Optic Nerve Head Blood Flow Autoregulation during Changes in Arterial Blood Pressure in Healthy Young Subjects

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.

Physical exercise and glaucoma: a review on the roles of physical exercise on intraocular pressure control, ocular blood flow regulation, neuroprotection and glaucoma‐related mental health

“…Autoregulation was also found in the ONH, as evidenced by a 30% increase in OPP, but there was no corresponding increase in ONH blood flow (measured by LDF) after three sessions of 2-min handgripping (Boltz et al 2013c). Boltz et al (2013a) demonstrated that 6 min of squatting increased OPP by 84% and the ONH red cell flux (measured by LDF) by 27%.…”

Optic nerve head blood flow regulation during changes in arterial blood pressure in patients with primary open‐angle glaucoma

“…Sample size calculation was performed according to previous reproducibility data in healthy subjects (Boltz et al. ). The standard variation for ONHBF is approximately 15%.…”

“…The protocol followed the schedule we have previously used in healthy subjects (Boltz et al. ). Dilatation of the pupil of the right eye was obtained with topical tropicamide (Mydriaticum Agepha‐Augentropfen, Vienna, Austria).…”

Pharmacotherapy of Glaucoma

“…33,138 The mechanisms of autoregulation in the human eye are, however, complex and not fully explored. [139][140][141][142][143][144][145][146][147][148] No strategy is currently available to normalize autoregulation in disease states associated with abnormal blood flow regulation in response to changes in perfusion pressure. In addition, the time course of loss of RGCs and decline in blood flow is not fully established.…”