Abstract
Abstract Purpose To compare subfoveal choroidal blood flow (ChBF) in sitting and supine position in normal volunteers. Methods ChBF was measured with laser Doppler flowmetry in 22 healthy volunteers (mean age ± SD: 24 ± 5 years). Six independent measurements of choroidal blood flow were obtained in one randomly selected eye of each subject. Subsequently, the subjects assumed a supine position for 30 minutes and a new series of 6 measurements was obtained. Parallel hereto, systemic blood pressure and intraocular pressure were measured. Ocular perfusion pressure (OPP) was calculated based on formulas derived from ophthalmodynamometric studies. The influence of changing OPP on the change in ChBF was assessed in a linear regression analysis. Results The coefficient of variation for ChBF was 10.28% and 9.58% in the sitting and the supine position respectively. ChBF decreased by 6.6% (p=0.0017) in the supine position. The estimate for ophthalmic blood pressure in the supine position was adjusted to obtain a result of no change in OPP for no change in ChBF, yielding an average decrease for the estimate of OPP of 6.7% (p=0.0002). Change in OPP correlated significantly with change in ChBF (R2: 0.20; p=0.036) with a slope for the regression line of 1.04. Conclusion The comparable degree of change in ChBF and OPP and the linear relationship between the two parameters suggest a passive response of the choroidal circulation to the posture change. In contrast, the OPP estimates suggest a marked buffering of the change in perfusion pressure by the carotid system, compatible with a close control of the gradient in perfusion pressure between the heart and its branches within the carotid system.
Published Version
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