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F. Tayyari, S.T. Venkataraman, T. Wong, C. Hudson; The Relationship Between Retinal Vascular Reactivity and Arteriolar Diameter . Invest. Ophthalmol. Vis. Sci. 2006;47(13):479.
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To determine the relationship between the magnitude of retinal vascular reactivity and arteriolar diameter using the Canon Laser Blood Flowmeter (CLBF). Two secondary aims were to determine: a) the repeatability of the vascular reactivity measurements and b) if there are any order effects in terms of provoking vasoconstriction or vasodilation first.
The sample comprised 6 healthy, young subjects (mean age 26.5 years, SD 4.04). Each subject attended for three sessions. The first session was used to determine eligibility and select hemodynamic measurement sites. At sessions 2 and 3, O2 and CO2 were sequentially administered to the subjects using a face mask and sequential re–breathing circuit (to maintain standardized hyperoxia and hypercapnia). The order of vasoconstriction and vasodilation was varied across sessions 2 and 3. Measurements of vessel diameter, centerline blood velocity and derived blood flow were acquired at baseline and during stabilized vasoconstriction and vasodilation at two discrete measurements sites along the supero–temporal arteriole.
The baseline diameters for the narrower and wider measurement sites along the supero–temporal arteriole were 90.0µm (SD 15.2) and 115.8µm (SD 12.6), respectively (paired t–test p<0.0001). In response to hypercapnia, the group mean change in diameter at the narrower site was +7.5% (SD 6.9) and at the wider measurement site was +3.0% (SD 1.9). In response to hyperoxia, the group mean change in flow at the narrower site was –18.1% (SD 5.4) at the wider site was –10.6% (SD 2.5). In response to hypercapnia, the group mean change in flow at the narrower site was +28.0% (SD 15.0) and at the wider measurement site was +22.2% (SD 13.4). In response to hyperoxia, the group mean change in flow at the narrower site was –48.9% (SD 6.6) at the wider site was –35.7% (SD 11.4).
In response to standardized provocation, narrower measurement sites demonstrate a greater change in retinal vascular reactivity than wider measurement sites along the same arteriole.
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