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Jake Hillard, Toco Chui, Dan Sapir, Thomas Gast, Stephen Burns; Adaptive Optics Measurements of Retinal Arterial Wall Thickness in both Normotensive and Hypertensive Subjects. Invest. Ophthalmol. Vis. Sci. 2013;54(15):6061.
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To make precise measurements of vascular wall thickness in the retinas of both systemically normotensive and hypertensive individuals using an adaptive optics scanning laser ophthalmoscope (AOSLO).
We used the Indiana AOSLO, operated with a relatively large (10x the Airy disc) confocal aperture, displaced by more than the Airy disc radius. This imaging approach provides excellent imaging of the retinal vasculature, and gives a better visualization of the walls (Chui et al 2012). Images of retinal blood vessels ranging from capillaries to the largest retinal vessels were obtained in a group of 6 normal subjects and 16 subjects with a history of hypertension. Vessels ranging in size from an inner diameter of 9 to 171 microns were measured. Measurements were made using an image editing program and were repeated on each vessel 5 times. The lumens of the vessels were differentiated from the vessel walls by the motion of erythrocytes, within the lumens, readily seen on aligned video sequences.
Arterial walls and lumens were able to be measured in all subjects and in almost all of the vessels chosen for analysis. Venous walls were occasionally measurable in hypertensive but not in normal subjects. Some arteries could not be measured due to shadowing or focusing in a different plane although all tested individuals had at least some measurable arteries. For both small arteries and arterioles (lumen diameters < 50 microns) and larger ones, the hypertensive subjects had higher wall to lumen ratios (p< 0.02 , p<0.03 ) respectively. The highest ratios occurred for the smallest vessels in the hypertensive subjects (Figure 2).
We have been able to measure arterial wall thickness in vessels with lumen diameters as small as 9 microns using an AOSLO. The imaging technique used allows clear visualization of the vessel walls which can be used to precisely measure arterial wall thickness non-invasively in subjects with a history of hypertension.
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