Intrinsic imaging of ocular neurovascular coupling in normals and in glaucoma patients
Final Report Abstract
Not only is retinal blood flow reduced in glaucoma, but possibly also the mechanism adjusting it to neuro-retinal activity (neurovascular coupling). This project aimed at developing a technique to image the retinal vascular response to visual stimulation, and to investigate the origin of its impairment. Two instruments were developed: a first one for prototyping, and a second assembled around a clinical Scanning Laser Ophthalmoscope (SLO)/OCT, to which we added photic stimulation and pupil monitoring. Using appropriate procedures to avoid various artifact sources, we examined 43 young healthy subjects. Image analysis procedures, starting with well-known registration algorithms, were then designed to correct for scan artifacts and to analyse functional responses. However, the methodological complexity encountered at this point prevented further studies in glaucomatous subjects, and our work focused on healthy subjects. The retinal reflectance showed an unexpectedly good stability during baseline. Reflectance changes, evoked by visual stimulation were clear, validating the feasibility of recording signals related to neural function in-vivo in humans with a near-infrared SLO. While occasional ideal conditions lead to high quality imaging, in too many recordings, the resultant fundus movies contained too much noise. To improve the fundus reflectance signal, we established a Principal Component Analysis (PCA) to disentangle the targeted functional components from noise. Applying the PCA to fundus movies unexpectedly allowed observing – for the first time – minute arterial vessels’ pulsations and identifying details of the spontaneous venous pulsation found at the optic nerve head. We developed algorithms for quantitative vessel diameters analysis, which revealed that the nature of the venous pulsation is more complex than described so far: Different mechanisms are likely at play among individuals. Furthermore, information on the venous outflow resistance in the eye was revealed. This work presents progress towards a quantitative optical tap on the in-vivo retina in humans through computational imaging, toward imaging the retinal function, and results in new understanding of the ocular blood flow presenting potentials for better non-invasive markers of elevated intracranial pressure and vascular related diseases such glaucoma and carotid artery stenosis through the analysis of the pulsation of the vessels.
Publications
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Intricacies of measuring the mfERG's luminance uniformity in direct and Maxwellian viewing. Biomedical Photonics Network Meeting. Lausanne, Switzerland. 2008
Moret F, Lagrèze WA, Bach M
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Intricacies of measuring the mfERG's luminance uniformity in direct and Maxwellian viewing. Int. Soc. for Clinical Eletrophys. of Vision symposium. Morgantown, USA. 2008
Moret F, Lagrèze WA, Bach M
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Cardiac pulsation cancellation in retinal images by Principal Component Analysis. Meeting of German Workgroup Ophthalmic Optics, Schwerte, Germany. 2009
Moret F, Lagrèze WA, Bach M
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Fundus images filtering by Principal Component Analysis. ARVO Abstract: Invest Ophthalmol Vis Sci. 51: E-Abstract nr 1810. 2010
Moret F, Lagrèze WA, Bach M
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Revealing cardiac pulsation of retinal vessels by Principal Component Analysis. Meeting of the German Workgroup Ophthal. Optics, Homburg, Germany. 2010
Moret F, Poloschek CM, Lagrèze WA, Bach M
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(2011) Visualization of fundus vessel pulsation using Principal Component Analysis. Invest Ophthalmol Vis Sci 52:5457–5464
Moret F, Poloschek CM, Lagrèze WA, Bach M
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Visualization of fundus vessel pulsation using Principal Component Analysis. ARVO Abstract:. Invest Ophthalmol Vis Sci. 52: E-Abstract nr 1339. 2011
Moret F, Lagrèze WA, Poloschek CM, Bach M
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Time of Collapse of Spontaneous Venous Pulsation. ARVO Abstract: Invest Ophthalmol Vis Sci. 53: E-Abstract nr 6861. 2012
Moret F, Lagrèze WA, Poloschek CM, Bach M
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Visualization of fundus vessel pulsation using Principal Component Analysis. World Ophthalmol. Congress. Abu Dhabi, United Arab Emirates. 2012
Moret F, Lagrèze WA, Poloschek CM, Bach M
