Abstract
The time course of the changes in the optic nerve head (ONH) blood flow in response to changes in the ocular perfusion pressure (OPP) induced by an artificial elevation of the intraocular pressure (IOP) has not been determined. We measured the blood flow, represented by the mean blur rate (MBR), on the ONH determined by laser speckle flowgraphy. The MBR was determined before, during, and after the IOP was elevated by 20 or 30 mmHg by pressure applied on the eye by an ophthalmodynamometer in a total of 27 healthy eyes. For an IOP elevation of 20 mmHg, the percentage reduction in the MBR-vessel was −24.7%, and in the MBR-tissue was −16.0% (P < 0.001). For an IOP elevation of 30 mmHg, the percentage reduction of the MBR-vessel was −35.3% and the MBR-tissue was −24.7% (P < 0.001). During the 30 mmHg IOP elevation for 10 minutes, both the MBR-vessel and MBR-tissue began returning to the baseline level from 1 minute after the beginning of the IOP elevation (P < 0.01, P < 0.05, respectively) and continued returning during the 10 minutes IOP elevation (P < 0.001, P < 0.01, respectively). We conclude that the ONH can autoregulate its blood flow in response to experimental changes in OPP induced by IOP elevations.
Highlights
Autoregulation plays an important role in controlling the blood flow in tissues of the different organs in the body, and autoregulation enables a constant supply of oxygen and nutrients to the tissues to maintain the homeostasis[1]
It is important to know how the optic nerve head (ONH) blood flow responds to continuous intraocular pressure (IOP) elevations
The laser speckle flowgraphy (LSFG) images were recorded at 1 minute before the IOP elevation, immediately after the IOP elevations, and at 20 minutes after the release of the pressure (Figs 2 and 3)
Summary
Autoregulation plays an important role in controlling the blood flow in tissues of the different organs in the body, and autoregulation enables a constant supply of oxygen and nutrients to the tissues to maintain the homeostasis[1]. Autoregulation of the ocular blood flow in response to changes in the intraocular pressure (IOP) has been investigated by various methods and in different species[1,2]. The autoregulation of the blood flow on the ONH during changes in the ocular PP (OPP) by increases in the IOP with a constant mean ophthalmic artery pressure has been investigated[3,4,5,6,7,8]. The level of the OPP below which autoregulation in the ONH breaks down has been different in these different experimental studies These earlier studies have mainly focused on whether autoregulation was present and its functional range. The clinical use of this technique is limited because it is time-intensive
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