Arteriolar rarefaction in the conjunctiva of human essential hypertensives

Hypertension has been shown to have a component of increased vascular resistance. In general, the terms increased resistance and vasoconstriction have been used interchangeably. This study demonstrates that in the bulbar conjunctiva of human essential hypertensives, the decrease in number of arterioles may be just as significant as the arteriolar constriction. When compared to 12 age and sex matched normotensive controls, 12 untreated essential hypertensives had a 20% reduction in arteriolar density and a 5% decrease in arteriolar diameter. Both of these findings were significant at the 5% level. In a calculated “Poiseuille resistance,” the vessel rarefaction and the vessel constriction would contribute approximately equally to the increased resistance. These findings support the contention that microcirculatory density and caliber should be considered in discussions of alterations of vascular resistance.