel diameter. The obtained results for six sample images showed that the proposed method generated less errors compared to other techniques, which confirms the high performance of the proposed method.

Adaptive Higuchi's dimension-based retinal vessel diameter measurement.

This paper proposes the use of an adaptive model to measure the width of retinal vessels in fundus photographs. It is based on the hypothesis that the Higuchi's dimension of the cross-section is proportional to the vessel diameter. This approach does not require image segmentation and binarization of the vessels and therefore is suitable for machine based measurements. The model is developed using a synthetic image of the vessel of known diameter and added noise. As a first step, the vessel cross-section profiles were manually obtained and analyzed using Higuchi's fractal dimension method. A 3D model was formed using the relationship between Higuchi's dimension, vessel diameter and noise variance. This model was then evaluated using expert annotated REVIEW public database and solved for the vessel diameter for performance evaluation. The result showed a good agreement with state of the art techniques. The model is background noise tolerant, estimates the vessel width with subpixel precision and does not require manual intervention.

Effects of two different doses of intravitreal bevacizumab on subfoveal choroidal thickness and retinal vessel diameter in branch retinal vein occlusion.

To investigate the effects of two different doses of intravitreal bevacizumab on subfoveal choroidal thickness (SFChT) and retinal vessel diameter in patients with branch retinal vein occlusion. An interventional, restrospective study of 41 eyes of 41 patients who had completed 12mo of follow-up, divided into group 1 (1.25 mg of bevacizumab, 21 eyes of 21 patients) and group 2 (2.5 mg of bevacizumab, 20 eyes of 21 patients). Complete ophthalmic examination, fluorescein angiography, enhanced depth imaging optical coherence tomography and measurement of retinal vessel diameter with IVAN software were performed at baseline and follow-up. The SFChT changed from 279.1 (165-431) µm at baseline to 277.0 (149-413) µm at 12mo in group 1 (P=0.086), and from 301.4 (212-483) µm to 300.3 (199-514) µm in group 2 (P=0.076). The central retinal arteriolar equivalent (CRAE) changed from 128.8±11.2 µm at baseline to 134.5±8.4 µm at 12mo in group 1, and from 134.6±9.0 µm to 131.4±12.7 µm in group 2 (P=0.767). The central retinal venular equivalent (CRVE) changed from 204.1±24.4 µm at baseline to 196.3±28.2 µm at 12mo in group 1, and from 205.8±16.3 µm to 194.8±18.2 µm in group 2 (P=0.019). The mean central macular thickness (P<0.05) and average best-corrected visual acuity (BCVA; P<0.05) improved in both groups. Changes in the SFChT are not statistically significant and not different according to the doses of bevacizumab. The CRAE did not show significant change, however, the CRVE showed significant decrease regardless of the dose.

Diagnostic Ability of Retinal Vessel Diameter Measurements in Open-Angle Glaucoma.

To determine the diagnostic ability of retinal vessel diameter (RVD) measurements and the factors related to retinal vascular diameters in patients with open-angle glaucoma (OAG). This retrospective observational study included 145 patients with OAG (63 with high-tension and 82 with low-tension glaucoma) and 60 healthy controls. The central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were measured using the IVAN software version 1.3. Receiver operating characteristic (ROC) curves were obtained for the average retinal nerve fiber layer (RNFL) thickness and RVD indices including CRAE, CRVE, and CRAE/CRVE ratio. Areas under the ROC curves (AUCs), 95% confidence intervals (CIs), and sensitivities at a fixed specificity (>90% and >80%) were calculated. Factors related to CRAE were analyzed by simple and multiple linear regression analyses. Among the RVD indices, the CRAE had the largest AUC for discriminating glaucomatous changes between eyes with glaucoma and those without (0.803; 95% CI, 0.742-0.855). The AUC of CRAE did not significantly differ from that of average RNFL thickness (P = 0.134). However, CRAE showed lower sensitivity than average RNFL thickness at a specificity greater than 90%. Factors significantly associated with CRAE in both simple and multiple linear regression analyses were age, spherical equivalent, average RNFL thickness, presence of diabetes mellitus, and a glaucoma diagnosis (all P ≤ 0.05). The diagnostic ability of CRAE for detecting OAG was good, which was not much worse than that of average RNFL thickness. This finding suggests the potential usefulness of RVD for glaucoma detection.

Optic Disc Detection and Blood Vessel Diameter Estimation in Patients with Diabetics Mellitus, using Digital Color Funds Images

Optic disc detection and retinal vessel diameter measurement are important tasks in the studies of the association of retinal micro vascular disease with ocular effects, such as cerebral atrophy, cognitive decline, stroke, diabetes and hypertension. This work presents an automatic detection of optic disc irregularities, and determines an appropriate region of interest for retinal vessel diameter measurement. We measured the retinal vessel diameters in 44 diabetic and 60 normal images captured from human eye fundus images with three parameters: Main retinal artery equivalents, Main retinal vein equivalents, and artery to vein diameter ratio. The average of the main artery equivalents in patients with diabetes mellitus is 8.48 pixels, and the average of main vein equivalents is 11.63 pixels. The average of main artery equivalents in healthy people is 9.57 pixels and the average of main vein equivalents is 12.03 pixels. The average ratio of arteriole to vein diameter is about 0.75 in patients’ images with diabetes and approximately 0.80 in healthy people. The results show that the average ratio of arteriole to vein diameter in diabetic patients is smaller than that of healthy people.

Retinal vascular and structural dynamics during acute hyperglycaemia.

To compare retinal vascular dynamics during acute hyperglycaemia in patients with type 2 diabetes and healthy volunteers. Twenty-one patients with type 2 diabetes and 27 healthy controls were examined with fundus photographic measurement of retinal vessel diameters, retinal oximetry, macular perfusion velocities and optical coherence tomographic measurement of subfoveal choroidal thickness every 30min during a 3-hr 75g oral glucose tolerance test (OGTT). Patients paused antidiabetic therapy for 1week prior to the OGTT. Plasma glucose (PG) and fluctuations in PG were larger in patients with diabetes (p<0.0001). PG increased significantly 30min after ingestion of glucose (p<0.0001 in both groups). With a delay of 0-120min, the PG increase was followed by increased retinal arterial oxygen saturations and arteriovenous oxygen saturation differences, narrowed retinal veins and increased arteriovenous diameter ratios. No effect of age, gender or diabetes status was observed. Choroidal thickness was transiently reduced in controls and unchanged in patients with diabetes (p=0.021). Macular perfusion velocities increased after 150min in patients with diabetes but not in controls (arterial p=0.059; venous p=0.16). Higher age and diabetes tended to be associated with higher retinal arterial oxygen saturation. The transition from fasting to acute hyperglycaemia is followed, with a delay of up to 2hr, by retinal vascular changes, notably increased oxygen extraction, suggesting an effect of secondary metabolic changes. Retinal responses were similar in patients with type 2 diabetes and controls despite differences in glucose levels. It is necessary to standardize measurement conditions in studies of retinal physiology.

Retinal vessel diameter measurements by spectral domain optical coherence tomography.

To describe a spectral domain optical coherence (OCT)-assisted method of measuring retinal vessel diameters. All Patients with an OCT circle scan centered at the optic nerve head using a Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany) were retrospectively reviewed. Individual retinal vessels were identified on infrared reflectance (IR) images and given unique labels both on IR and spectral domain OCT (SD-OCT). Vessel width and vessel types obtained by IR were documented as ground truth. From OCT, measurements of each vessel, including horizontal vessel contour diameter, vertical vessel contour diameter, horizontal hyperreflective core diameter, and reflectance shadowing width, were assessed. A total of 220 vessels from 13 eyes of 12 patients were labeled, among which, 194 vessels (88 arteries and 65 veins confirmed from IR) larger than 40 microns were included in the study. The mean vessel width obtained from IR was 107.9 ± 36.1 microns. A mean vertical vessel contour diameter of 119.6 ± 29.9 microns and a mean horizontal vessel contour diameter of 124.1 ± 31.1 microns were measured by SD-OCT. Vertical vessel contour diameter did not differ from vessel width in all subgroup analysis. Horizontal vessel contour diameter was not significantly different from vessel width for arteries and had strong or very strong correlation with vessel width for veins. In our study, vertical vessel contour diameter measured by current commercially available SD-OCT was consistent with vessel width obtained by IR with good reproducibility. This SD-OCT based method could potentially be used as a standard measurement procedure to evaluate retinal vessel diameters and their changes in ocular and systemic disorders.