Imaging and quantifying ganglion cells and other transparent neurons in the living human retina

Liu, Zhuolin; Kurokawa, Kazuhiro; Zhang, Furu; Lee, John J.; Miller, Donald T.

doi:10.1073/pnas.1711734114

Cited by 174 publications

(181 citation statements)

References 48 publications

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“…5g). The AO-OCT results are consistent with previous observations showing that averaging per se leads to reduction in speckle contrast in in vivo imaging 24,25 . This reduction was hypothesized to arise from the movements of subcellular organelles whose scattering gives rise to speckle.…”

Section: In Vivo Application Of Apm-ao-oct Reduces Speckle Efficientlsupporting

confidence: 91%

“…Recently, it was also found that averaging of multiple, precisely aligned volumes for in vivo OCT imaging could reduce speckle noise and reveal novel cellular scale structure 24,25 . It was hypothesized that such averaging is effective because of the random movement of sub-PSF size scattering elements in cells.…”

Section: Comparison With Similar Methods Of Speckle Reductionmentioning

confidence: 99%

“…of scatters was responsible for varying the speckle pattern between frames 24,25 . Because this latter method relies on time-dependent variation in the sample microstructure, it is inherently passive and dependent on the underlying time course of the mobile scatters.…”

mentioning

confidence: 99%

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Aperture Phase Modulation with Adaptive Optics: A Novel Approach for Speckle Reduction and Structure Extraction in Optical Coherence Tomography

Zhang

Manna

Miller

et al. 2018

Preprint

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Speckle is an inevitable consequence of the use of coherent light in optical coherence tomography (OCT), and often acts as noise that obscures micro-structures of biological tissue. We here present a novel method of suppressing speckle noise intrinsically compatible with adaptive optics (AO) in OCT system: by modulating the phase inside the imaging system pupil aperture with a segmented deformable mirror, thus producing minor perturbations in the point spread function (PSF) to create un-correlated speckle pattern between B-scans, and further averaging to wash out the speckle but maintain the structures. It is a well-controlled and universal method which can efficiently determine the optimal range of phase modulation that minimizing speckle noise while maximizing image resolution and signal strength for different systems and/or samples. As an active method, its effectiveness and efficiency were demonstrated by both ex-vivo non-biological and in-vivo biological applications. Introduction:Speckle is a long-standing issue in all imaging technologies that use coherent light sources 1-4 , arised from the interference between light scattered by a random distributed scatters inside the system point-spread function (PSF), and observed as voxel-to-voxel intensity fluctuations in the image 5, 6 . Although speckle is a potential useful information about the dynamics of sample microstructure, in most applications it acts as a major noise source that degrades image quality. Optical coherence tomography (OCT) is a volumetric imaging technology developed in 1991 7 . It has been soon adopted in many biomedical applications 8-12 . However, as a method dependent on the coherent properties of light, OCT images suffer from speckle noise [13][14][15] .Many approaches have been taken to suppress speckle, including generation of multiple images by various means with uncorrelated speckle patterns, followed by averaging [16][17][18][19] . A weakness of these methods is that the number of uncorrelated speckle patterns that can be created is typically small, limiting speckle suppression by averaging. Speckle reduction methods using digital post-processing have also been proposed 20-23 . However, digital post-processing usually reduces speckle by spatial averaging or filtering, which necessarily reduces image resolution. Recently, it was shown that simple averaging of suitably numerous, well aligned images can reduce speckle for in vivo imaging, and it was hypothesized that subcellular motility Fig. 1 | System setup (photo in SI: Fig. S2) and the geometry of the segmented deformable mirror. a, OCT sample arm (Inset: (i) -Photo of the DM; (ii) -setup for USAF 1951 resolution test target; (iii)covariance analysis of the random segments pistons). b, Mirror configuration -Flat. c, Mirror Configuration -mirror segments with random displacements [SI: Video_S1]. d, Histogram of the mirror displacements for 100 mirror configurations in which the displacement range was 1m (0  0.5 m); Abbreviations: L#: Lens, VL: variable focus length liquid lens, ...

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Section: In Vivo Application Of Apm-ao-oct Reduces Speckle Efficientlsupporting

confidence: 91%

Section: Comparison With Similar Methods Of Speckle Reductionmentioning

confidence: 99%

See 1 more Smart Citation

Aperture Phase Modulation with Adaptive Optics: A Novel Approach for Speckle Reduction and Structure Extraction in Optical Coherence Tomography

Zhang

Manna

Miller

et al. 2018

Preprint

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“…The oblique flood illumination enables fast full-field image acquisition that does not depend on biological processes, such as organelle motion [18], [15]. The light radiant exposure at the imaged area of the retina that is comparable with existing technologies.…”

Section: Discussionmentioning

confidence: 99%

Transscleral optical phase imaging of the human retina

et al. 2020

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The in vivo observation of the human retina at the cellular level is crucial to detect lesions before irreversible visual loss occurs, to follow the time course of retinal diseases and to evaluate and monitor the early effects of treatments. Despite the phenomenal advances in optical coherence tomography (OCT) and adaptive optics systems, in vivo imaging of several retinal cells is still elusive. Here we propose a radically different method compared to OCT, called transscleral optical phase imaging (TOPI), which allows to image retinal cells with high contrast, high resolution, and within an acquisition time suitable for clinical use. TOPI relies on high-angle oblique illumination of the retina, combined with adaptive optics, to enhance the phase contrast of transparent cells. We first present in-vivo images of retinal cells, from the retinal pigment epithelium (RPE) to the nerve and vascular layers of the retina, in eleven healthy volunteers without pupil dilation. The morphology of the cells in vivo is then compared to that of images obtained with the same technique applied on ex vivo human RPE and pig retinas. Finally, we demonstrate the ability of high resolution phase microscopy to image pericytes and microglia around rat retinal capillaries. Our results show the ability of TOPI to image and quantify retinal cells up to the RPE depth within a maximum time of 9 seconds over a field of view of 4.4 x 4.4°, opening new avenue in the in vivo exploration of the deepest layer of the retina in healthy and diseased eyes.

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“…Until now, electrical signals in photoreceptors and other retinal cells have been measured using intracellular or extracellular electrodes [1]- [3]. Recently, phase-resolved imaging of photoreceptors demonstrated significant changes in the optical path length (OPL) in response to flash stimuli [4]- [6]. Similarly, nm-scale OPL changes accompanying the action potential have been observed in spiking neurons ex-vivo, and have been shown to faithfully reproduce changes in the cell potential [7]- [9].…”

Section: Introductionmentioning

confidence: 99%

On mechanisms of light-induced deformations in photoreceptors

Boyle

Chen

Ling

et al. 2020

Preprint

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Photoreceptors in the retina convert light into electrical signals through a phototransduction cycle that consists of multiple electrical and biochemical events. Phase-resolved optical coherence tomography (pOCT) measurements of the optical path length (OPL) change in the cone photoreceptor outer segments after a light stimulus (optoretinogram) reveal a fast, ms-scale contraction by tens of nm, followed by a slow (hundreds of ms) elongation reaching hundreds of nm. Ultrafast measurements with a line-scan pOCT system show that the contractile response amplitude increases logarithmically with the number of incident photons, and its peak shifts earlier at higher stimulus intensities.We present a model that accounts for these features of the contractile response. Conformational changes in opsins after photoisomerization result in the fractional shift of charge across the disk membrane, leading to a transmembrane voltage change, known as the early receptor potential (ERP). Lateral repulsion of the ions on both sides of the membrane affects its surface tension and leads to its lateral expansion. Since the volume of the disks does not change much on a ms time scale, their lateral expansion leads to an axial contraction of the outer segment. With increasing stimulus intensity and resulting tension, the area expansion coefficient of the disk membrane also increases as thermally-induced fluctuations are pulled flat, resisting further expansion. This results in a logarithmic saturation of the deformation and a peak shift to earlier with brighter stimuli. Slow expansion of the photoreceptors is explained by the influx of water due to osmotic changes during phototransduction. Both effects closely match measurements in healthy human volunteers.

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Imaging and quantifying ganglion cells and other transparent neurons in the living human retina

Cited by 174 publications

References 48 publications

Aperture Phase Modulation with Adaptive Optics: A Novel Approach for Speckle Reduction and Structure Extraction in Optical Coherence Tomography

Aperture Phase Modulation with Adaptive Optics: A Novel Approach for Speckle Reduction and Structure Extraction in Optical Coherence Tomography

Transscleral optical phase imaging of the human retina

On mechanisms of light-induced deformations in photoreceptors

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