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Ebrahimi SM, Tuunanen J, Saarela V, Honkamo M, Huotari N, Raitamaa L, Korhonen V, Helakari H, Järvelä M, Kaakinen M, Eklund L, Kiviniemi V. Synchronous functional magnetic resonance eye imaging, video ophthalmoscopy, and eye surface imaging reveal the human brain and eye pulsation mechanisms. Sci Rep 2024; 14:2250. [PMID: 38278832 PMCID: PMC10817967 DOI: 10.1038/s41598-023-51069-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 12/30/2023] [Indexed: 01/28/2024] Open
Abstract
The eye possesses a paravascular solute transport pathway that is driven by physiological pulsations, resembling the brain glymphatic pathway. We developed synchronous multimodal imaging tools aimed at measuring the driving pulsations of the human eye, using an eye-tracking functional eye camera (FEC) compatible with magnetic resonance imaging (MRI) for measuring eye surface pulsations. Special optics enabled integration of the FEC with MRI-compatible video ophthalmoscopy (MRcVO) for simultaneous retinal imaging along with functional eye MRI imaging (fMREye) of the BOLD (blood oxygen level dependent) contrast. Upon optimizing the fMREye parameters, we measured the power of the physiological (vasomotor, respiratory, and cardiac) eye and brain pulsations by fast Fourier transform (FFT) power analysis. The human eye pulsated in all three physiological pulse bands, most prominently in the respiratory band. The FFT power means of physiological pulsation for two adjacent slices was significantly higher than in one-slice scans (RESP1 vs. RESP2; df = 5, p = 0.045). FEC and MRcVO confirmed the respiratory pulsations at the eye surface and retina. We conclude that in addition to the known cardiovascular pulsation, the human eye also has respiratory and vasomotor pulsation mechanisms, which are now amenable to study using non-invasive multimodal imaging of eye fluidics.
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Affiliation(s)
- Seyed-Mohsen Ebrahimi
- Oulu Functional NeuroImaging (OFNI), Diagnostic Imaging, Medical Research Center (MRC), Finland Oulu University Hospital, 90029, Oulu, Finland.
- Research Unit of Health Sciences and Technology (HST), Faculty of Medicine, University of Oulu, 90220, Oulu, Finland.
| | - Johanna Tuunanen
- Oulu Functional NeuroImaging (OFNI), Diagnostic Imaging, Medical Research Center (MRC), Finland Oulu University Hospital, 90029, Oulu, Finland
- Research Unit of Health Sciences and Technology (HST), Faculty of Medicine, University of Oulu, 90220, Oulu, Finland
| | - Ville Saarela
- Department of Ophthalmology and Medical Research Center, Oulu University Hospital and Research Unit of Clinical Medicine, University of Oulu, Oulu, Finland
| | - Marja Honkamo
- Department of Ophthalmology and Medical Research Center, Oulu University Hospital and Research Unit of Clinical Medicine, University of Oulu, Oulu, Finland
| | - Niko Huotari
- Oulu Functional NeuroImaging (OFNI), Diagnostic Imaging, Medical Research Center (MRC), Finland Oulu University Hospital, 90029, Oulu, Finland
- Research Unit of Health Sciences and Technology (HST), Faculty of Medicine, University of Oulu, 90220, Oulu, Finland
| | - Lauri Raitamaa
- Oulu Functional NeuroImaging (OFNI), Diagnostic Imaging, Medical Research Center (MRC), Finland Oulu University Hospital, 90029, Oulu, Finland
- Research Unit of Health Sciences and Technology (HST), Faculty of Medicine, University of Oulu, 90220, Oulu, Finland
| | - Vesa Korhonen
- Oulu Functional NeuroImaging (OFNI), Diagnostic Imaging, Medical Research Center (MRC), Finland Oulu University Hospital, 90029, Oulu, Finland
- Research Unit of Health Sciences and Technology (HST), Faculty of Medicine, University of Oulu, 90220, Oulu, Finland
| | - Heta Helakari
- Oulu Functional NeuroImaging (OFNI), Diagnostic Imaging, Medical Research Center (MRC), Finland Oulu University Hospital, 90029, Oulu, Finland
- Research Unit of Health Sciences and Technology (HST), Faculty of Medicine, University of Oulu, 90220, Oulu, Finland
| | - Matti Järvelä
- Oulu Functional NeuroImaging (OFNI), Diagnostic Imaging, Medical Research Center (MRC), Finland Oulu University Hospital, 90029, Oulu, Finland
- Research Unit of Health Sciences and Technology (HST), Faculty of Medicine, University of Oulu, 90220, Oulu, Finland
| | - Mika Kaakinen
- Oulu Center for Cell-Matrix Research, Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Lauri Eklund
- Oulu Center for Cell-Matrix Research, Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Vesa Kiviniemi
- Oulu Functional NeuroImaging (OFNI), Diagnostic Imaging, Medical Research Center (MRC), Finland Oulu University Hospital, 90029, Oulu, Finland.
- Research Unit of Health Sciences and Technology (HST), Faculty of Medicine, University of Oulu, 90220, Oulu, Finland.
- Oulu Center for Cell-Matrix Research, Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Oulu, Finland.
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Felder AE, Rahimi M, Nankali A, Matei N, Abdolahi F, Blair NP, Shahidi M. A retinal imaging system for combined measurement of optic nerve head vascular pulsation and stimulated vasodilation in humans. Sci Rep 2023; 13:17149. [PMID: 37816947 PMCID: PMC10564928 DOI: 10.1038/s41598-023-44390-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Accepted: 10/07/2023] [Indexed: 10/12/2023] Open
Abstract
Vascular pulsation at the optic nerve head (ONH) reflects vessel properties. Reduction in the stimulated retinal vasodilatory capacity has been reported in diabetes, but its relation with vascular pulsation is unknown. Here we report a new retinal imaging system for correlative assessment of ONH vascular pulsation and stimulated retinal vasodilation. Retinal reflectance images were acquired before and during light flicker stimulation to quantify arterial and venous vasodilation (DAR, DVR) in subjects with and without diabetic retinopathy (N = 25). ONH vascular pulsation amplitude and frequency (PA, PF), were quantified by curve fitting of periodic intensity waveforms acquired in retinal vasculature (RV) and ONH tissue (ONHT) regions. The relationships between pulsation metrics, heart rate (HR), intraocular pressure (IOP), and vasodilatory responses were evaluated. Pulsation metrics were not significantly different between regions (p ≥ 0.70). In RV, inter-image variabilities of PA and PF were 10% and 6%, whereas inter-observer variabilities were 7% and 2% respectively. In both regions, PF was correlated with HR (p ≤ 0.001). PA was associated with DAR in both regions (p ≤ 0.03), but only with DVR in RV (p ≤ 0.05). Overall, ONH vascular pulsation was associated with stimulated retinal vasodilation, suggesting diabetes may have concomitant effects on retinal vasculature compliance and neurovascular coupling.
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Affiliation(s)
- Anthony E Felder
- Richard and Loan Hill Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, IL, USA
| | - Mansour Rahimi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, 90033, USA
| | - Amir Nankali
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, 90033, USA
| | - Nathanael Matei
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, 90033, USA
| | - Farzan Abdolahi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, 90033, USA
| | - Norman P Blair
- Department Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, 90033, USA.
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Tornow RP, Odstrcilik J, Kolar R. A multi-color video-ophthalmoscopes allows to measure the spectral distribution of light absorption of blood in the human retina. Front Med (Lausanne) 2023; 10:1125154. [PMID: 37007778 PMCID: PMC10060599 DOI: 10.3389/fmed.2023.1125154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 02/24/2023] [Indexed: 03/18/2023] Open
Abstract
Based on our previously developed mono-color video-ophthalmoscope a multi-color video-ophthalmoscope was developed. Using narrow band transmission filters, this instrument allows to measure the pulsatile cardiac cycle induced blood volume changes in the human retina for any wavelength in the sensitivity range of the used CMOS-camera. In this key experiment, video sequences (8 s, 25 fps, 200 frames) of the optic nerve head (ONH) were acquire for seven wavelengths between 475 nm and 677 nm one after the other. After image registration of all frames of each video sequence (to compensate for eye movements) and trend correction (to compensate for slow intensity changes), the amplitude of the cardiac cycle induced light intensity changes (pulsatile absorption amplitude PAA) can be calculated for all seven wavelengths. The results confirmed that the spectral distribution of PAA (λ) follows the distribution of the light absorption of blood. The measured values correspond to the absorption of a thin blood layer of about 0.5 μm thickness.
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Affiliation(s)
- Ralf-Peter Tornow
- Department of Ophthalmology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
- *Correspondence: Ralf-Peter Tornow,
| | - Jan Odstrcilik
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czechia
| | - Radim Kolar
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czechia
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Odstrcilik J, Kolar R, Horn F, Tornow RP. Comparative analysis of retinal photoplethysmographic spatial maps and thickness of retinal nerve fiber layer. PLoS One 2023; 18:e0284743. [PMID: 37146019 PMCID: PMC10162550 DOI: 10.1371/journal.pone.0284743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 04/01/2023] [Indexed: 05/07/2023] Open
Abstract
The paper presents a comparative study of the pulsatile attenuation amplitude (PAA) within the optic nerve head (ONH) at four different areas calculated from retinal video sequences and its relevance to the retinal nerve fiber layer thickness (RNFL) changes in normal subjects and patients with different stages of glaucoma. The proposed methodology utilizes processing of retinal video sequences acquired by a novel video ophthalmoscope. The PAA parameter measures the amplitude of heartbeat-modulated light attenuation in retinal tissue. Correlation analysis between PAA and RNFL is performed in vessel-free locations of the peripapillary region with the proposed evaluating patterns: 360° circular area, temporal semi-circle, nasal semi-circle. For comparison, the full ONH area is also included. Various positions and sizes of evaluating patterns in peripapillary region were tested which resulted in different outputs of correlation analysis. The results show significant correlation between PAA and RNFL thickness calculated in proposed areas. The highest correlation coefficient Rtemp = 0.557 (p<0.001) reflects the highest PAA-RNFL correspondence in the temporal semi-circular area, compared to the lowest value in the nasal semi-circular area (Rnasal = 0.332, p<0.001). Furthermore, the results indicate the most relevant approach to calculate PAA from the acquired video sequences is using a thin annulus near the ONH center. Finally, the paper shows the proposed photoplethysmographic principle based on innovative video ophthalmoscope can be used to analyze changes in retinal perfusion in peripapillary area and can be potentially used to assess progression of the RNFL deterioration.
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Affiliation(s)
- Jan Odstrcilik
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
| | - Radim Kolar
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
| | - Folkert Horn
- Department of Ophthalmology, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Germany
| | - Ralf-Peter Tornow
- Department of Ophthalmology, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Germany
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Kolar R, Vicar T, Odstrcilik J, Valterova E, Skorkovska K, Kralik M, Tornow RP. Multispectral retinal video-ophthalmoscope with fiber optic illumination. JOURNAL OF BIOPHOTONICS 2022; 15:e202200094. [PMID: 35604408 DOI: 10.1002/jbio.202200094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/17/2022] [Accepted: 05/18/2022] [Indexed: 06/15/2023]
Abstract
Multispectral imaging is used in various applications including astronomy, industry and agriculture. In retinal imaging, the single-shot multispectral image stack is typically acquired and analyzed. This multispectral analysis can provide information on various structural or metabolic properties. This paper describes the multispectral improvement of a video-ophthalmoscope, which can acquire retinal video sequences of the optic nerve head and peripapillary area using various spectral light illumination. The description of the multispectral video imaging is provided and several applications are described. These applications include multispectral retinal photoplethysmography, visualization of spontaneous vein pulsation and multispectral RGB image generation.
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Affiliation(s)
- Radim Kolar
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
| | - Tomas Vicar
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
| | - Jan Odstrcilik
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
| | - Eva Valterova
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
| | - Karolina Skorkovska
- Department of Ophthalmology and Optometry, St. Ann University Hospital, Brno, Czech Republic
- Department of Ophthalmology and Optometry, Masaryk University, Brno, Czech Republic
| | - Martin Kralik
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
| | - Ralf-Peter Tornow
- Department of Ophthalmology, Friedrich-Alexander-University Erlangen-Nürnberg, Germany
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Abstract
Theoretical models of retinal hemodynamics showed the modulation of retinal pulsatile patterns (RPPs) by heart rate (HR), yet in-vivo validation and scientific merit of this biological process is lacking. Such evidence is critical for result interpretation, study design, and (patho-)physiological modeling of human biology spanning applications in various medical specialties. In retinal hemodynamic video-recordings, we characterize the morphology of RPPs and assess the impact of modulation by HR or other variables. Principal component analysis isolated two RPPs, i.e., spontaneous venous pulsation (SVP) and optic cup pulsation (OCP). Heart rate modulated SVP and OCP morphology (pFDR < 0.05); age modulated SVP morphology (pFDR < 0.05). In addition, age and HR demonstrated the effect on between-group differences. This knowledge greatly affects future study designs, analyses of between-group differences in RPPs, and biophysical models investigating relationships between RPPs, intracranial, intraocular pressures, and cardiovascular physiology. Video-recordings of retinal pulsatile patterns in human eye are modulated by heart rate and age. This invivo evidence fundamentally impacts modeling of retinal function and clinical design in wide range of medical specialties.
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Kolář R, Odstrčilík J, Tornow RP. Photoplethysmographic analysis of retinal videodata based on the Fourier domain approach. BIOMEDICAL OPTICS EXPRESS 2021; 12:7405-7421. [PMID: 35003842 PMCID: PMC8713668 DOI: 10.1364/boe.441451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 10/22/2021] [Accepted: 10/22/2021] [Indexed: 05/23/2023]
Abstract
Assessment of retinal blood flow inside the optic nerve head (ONH) and the peripapillary area is an important task in retinal imaging. For this purpose, an experimental binocular video ophthalmoscope that acquires precisely synchronized video sequences of the optic nerve head and peripapillary area from both eyes has been previously developed. It enables to compare specific characteristics of both eyes and efficiently detect the eye asymmetry. In this paper, we describe a novel methodology for the analysis of acquired video data using a photoplethysmographic approach. We describe and calculate the pulsatile attenuation amplitude (PAA) spatial map, which quantifies the maximum relative change of blood volume during a cardiac cycle using a frequency domain approach. We also describe in detail the origin of PAA maps from the fundamental (the first) and the second harmonic component of the pulsatile signal, and we compare the results obtained by time-based and frequency-based approaches. In several cases, we show the advantages and possibilities of this device and the appropriate image analysis approach - fast measurement and comparison of blood flow characteristics of both eyes at a glance, the robustness of this approach, and the possibility of easy detection of asymmetry.
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Affiliation(s)
- Radim Kolář
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, 616 00 Brno, Czech Republic
| | - Jan Odstrčilík
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, 616 00 Brno, Czech Republic
| | - Ralf-Peter Tornow
- Department of Ophthalmology, Friedrich-Alexander-University of Erlangen-Nuremberg, 91056 Erlangen, Germany
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Labounkova I, Labounek R, Nestrasil I, Odstrcilik J, Tornow RP, Kolar R. Blind Source Separation of Retinal Pulsatile Patterns in Optic Nerve Head Video-Recordings. IEEE TRANSACTIONS ON MEDICAL IMAGING 2021; 40:852-864. [PMID: 33232226 DOI: 10.1109/tmi.2020.3039917] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Dynamic optical imaging of retinal hemodynamics is a rapidly evolving technique in vision and eye-disease research. Video-recording, which may be readily accessible and affordable, captures several distinct functional phenomena such as the spontaneous venous pulsations (SVP) of central vein or local arterial blood supply etc. These phenomena display specific dynamic patterns that have been detected using manual or semi-automated methods. We propose a pioneering concept in retina video-imaging using blind source separation (BSS) serving as an automated localizer of distinct areas with temporally synchronized hemodynamics. The feasibility of BSS techniques (such as spatial principal component analysis and spatial independent component analysis) and K-means based post-processing method were successfully tested on the monocular and binocular video-ophthalmoscopic (VO) recordings of optic nerve head (ONH) in healthy subjects. BSSs automatically detected three spatially distinct reproducible areas, i.e. SVP, optic cup pulsations (OCP) that included areas of larger vessels in the nasal part of ONH, and "other" pulsations (OP). The K-means post-processing reduced a spike noise from the patterns' dynamics while high linear dependence between the non-filtered and post-processed signals was preserved. Although the dynamics of all patterns were heart rate related, the morphology analysis demonstrated significant phase shifts between SVP and OCP, and between SVP and OP. In addition, we detected low frequency oscillations that may represent respiratory-induced effects in time-courses of the VO recordings.
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