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Editors Selection IGR 7-2

Bloodflow: Effect of aging on blood flow

Comment by Alon Harris on:

24978 Effect of aging on retinal circulation in normotensive healthy subjects, Nagaoka T; Sato E; Takahashi A et al., Experimental Eye Research, 2009; 89: 887-891

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USA Aging has been strongly associated with age-related macular degeneration, glaucoma and vascular occlusive disease. Several studies have suggested that both cerebral and ocular blood flow decrease with age.¹

Nagaoka et al. (1513) present interesting data which contributes to this growing field of interest by examining retinal arterioles in 45 normal and pre-hypertensive healthy men. The authors report no statistically significant differences in vessel diameter, blood velocity, retinal blood flow or wall shear rate between subjects with and without pre-hypertension or in association with increasing age. Upstroke time² (UT); however, was found to be different between subjects with and without pre-hypertension and was associated with increasing age. This article contributes to the literature suggesting vascular changes occur with increasing age and suggests UT may be useful in following retinal arteriolar changes associated with aging. The article is uniform in its inclusion of only male non-smokers and is strengthened by the exclusion of topical and systemic medications. However, despite several implications to the concept, the study does not specifically measure any aspect of retinal microcirculation. The author's methodologies² utilizing bi-directional laser Doppler velocimetry are limited to vessels of 60 μm in diameter or larger and include only two seconds of measure in one retinal arteriole for each subject. This greatly diminishes any conclusions of how total retinal blood flow or the retinal microcirculation may be affected by aging. Another important consideration, pre-hypertensive subjects were a decade older (p = 0.06) than non-hypertensive subjects; therefore it is not possible to know if the differences in seen UT between normotensive and pre-hypertensive groups were due to age rather than blood pressure status.

Providing further insight into the ocular vasculature is of ever growing importance in ophthalmic research. Future studies are needed to elucidate how age affects the autoregulation of ocular blood flow in both healthy and diseased patient populations. A comprehensive hemodynamic assessment, examining multiple vascular beds, is also currently suggested to provide the most meaningful understanding of ocular blood flow.³

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