Effect of Carbogen, Oxygen and Intraocular Pressure on Heidelberg Retina Flowmeter Parameter ‘Flow’ Measured at the Papilla

Abstract

The aim of the study was to evaluate whether the Heidelberg retina flowmeter (HRF), a new device for retinal and anterior optic nerve blood flow assessment, can gauge, at least semiquantitatively, a known effect such as an increase in optic nerve blood flow by hypercapnia or a decrease in optic nerve blood flow by hyperoxia or high intraocular pressure (IOP). Measurements with the HRF were obtained at the papilla of three groups of 5 young healthy subjects (1) at baseline and after breathing 5% carbogen, (2) at baseline and after breathing 100% oxygen and (3) at baseline and after increasing IOP to 20 and 50 mm Hg. The changes in the value of the HRF parameter ‘flow’ were analyzed by means of a paired Student’s t test. Breathing 100% oxygen for 7 min resulted in a statistically significant decrease of 34.7±2.5% (mean ± SEM) in HR parameter ‘flow’ (p < 0.01) at the papilla. Breathing 5% carbogen for 7 min resulted in a statistically significant increase of 18.3±2.6% in HRF parameter ‘flow’ (p = 0.024). Increasing IOP to 20 mm Hg did not result in a statistically significant change in HRF parameter ‘flow’ (–9.6±7.4%; p = 0.13). Increasing IOP from 20 to 50 mm Hg, however, resulted in a statistically significant decrease of 40.1±6.6% in HRF parameter ‘flow’ (p = 0.003). With the applied stimuli, the HRF parameter ‘flow’ changed in the expected direction, i.e. an increase with hypercapnia and a decrease with hyperoxia or high IOP. The simplicity of use of the HRF instrument suggests that it might be well suited for a non-invasive, at least semiquantitative, assessment of changes in blood flow at the papilla.

The effects of dorzolamide 2% and dorzolamide/timolol fixed combination on retinal and optic nerve head blood flow in primary open-angle glaucoma patients

“…By using non-invasive technologies such as Scanning Laser Doppler Flowmetry (SLDF) and analysis softwares that produce highly reproducible intrasession and intersession results such as the Automatic Full Field Perfusion Image Analyzer software (AFFPIA-SLDF 3.3, G Michelson, Erlangen, Germany), [12][13][14][15][16][17][18] it is possible to accurately assess the haemodynamic effects of antiglaucomatous drugs.…”

Relationship between Blood Flow Velocities in Retrobulbar Vessels and Laser Doppler Flowmetry at the Optic Disk in Glaucoma Patients

“…Therefore, confocal scanning laser Doppler flowmetry has been applied to evaluate optic nerve blood flow in glaucoma patients [17, 18]. In addition, it has been shown that the HRF can detect a known effect such as an increase in optic nerve blood flow by hypercapnia or a decrease in optic nerve blood flow by hyperoxia or high intraocular pressure [20]. The present study suggests that blood flow velocities in retrobulbar vessels might be of relevance for optic nerve blood flow.…”

“…HRF parameters were computed within a square of 50 × 50 pixels (window of measurement). This was chosen because previous results had demonstrated that, with such a window of measurement, HRF can detect a known effect such as an increase in optic nerve blood flow by hypercapnia or a decrease in optic nerve blood flow by hyperoxia or high intraocular pressure [20]. …”

Ocular haemodynamic responses to induced hypercapnia and hyperoxia in glaucoma

“…In order to test the hypothesis that vasospasm underlies some cases of glaucoma, the known vasodilative effects of hypercapnia 9-12 and vasoconstrictive effects of hyperoxia [12][13][14][15] were used to stimulate autoregulatory responses in the retrobulbar vasculature of normal subjects and glaucoma patients. It was proposed that if the glaucoma patients' vasculature was in a pre-existing reversible vasoconstricted state the glaucoma and normal groups would differ in their response to vasoactive stimuli.…”