Changes in Retinal Blood Flow in Response to an Experimental Increase in IOP in Healthy Participants as Assessed With Doppler Optical Coherence Tomography.

Stefan Puchner,Leopold Schmetterer,Marco Augustin,Gerhard Garhofer,Martin Kallab,René Marcel Werkmeister,Stephan Szegedi,Nikolaus Hommer,Kristina Stjepanek,Rainer Leitgeb,Doreen Schmidl,Laurin Ginner

doi:10.1167/iovs.61.2.33

Abstract

PurposeBlood flow autoregulation is an intrinsic mechanism of the healthy retinal vasculature to keep blood flow constant when ocular perfusion pressure (OPP) is changed. In the present study, we set out to investigate retinal blood flow in response to an experimental decrease in OPP in healthy participants using Doppler optical coherence tomography.MethodsFifteen healthy participants aged between 22 and 31 years (mean, 27 ± 3 years) were included in the present open study. IOP was increased stepwise via the suction cup method to induce a decrease in OPP. Retinal blood flow in arteries and veins was assessed using a custom-built Doppler optical coherence tomography system and pressure–flow relationships were calculated to assess autoregulation.ResultsSuction cup application induced a pronounced increase in IOP with a maximum value of 50.5 ± 8.0 mm Hg at the highest level of suction. Pressure–flow relationships revealed that blood flow was autoregulated until the OPP was decreased by approximately 21 mm Hg and started to decrease significantly when the OPP was reduced by 30 mm Hg. Retinal blood flow at the last suction period decreased at a maximum of –57.0 ± 22.3% and 65.2 ± 15.4% in retinal arteries and retinal veins, respectively. These changes in retinal blood flow were less pronounced than the decrease in OPP (–75.2 ± 19.2%), indicating retinal autoregulation.ConclusionsThe results of the present study confirm that retinal blood flow is autoregulated in response to changes in the OPP. Doppler optical coherence tomography has the potential to become a clinical tool for the investigation of retinal blood flow autoregulation in the future, because of its ability to assess the blood velocities and diameter of the retinal vessels parallel and therefore also their blood flow in absolute values. (Clinicaltrials.gov number NCT03398616)

Highlights

Blood flow autoregulation is an intrinsic mechanism of the healthy retinal vasculature to keep blood flow constant when ocular perfusion pressure (OPP) is changed
These changes in retinal blood flow were less pronounced than the decrease in OPP (–75.2 ± 19.2%), indicating retinal autoregulation
The results of the present study confirm that retinal blood flow is autoregulated in response to changes in the OPP

Summary

Methods

Fifteen healthy participants aged between 22 and 31 years (mean, 27 ± 3 years) were included in the present open study. The present study was performed in adherence to the Declaration of Helsinki and the Good Clinical Practice guidelines of the European Union. During the 4 weeks before the first study day, a screening examination was carried out that included recording of medical history, a pregnancy test in females of childbearing potential, and a full ophthalmologic examination (bestcorrected visual acuity, slit lamp examination, measurement of IOP and indirect fundoscopy). In the 3 weeks before the first study day and during the course of the study, no blood donation and no intake of concomitant medication was allowed, except contraceptives. During the week after completion of the study, a follow-up safety ophthalmologic examination was performed

Results

Discussion

Conclusion