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Maziyar M Khansari, Justin Wanek, Nicole Camardo, Mahnaz Shahidi; Automated Assessment of Hemodynamics in the Conjunctival Microvascular Network. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1971.
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© ARVO (1962-2015); The Authors (2016-present)
Conjunctival microcirculation is accessible for direct visualization and can provide information about microvascular hemodynamics properties of the eye and other organs of the body. This study reports a method for automated assessment of hemodynamics in the conjunctival microvascular network.
Multiple image sequences of the conjunctival microcirculation were acquired in one eye of 10 healthy human subjects (age; 48 + 8 years). In 5 subjects, the same area of the conjunctiva microcirculation was imaged repeatedly. Variance filtering was used to automatically segment vessels in which red blood cell motion was detectable. Diameter (D) and axial blood velocity (V) were measured and blood flow (Q) and wall shear rate (WSR) were calculated from D and V. These measurements were categorized into 4 diameter (<15 μm, 15-24 μm, 25-34 μm, >34 μm) and 4 velocity groups (<0.2 mm/s, 0.2-0.4 mm/s, 0.4-0.6 mm/s, >0.6mm/s). Measurement repeatability was assessed by the standard deviation of repeated measurements. General linear model multivariate analysis was performed to determine the effects of D (or V) group and vessel type on D, V, Q and WSR. Significance was accepted at P < 0.01 to correct for multiple comparisons.
Compiled data yielded D and V measurements in 75 arterioles and 240 venules. The largest number of measurements were obtained in the 15-24 μm and 25-34 μm D groups (for venules and arterioles), and in the < 0.2 mm/s and 0.2-0.4 mm/s (for arterioles) and > 0.6 mm/s (for venules) V groups. In arterioles and venules, D and Q were significantly different among D groups (P ≤ 0.005), but V and WSR were similar among D groups (P ≥ 0.03). As expected, in both arterioles and venules, V, Q and WSR were significantly different among V groups (P < 0.001), but D was similar among V groups (P > 0.06). The repeatability of D and V measurements were 1 μm and 0.09 mm/s, respectively. In both arterioles and venules, V was not linearly correlated with D (P = 0.2), while Q was linearly correlated with D (P < 0.001). WSR was linearly correlated with D in arterioles (P = 0.007), but not in venules (P = 0.03).
An automated method for quantitative and comprehensive assessment of hemodynamics of the conjunctival microvascular network was demonstrated. This method may be useful for detection of microvascular hemodynamic alterations due to systemic and ocular diseases.
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