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Michel Paques, Kiyoko Nakashima, Florence Rossant, Jose A. Sahel; Structural analysis of small vessels In The Human Retina : an adaptive optics study. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5655.
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Small arteries and veins form a complex, multifunctional network which, beside blood flow distribution, plays a pivotal role in hemodynamic homeostasis and in cellular and metabolic exchanges. Morphological changes affecting the wall of small arteries are surrogates of end-organ damage due to aging, diabetes and/or hypertension, yet these changes have not been directly observed in vivo in humans since fundus photographs only allows viewing the red cell column. Here, we analyzed the structure of retinal vessels in humans using adaptive optics (AO) imaging.
The retinal vessels of 5 healthy subjects, 5 arterial hypertensive patients and one uveitis patient were analyzed by computerized analysis of infrared (850nm) AO images (rtx1 camera; ImagineEye, Orsay, France).
On AO images the wall of small arteries (inner diameter ~ 50-150 µm) could be resolved. Composite imaging allowed reconstruction of vessel pathways over several millimeter length. In healthy, normotensive subjects, the wall-to-lumen ratio (WLR) ranged from 19 to 23% and was not correlated to diameter. Branching topology of arterioles was in general agreement with the principle of minimal work down to the 3rd branching order. The wall of veins could not be clearly identified. Age and hypertension were accompanied by an increase of WLR (up to 40%) and by an increased incidence of local irregularities of the lumen diameter. In the uveitis patient, AO objectivated thickening of both arterial and venous walls.
Because of its ability to resolve the wall of small vessels, AO fundus imaging offers a unique opportunity for investigating fundamental and clinical aspects of the human microcirculation. Our finding of a concomitant increase of WLR and lumen irregularities during aging and hypertension challenges the classic concept of distinct eutrophic versus hypertrophic remodeling of the wall of small arteries. Other diseases affecting vessels such as diabetes and vasculitis may also benefit from AO imaging.
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