Retinal Arterial Diameter Research Articles

Association Between Risk Factors and Glaucomatous Damage in Untreated Primary Open-angle Glaucoma

To analyze an association between the presumed risk factors for glaucoma and the actual extent of glaucomatous damage in untreated primary open-angle glaucoma. In 50 untreated open-angle glaucoma patients, we analyzed an association between the level of glaucomatous damage and presumed glaucoma risk factors: mean untreated intraocular pressure (IOP) and short-term IOP variability, ocular pulse amplitude, corneal thickness, acral and corneal temperature, retinal arterial diameter and retinal venous diameter, choroidal blood flow (laser Doppler flowmetry flow, velocity, volume), heart rate, and ocular perfusion pressure. Morphologic damage (mean retinal nerve fiber layer thickness, measured by ocular coherence tomography) and functional damage (visual field mean defect) were evaluated separately in 2 forward-stepwise multiple regression models. The mean retinal nerve fiber layer thickness was significantly (P<0.05) associated with IOP (r=-0.35), retinal arterial diameter (r=0.36), and choroidal blood flow (r=0.30); mean defect was associated with ocular perfusion pressure (r=-0.30), laser Doppler flowmetry volume (r=-0.33), and IOP variability (0.36). Despite small differences between the morphologic and functional glaucomatous damage, IOP and perfusion parameters seem to contribute, at least in part, independently to both.

Relationship between Retinal Vascular Caliber and Coronary Artery Disease in Patients with Non-Alcoholic Fatty Liver Disease (NAFLD)

Objective: To evaluate the relationship between retinal vascular caliber and cardiovascular disease in non-alcoholic fatty liver disease (NAFLD) patients without diabetes and hypertension. Methods: Intention to treat study of individuals who underwent cardiac computed tomography (CT) during a two year period. Coronary artery disease (CAD) was defined as stenosis of >50% in at least one major coronary artery. Liver and spleen density were measured by abdominal (CT); intima-media thickness (IMT) by Doppler ultrasound; retinal artery and vein diameter by colored-retinal angiography; and metabolic syndrome by ATP III guidelines. Serum biomarkers of insulin resistance, inflammation, and oxidant-antioxidant status were assessed. Results: Compared with 22 gender and age matched controls, the 29 NAFLD patients showed higher prevalence of coronary plaques (70% vs. 30%, p < 0.001), higher prevalence of coronary stenosis (30% vs. 15%, p < 0.001), lower retinal arteriole-to-venule ratio (AVR) (0.66 ± 0.06 vs. 0.71 ± 0.02, p < 0.01), higher IMT (0.98 ± 0.3 vs. 0.83 ± 0.1, p < 0.04), higher carotid plaques (60% vs. 40%, p < 0.001), higher homeostasis model assessment of insulin resistance (HOMA) (4.0 ± 3.4 vs. 2.0 ± 1.0, p < 0.005), and higher triglyceride levels (200 ± 80 vs. 150 ± 60, p < 0.005) than controls. Multivariate analysis showed fatty liver (OR 2.5; p < 0.01), IMT (OR 2.3 p < 0.001), and retinal AVR ratio (OR 1.5, p < 0.01) to be strongly associated with CAD independent of metabolic syndrome (OR 1.2, p < 0.05). Conclusions: Patients with smaller retinal AVR (<0.7) are likely to be at increased risk for CAD and carotid atherosclerosis in patients with NAFLD even without hypertension or diabetes.

Retinal Pulse Wave Velocity in Young Male Normotensive and Mildly Hypertensive Subjects

Hypertension is characterized by microvascular remodeling resulting in increased wall/lumen ratio and elevated microvascular stiffness. Aiming to transform the measurement of macrovascular stiffness into a microvascular environment we introduce a noninvasive method to assess rPWV. rPWV alterations in early hypertension are investigated in detail. The developed methodology is compared with its possible computational alternatives. Time dependent alterations of retinal arterial diameter were assessed noninvasively by the DVA in 65 male normoalbuminuric normotensive to mildly hypertensive subjects (age: 28.7 ± 6.0 years). rPWV was computed using three different methods. "Method 1" used filtration at HR, "Method 2" filtered at higher HR multiples, and "Method 3" used in addition, linear fit for data averaging. "Method 2" and "Method 3" applying filtration at high HR multiples showed strong associations with systolic BP throughout the cohort (r = 0.49, r = 0.63, p < 0.001). Based on the highest association, "Method 3" was proposed to characterize rPWV. Hypertensive patients showed higher rPWV (1243 ± 694 RU/sec) than subjects with high-normal BP (786 ± 486 RU/sec, p < 0.01) or normotensive subjects (442 ± 148 RU/sec, p < 0.001). rPWV demonstrated a strong association with BP and can discriminate between optimal, high-normal, and mildly hypertensive BP values. rPWV may add detailed insights into early microvascular pathophysiology, potentially beyond microalbuminuria.

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Calculation of central retinal artery diameters from non‐invasive ocular haemodynamic measurements in type 1 diabetes patients

The aim of the study was to compare the diameter of the central retinal artery (CRA) between patients with diabetes mellitus and healthy subjects in vivo. CRA diameters were calculated from retinal haemodynamic parameters measured with noninvasive measurement techniques. Sixteen patients with type 1 diabetes with no or mild diabetic retinopathy and 16 age-matched healthy controls were included in this study. Total retinal blood flow was assessed by combining bidirectional laser Doppler velocimetry in all veins entering the optic disc with measurements of retinal vessel diameters using a Dynamic Vessel Analyser. Blood flow velocity in the CRA was measured with colour Doppler imaging (CDI). The diameter of the CRA in the optic nerve was then calculated for each subject using the individual ocular haemodynamic data. Calculated CRA diameters were significantly larger in patients with diabetes (180 ± 13 μm) compared with healthy controls (166 ± 10 μm, p = 0.001). No significant differences were found in retinal blood flow, retinal artery or vein diameters or mean flow velocity of the CRA. The data of the present study show increased calculated CRA diameter in patients with type 1 diabetes with no or mild retinopathy. Blood flow velocity measurements in retrobulbar vessels using CDI need to be interpreted with caution in terms of retinal blood flow, because no information about vessel diameters is obtained by this technique.

Cerebral White Matter and Retinal Arterial Health in Hypertension and Type 2 Diabetes Mellitus

We examined 33 hypertensive (22 with comorbid type 2 diabetes mellitus (T2DM)) and 29 normotensive (8 with T2DM) middle-aged and elderly adults, comparable in age and education. Relative to normotensive participants, those with hypertension, in addition to a higher prevalence of periventricular white matter (WM) lesions, had significantly lower WM microstructural integrity of major fiber tracts as seen with MRI-based diffusion tensor imaging. Among participants with hypertension, those with co-morbid T2DM (n = 22) had more widespread WM pathology than those without T2DM (n = 11). Furthermore and consistent with previous research, both hypertension and T2DM were related to decreased retinal arterial diameter. Further exploratory analysis demonstrated that the observed retinal arteriolar narrowing among individual with hypertension was associated with widespread subclinical losses in WM microstructural integrity and these associations were present predominantly in the frontal lobe. We found that T2DM adds to the damaging effects of hypertension on cerebral WM, and notably these effects were independent of age and body mass index. Given that the decrease in retinal arteriolar diameter may be a biomarker for parallel pathology in cerebral arterioles, our data suggest that the frontal lobe may be particularly vulnerable to microvascular damage in the presence of hypertension and T2DM.

Five-Year Incidence of Age-related Macular Degeneration: The Beijing Eye Study

To examine the incidence of age-related macular degeneration (AMD) and its associated factors in an adult Chinese population. Population-based study. The Beijing Eye Study, which included 4439 subjects (age ≥ 40 years) in 2001, was repeated in 2006 with 3251 (73.2%) subjects participating. Fundus photographs were graded using the International Age-related Maculopathy Epidemiological Study Group grading system. Incidence of AMD. Gradable slides were available on 3049 (93.9%) subjects who participated in the survey of 2001 and again in 2006. The incidence of early, late, and neovascular AMD per eye was 2.6% (95% confidence interval [CI], 2.2-3.0), 0.1% (95% CI, 0.00-0.2), and 0.1% (95% CI, 0.00-0.2), respectively. The incidence of early, late, and neovascular AMD per person was 4.2 ± 0.4% (95% CI, 3.5-5.0), 0.1 ± 0.1% (95% CI, 0.0-0.2), and 0.1 ± 0.1% (95% CI, 0.0-0.2), respectively. By multivariate analysis, incident early AMD was associated significantly with greater age at baseline (P = 0.01; odds ratio [OR], 1.03; 95% CI, 1.01-1.06), smaller optic disc size (P = 0.007; OR, 0.50; 95% CI, 0.30-0.83), smaller scleral spur distance (P = 0.04; OR, 0.59; 95% CI, 0.36-0.98), and hyperopic refractive error (P = 0.057; OR, 1.15; 95% CI, 1.00-1.33), with the latter being significant only marginally. It was not associated with the systemic parameters of gender, body height, body mass index, region of habitation, level of education, profession, smoking, arterial blood pressure, diabetes mellitus, fasting blood concentrations of glucose, triglycerides, high-density or low-density lipoproteins; or the ocular parameters of intraocular pressure, retinal arterial and vein diameters, retinal microvascular abnormalities, amount of nuclear cataract, cortical cataract or subcapsular cataract, pseudophakia, glaucoma, nonglaucomatous optic neuropathy, retinal vein occlusions, size of the beta zone of parapapillary atrophy, or progression of the zone of atrophy during the follow-up from 2001 to 2006. Hyperopia, short interscleral spur distance, and small optic disc size were, beside older age, the main factors associated with incident early AMD. This may point to a small globe size, potentially in relation to a firmly attached vitreous, playing a role in early incident AMD. The authors have no proprietary or commercial interest in any of the materials discussed in this article.

Acute effect of pure oxygen breathing on diabetic macular edema.

Purpose. A small-scale pilot study of the pathophysiology of diabetic macular edema (DME) was made by assessing concomitant changes in macular volume (MV), mean arterial blood pressure (MABP), intraocular pressure (IOP), retinal artery diameter (RAD), and retinal vein diameter (RVD) in response to 120 minutes of pure oxygen breathing. Methods. Eleven eyes of 11 patients with DME were examined at baseline and while breathing pure oxygen for 120 minutes followed by 120 minutes of breathing atmospheric air. Macular volume was determined by optical coherence tomography, retinal trunk vessel diameters by fundus photography, intraocular pressure by pulse-air tonometry, and arterial blood pressure by sphygmomanometry. Results. After initiation of pure oxygen breathing, reductions of 2.6% in RAD (p=0.04) and 11.5% reduction in RVD (p<0.001) were observed while MABP increased by 5.2 mmHg. After resumption of atmospheric air breathing, RAD and RVD rapidly returned to baseline values whereas MABP remained 2.3 mmHg higher than baseline (p=0.04). Macular volume was found to be reduced by 1.2% compared to baseline (p=0.04) at 120 minutes after cessation of pure oxygen breathing and resumption of atmospheric air breathing. Conclusion. These results indicate that the vasomotor response of the retinal arteries alone cannot explain the delayed reduction in macular volume after short course of pure oxygen breathing.

Flicker‐induced retinal vasodilatation is not dependent on complement factor H polymorphism in healthy young subjects

AbstractPurpose We have previously shown that choroidal blood flow regulation in healthy subjects is abnormal in carriers of the CC allele at rs1061170, a complement factor H polymorphism that is closely related to the risk of age‐related macular degeneration. This is compatible with data in complement factor H deficient mice showing abnormal choroidal and retinal vasculature associated with endothelial damage. In the present study we hypothesized that the carriers of CC at rs1061170, which have an increased risk of AMD, already show abnormal retinal blood flow regulation at ages below 35 years.Methods A total of 99 healthy subjects (aged between 19 and 35 years) were included in this study. Flicker‐induced retinal vasodilatation was investigated in arteries and veins using the dynamic vessel analyzer (DVA) and genotyping at rs1061170 was performed.Results Out of the 99 subjects 18 were homocygous for the CC allele, 50 were homocygous for the TT allele and 31 subjects were heterocygous. The response in retinal arteries (p=0.376) and retinal veins (p=0.617) to flicker stimulation was similar between the three studied groups. In addition, the baseline diameters of retinal arteries (p=0.619) and veins (p=0.471) was also comparable between the groups.Conclusion Our data indicate that healthy young carriers of the CC allele at rs1061170 do not show abnormal flicker‐induced vasodilatation in the retina. This is in contrast to our previous results in the choroid, where these individuals have abnormal blood flow regulation. Whether this is due to the differences in vasculature or the difference in the stimulus is unclear.

Effects of topical carteolol on retinal arterial blood flow in primary open-angle glaucoma patients

Our aim was to evaluate the effects of topical carteolol on retinal arterial blood flow (RBF) in patients with primary open-angle glaucoma. Sixteen patients received carteolol topically for 90 days. Changes in RBF in the major retinal artery were evaluated using laser Doppler velocimetry at baseline and after 30, 60, and 90 days. Patients were divided into groups based on changes in RBF; retinal arterial blood column diameter, blood velocity, and ocular perfusion pressure (OPP) were compared. Overall, no significant changes in RBF were observed. Twelve patients had unchanged and four decreased RBF. In patients with unchanged RBF, no significant changes in diameter, velocity, and OPP were observed. In patients with decreased RBF, the diameter did not change significantly; velocity decreased from baseline on day 90 (p = 0.041); OPP did not change significantly, but the values on days 30, 60, and 90 were lower than in patients with unchanged RBF. Although carteolol preserved RBF, some patients had decreased RBF with low blood pressure, suggesting that carteolol decreases RBF in some patients with decreased ocular perfusion after the topical instillation of carteolol.

Comparison of retinal vasodilator and constrictor responses in type 2 diabetes

The retinal blood vessels provide a unique way to directly examine the human microvasculature, which is frequently damaged in individuals with diabetes. Previous studies have demonstrated that retinal flickering light-induced vasodilation and hyperoxia-induced vasoconstriction may operate by enhancing or reducing similar vasoregulatory factor(s), but a comparison between these two provocative stimuli in individuals with diabetes has not been studied. The purpose of the study was to examine the association between retinal flickering light-induced vasodilation and retinal hyperoxia-induced vasoconstriction in type 2 diabetic subjects and in healthy controls. Twenty men and women with type 2 diabetes and 10 men and women without diabetes between 21 and 75 years of age were recruited. Changes in retinal artery and vein diameters to flickering light and during hyperoxia (100% oxygen) stimuli were measured on the same visit using a noninvasive retinal imaging device (Dynamic Vessel Analyzer, Imedos Inc., Germany). Compared with controls, diabetic subjects had impaired arterial vasodilator and vasoconstrictor responses to both flickering light and hyperoxia, respectively (both p<0.001). Merging both groups, an inverse correlation (r=-0.56; p=0.003) between the retinal artery's responses to flickering light-induced vasodilation and hyperoxia-induced vasoconstriction was demonstrated independent of glucose or insulin levels. This suggests that both responses are attenuated to a similar degree in diabetic subjects and that the attenuation to both stimuli can be observed in retinal arteries and veins. This would suggest that similar vasoregulatory factor(s) might in part help to explain the retinal diameter responses between the two stimuli. One suggested common vasoregulator of vascular tone is nitric oxide; however, other factor(s) may be involved, which contribute to this association and require further research.

Effect of NO synthase inhibition on retinal vessel reaction to isometric exercise in healthy humans

It has been shown that retinal blood flow is autoregulated, meaning that flow is independent of perfusion pressure within a certain range. We tested the hypothesis that nitric oxide (NO) synthase inhibition alters the response of retinal arterial and venous vessels during isometric exercise. In this study, nine healthy subjects were included. Each subject received the NO synthase inhibitor Ng-monomethyl-l-Arginine (l-NMMA, the α-receptor agonist phenylephrine or placebo intravenously on three study days. Retinal vessel diameter was assessed with the retinal vessel analyser (RVA), at baseline and during a squatting period of 6-7 min in absence or presence of l-NMMA, phenylephrine or placebo. Mean arterial pressure (MAP) and pulse rate (PR) increased significantly during all pretreatment squatting periods (p < 0.001) Retinal venous and arterial diameters showed a continuous decrease during squatting (p < 0.001). Phenylephrine increased MAP and PR but did not alter the retinal vessel diameter response to squatting. Administration of l-NMMA lead to a significant decrease in venous diameter before isometric exercise (p = 0.004). In addition, the retinal venous diameter response during administration of the NO synthase inhibitor was less pronounced than during phenylephrine or placebo (p < 0.001). Our study confirms that NO plays an important role in the control of retinal vascular tone at rest. In addition, the present data indicate a role of NO in retinal autoregulation, because the response of retinal venous diameters was altered after NO synthase inhibition. The nature of involvement, however, appears to be complex and requires further studies.

Abstract 3802: Retinal Vasoreactivity as a Marker of Impaired Cerebral Function in Diabetes

The eye and the brain share embryological, anatomic and physiological similarities, which suggest that the retinal microvasculature may be an ideal surrogate marker of cerebrovascular function. This is intriguing, as the cerebral vasculature cannot be directly measured in a non-invasive manner. In epidemiological studies abnormal retinal Arteriovenous Ratios (AVR) are associated with an increased risk of stroke and cerebrovascular disease. However, the association between retinal vasoreactivity measurements and cerebral blood vessel function remains unknown. An attenuated retinal vasoreactivity may indicate endothelial dysfunction in the eye and brain and may prove to be useful as a marker of cerebrovascular disease in high risk populations such as in diabetics. STUDY GOALS: To examine 1) the impact of diabetes at different disease stages on measures of cerebrovascular function and 2) the relationship between retinal blood vessel reactivity, retinal AVRs and measures of cerebral small vessel function. METHODS: This cohort study included 29 type 2 diabetics, 14 pre-diabetics, and 14 healthy controls (ages: 37 to 75 years). Retinal vasoreactivity was measured with the Dynamic Vessel Analyzer (Imedos, Jena, Germany) following high frequency flicker light stimulation. Cerebrovascular blood flow velocity of the Middle Cerebral Artery (MCA) was assessed by Transcranial Doppler Ultrasound (TCD) (Siemens, USA). RESULTS: Progression of diabetes was found to be significantly associated with attenuation of light flicker stimulus response (P=0.0009 artery, P=0.0001 vein, CI 95%), AVR (P=0.0070, CI 95%), PI (P=0.0202, CI 95%), RI (P=0.0033, CI 95%) and hyperventilation-breath hold (P≤0.0001, CI 95%). Across all groups, attenuated retinal arterial and venous diameter responses to the light flicker stimulus were associated with an increase in MCA RI (P=0.02, r=-0.30 artery, P=0.06, r=-0.24 vein, CI 95%). An attenuated venous diameter response was associated with an increase in PI (P=0.02, r=-0.29 vein, CI 95%). In addition, attenuated retinal diameter responses were also associated with a decrease in MCA mean flow velocities following hyperventilation-breath hold (P=0.05, r=0.26 artery, P=0.01, r=0.34 vein, CI 95%). Attenuated retinal responses were also correlated with a reduction in AVR (P=0.05, r=0.26 artery, P=0.15, r=0.19 vein, CI 95%). CONCLUSION: Impairment of retinal vasoreactivity is associated with cerebrovascular dysfunction across the continuum of diabetes, possibly indicating that the eye reflects changes in cerebral blood vessel function and stroke risk.

Changes in the retinal vessel diameter, retinal nerve fiver layer thickness, and optic disc after vitrectomy

AbstractPurpose To investigate the retinal vascular caliber, retinal nerve fiver layer thickness, and optic disc changes in patients after pars plana vitrectomy.Methods We examined 40 eyes in 40 patients who had undergone unilateral pars plana vitrectomy at before and 3 months, 6 months after operation. The diameters of central retinal arteries and veins were measured on retinal photographs. The central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were calculated using the revised Parr‐Hubbard formula. Retinal nerve fiver layer thickness was obtained using Stratus optical coherence tomography. Cup‐to‐disc vertical ratios of optic disc was evaluated using stereo optic disc photoResults There were no significant differences between both eyes before operation. Cup‐to‐disc vertical ratios of optic disc significantly increased for 3 months and 6 months post‐operatively (p&lt;0.01, p&lt;0.01) and there was significant difference between operation eye and fellow eye at the same period (p&lt;0.01, p&lt;0.01). The changes of CRAE and CRVE in operation eye were significantly larger than fellow eye at 6 months post‐operatively (p&lt;0.01, p&lt;0.01). The retinal nerve fiver layer thickness showed no significant changes.Conclusion Whereas no retinal nerve fiver layer thickness decrease was observed, vitrectomy induced changes in Cup‐to‐disc vertical ratios of optic disc and retinal vessel diameter for significant periods following surgery.

Calculation of central retinal artery diameters in patients with type 1 diabetes using non‐invasive measurements

AbstractPurpose To compare the diameter of the central retinal artery between patients with type 1 diabetes and healthy control subjects in vivo. Central retinal artery diameters were calculated from results of non‐invasive measurements of ocular hemodynamics.Methods 16 patients with type 1 diabetes with no or mild diabetic retinopathy and 16 age‐matched healthy controls were participated in this study. Total retinal blood flow was assessed by the use of laser Doppler velocimetry and measurement of retinal vessel diameters in all veins entering the optic disc using a Dynamic Vessel Analyzer. In addition blood flow velocity in the retrobulbar central retinal artery was measured using color Doppler imaging. The diameter of the central retinal artery was then calculated individually for each subject using the obtained ocular hemodynamic data.Results Calculated central retinal artery diameters were significantly larger in patients with diabetes (180 ± 13 µm) compared to healthy controls (166 ± 10 µm, p = 0.001). There were no significant differences in retinal blood flow, retinal vessel diameters or mean flow velocity in the central retinal artery between the two groups.Conclusion The present results indicate a dilation of the central retinal artery in patients with type 1 diabetes, whereas total retinal blood flow is unaltered compared to healthy controls. Results from blood flow velocity measurements using color Doppler imaging in retrobulbar vessels do not include information about vessel diameters and need to be interpreted with caution in terms of retinal blood flow.

Screening for Retinal Vessel Caliber and Its Association with Metabolic Syndrome in Japanese Adults

Retinal microvasculature provides a direct means to assess microvascular health in vivo. We examined whether retinal vessel caliber is associated with the presence of metabolic syndrome in Japanese adults in a health screening program. We examined 1,003 Japanese adults through the health screening program conducted at the Shinoda General Hospital. Retinal vessel caliber was measured from digital fundus images using validated, semiautomated computer-assisted software. Metabolic syndrome was defined according to the definition proposed by the Joint Interim Statement in 2009. Cross-sectional associations between retinal vascular caliber and metabolic syndrome or its individual components were determined as odds ratios (ORs) using multiple logistic regression models. The overall prevalence of metabolic syndrome in the study sample was 29.9%. Persons with increased waist circumference and elevated triglycerides and blood pressure had significantly narrower retinal arterial diameters. Persons with increased waist circumference also had wider retinal venular diameters. Narrower retinal arterial diameters and wider retinal venular diameters were associated with a higher prevalence of metabolic syndrome (OR per -1 standard deviation (SD) change in arteriolar caliber=2.15, 95% confidence interval (CI) 1.45-3.18; OR per +1 SD change in venular caliber=1.53, 95% CI 1.04-2.26). We observed cross-sectional associations between retinal vessel caliber changes and metabolic syndrome and its components. We demonstrated that retinal vessel caliber assessments are feasible in health screening programs in a timely manner. Further longitudinal studies are warranted to determine whether retinal vessel caliber measurements can be used as noninvasive assessment to evaluate vascular health related to metabolic syndrome and cardiovascular diseases in health screening program.

Effect of regular smoking on flicker induced retinal vasodilatation in healthy subjects

BackgroundHabitual smoking is a risk factor for a variety of vascular diseases, including ocular pathologies. In the current study, we set out to investigate whether the regulation of retinal vascular tone is impaired in habitual smokers. For this purpose, vascular reactivity was tested during flicker light induced vasodilatation in smokers and in a non-smoking control group. MethodsIn this prospective, balanced, parallel group study 24 chronic smokers (28.1±3.3years) and 24 age-matched never-smoking volunteers (28.2±4.0years) were included. Flicker induced vasodilatation was measured in major retinal arteries and veins using a retinal vessel analyzer and flicker induced changes in retinal blood velocities were assessed in retinal veins by laser Doppler velocimetry. Three flicker periods of 60s were scheduled. Blood cotinine concentration was determined and a Fagerstrom questionnaire was performed to evaluate nicotine dependency. ResultsIn non-smoking subjects, stimulation with flicker light increased retinal venous diameter by +7.7±3.1%, +6.9±2.9% and +7.1±2.8% during the three flicker periods, respectively. Flicker induced vasodilatation in veins was significantly diminished in chronic smokers (+4.9±2.4%, +6.3±3.1% and +5.7±3.4%, ANOVA between groups, p=0.032) as compared to the non-smoking control group. Calculated retinal blood flow in the measured veins increased by a maximum of +54±21%, +43±18% and +46±19% during the three stimulation periods in the non-smoking subjects, respectively. The flicker induced increase in retinal blood flow as assessed in the veins was significantly reduced in chronic smokers as compared to the non-smoking control group (+19±16%, +26±14%, +24±13%, ANOVA between groups, p=0.013). In retinal arteries, flicker stimulation increased retinal arterial diameters by 5.2±3.8%, 5.8±4.8% and 5.5±5.6% during the three flicker periods in the non-smoking group. In smokers, the flicker induced arterial vasodilatation was not significantly different compared to non-smokers (4.6±4.1%, 3.8±3.7% and 4.8±3.4%, ANOVA between groups, p=0.4). ConclusionOur data indicate that the flicker induced hemodynamic response of retinal veins is reduced in chronic smokers as compared to age matched healthy volunteers. This supports the hypothesis that chronic smoking leads to vascular dysfunction in the eye.

Retinal Vessel Diameter, Retinal Nerve Fiber Layer Thickness, and Intraocular Pressure in Korean Patients With Normal-Tension Glaucoma

To investigate the retinal vessel diameter and evaluate the relationship of the retinal nerve fiber layer (RNFL) thickness with retinal vessel diameter and intraocular pressure (IOP) in patients with normal-tension glaucoma (NTG). A prospective, cross-sectional study. This study included 60 previously untreated patients with NTG (60 eyes) and 45 age- and sex-matched healthy controls (45 eyes) that had no history of systemic vascular disease at a single institution. The diameters of the central retinal arteries and veins were measured on retinal photographs. The central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were calculated using the revised Parr-Hubbard formula. The RNFL thickness was measured using Stratus optical coherence tomography. The mean central retinal arteriolar (P = .000) and venular (P = .000) diameters were significantly smaller in the eyes with NTG than in the normal eyes. Multivariate linear regression analysis demonstrated a significant positive correlation between the RNFL thickness and CRAE (P = .014), and a negative correlation between the RNFL thickness and IOP (P = .005) in the eyes with NTG. However, there was no significant correlation between the RNFL thickness and the independent variables in the control group (P = .112). The patients with NTG had smaller diameters of the central retinal vessels than the normal subjects. Both IOP and CRAE were significantly associated with RNFL thickness in the patients with NTG. Our results suggest that narrower retinal vessels and higher IOP may be related to the thinning of the RNFL in patients with NTG.

Studying hypertension in ocular fundus images using Hausdorff dispersion ordering

Retinal arterial and vein diameters are altered in individuals at risk of cardiovascular events mainly due to high blood pressure. The measurement of retinal vessel diameters has been proved to reflect individuals' vascular health. Dispersion of such measures which are obtained by means of ocular fundus images is a major factor not usually considered in clinical research. In this paper, a method to evaluate if different levels of clinically relevant covariables induce greater dispersion in retinal arterial and vein diameters is proposed. A multivariate dispersion ordering, the Hausdorff dispersion order, is used to compare the level of dispersion in such diameters for different groups of patients. Our statistical conclusions show that dispersion is higher in individuals with long-standing hypertension and in those who need two or more drugs to control hypertension. Hereby, dispersion is increased in the most severely ill persons. However, a greater level of smoking seems to be associated with a lesser dispersion. Dispersion of the vessel diameters must be taken into account in the image analysis of retinal vessel diameters because the comparison between homogeneous groups will produce highly accurate results in medical research.

E0392 Relationship between retinal vasculopathy and coronary artery disease

Background and objectiveStudies showed that atherosclerosis is a systemic disease. Parameters representing peripheral artery atherosclerosis, such as decreased ankle-brachial index (ABI), and increased carotid artery intima-media thickness (CIMT), are well...