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E. A. Polska, J. Kolodjaschna, C. Simader, F. Berisha, K. Karl, A. Luksch, G. Fuchsjaeger-Mayrl, L. Schmetterer; Limits of Choroidal Autoregulation in Healthy Humans. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2267.
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The aim of this study was to evaluate physiologic autoregulatory capacity of the human choroid during changes in ocular perfusion pressure using data from studies previously performed in our lab.
The lower and upper limits of choroidal autoregulation were studied in healthy male non-smokers, 19 - 35 years old. Intraocular pressure was artificial elevated using the suction cup method. A change in systemic arterial blood pressure was induced by isometric exercise (squatting). Choroidal blood flow was assessed using laser Dopler flowmetry. Intraocular pressure was measured with an applanation tonometer. Mean brachial artery blood pressures (MAP) were measured on the upper arm by an automated oscillometric device. Ocular perfusion pressure was calculated as 2/3MAP - IOP. The main outcome parameter was the relationship between ocular perfusion pressure and choroidal blood flow. Data from eight different studies were collected. Only data obtained during periods without any drugs were included.
The suction cup was applied to eighty three volunteers. During an artificial IOP rise the choroid maintains its blood flow almost constant up to 30% reduction in ocular perfusion pressure. Ninety six subjects performed squatting. During isometric exercise the upper limit of autoregulation appears to be approximately 60% above the baseline ocular perfusion pressure.
The choroid is able to maintain its blood flow almost constant during wide range of ocular perfusion pressure. However, relatively large inter-individual differences could be observed. Moreover, changes in choroidal circulation were sooner dependent on IOP values and showed only little association with MAP.
retrospective analysis of data
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