Abstract
AimIn the present study the response of optic nerve head blood flow to an increase in ocular perfusion pressure during isometric exercise was studied. Based on our previous studies we hypothesized that subjects with an abnormal blood flow response, defined as a decrease in blood flow of more than 10% during or after isometric exercise, could be identified.MethodsA total of 40 healthy subjects were included in this study. Three periods of isometric exercise were scheduled, each consisting of 2 minutes of handgripping. Optic nerve head blood flow was measured continuously before, during and after handgripping using laser Doppler flowmetry. Blood pressure was measured non-invasively in one-minute intervals. Intraocular pressure was measured at the beginning and the end of the measurements and ocular perfusion pressure was calculated as 2/3*mean arterial pressure –intraocular pressure. ResultsIsometric exercise was associated with an increase in ocular perfusion pressure during all handgripping periods (p < 0.001). By contrast no change in optic nerve head blood flow was seen. However, in a subgroup of three subjects blood flow showed a consistent decrease of more than 10% during isometric exercise although their blood pressure values increased. In addition, three other subjects showed a consistent decline of blood flow of more than 10% during the recovery periods.ConclusionOur data confirm previous results indicating that optic nerve head blood flow is autoregulated during an increase in perfusion pressure. In addition, we observed a subgroup of 6 subjects (15%) that showed an abnormal response, which is in keeping with our previous data. The mechanisms underlying this abnormal response remain to be shown.
Highlights
Abnormalities in blood flow autoregulation at the posterior pole of the eye have been implicated in a variety of eye diseases including glaucoma, diabetes and age-related macular degeneration[1,2,3,4,5,6]
We recently reported on the behavior of optic nerve head (ONH) blood flow during both an increase and a decrease of ocular perfusion pressure (OPP) in healthy subjects[17]
No adequate readings of ONH blood flow were obtained and data are presented for 39 subjects only
Summary
Abnormalities in blood flow autoregulation at the posterior pole of the eye have been implicated in a variety of eye diseases including glaucoma, diabetes and age-related macular degeneration[1,2,3,4,5,6]. We recently reported on the behavior of ONH blood flow during both an increase and a decrease of ocular perfusion pressure (OPP) in healthy subjects[17]. In this study we did, observe that there is a wide interindividual variability of this response and we were able to identify a subgroup of subjects with abnormal ONH blood flow autoregulation patterns. In this previous study we used a 6-minutes squatting period to increase blood pressure in order to achieve OPP values above the upper limit (approximately 64 mmHg in the sitting position) of autoregulation
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