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P. A. Rose, C. Hudson; The Impact of Age on Retinal Vascular Reactivity and the Relationship With Cardiovascular Risk Factors. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2266.
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To investigate the impact of aging on retinal vascular reactivity and systemic levels of cardiovascular risk factors in healthy subjects.
The sample comprised 63 healthy subjects ranging in age from 21 to 66 years (20 males; 46 females). Non-invasive hemodynamic measurements (diameter, velocity and flow) were collected from superior temporal retinal arterioles and venules using the Canon Laser Blood Flowmeter (CLBF, model 100) before, during and after exposure to hyperoxia. Isocapnia was maintained using a previously validated sequential rebreathing circuit. Blood pressure, heart rate, respiration rate, and inspired and expired oxygen and carbon dioxide levels were monitored using a critical care monitor. Fasting blood levels of cholesterol, triglycerides, blood glucose and high sensitivity C-reactive protein (CRP) were measured in all subjects. Hemodynamic parameters were analyzed using repeated measures ANOVA; correlations among outcome measures were analyzed using univariate and multivariate regression models (Statistica Software). Results were considered statistically significant at p<0.05.
Hyperoxia significantly decreased retinal arteriolar and venular diameter, blood velocity and flow across all age groups. The magnitude of arteriolar constriction was significantly reduced with increase in age (p=0.045). Arteriolar constriction decreased by 0.16 µm annually between the ages of 22 and 66 years. CRP was positively correlated with baseline and hyperoxic arteriolar diameter, blood velocity and flow (r value range 0.29 to 0.49; p value range 0.0487 to 0.0003). Cholesterol and triglyceride levels were correlated with venular blood velocity (r=0.34, p=0.0171 and r=0.41, p=0.0034, respectively).
Retinal arteriolar constriction decreased with increase in age in clinically healthy subjects. Further, retinal arteriolar hemodynamic parameters were significantly correlated with blood levels of CRP, a marker of peripheral vascular disease. Studies are ongoing to elucidate the nature of the relationship between CRP and retinal hemodynamics.
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