15 research outputs found
Exploration 4D de la rétine pour la photocoagulation laser assistée par optique adaptative
Retinal laser photocoagulation is commonly used to treat Diabetic Macular Edema. However, it is impossible with current laser systems to prevent some degree of damage to healthy neighboring tissues, due to the lack of control of the 3D confinement and position of the laser impact. These limitations are mostly caused by ocular aberrations and the constant eye movement. Adaptive Optics (AO) is a technology used since 1997 which enables ocular aberrations compensation in real-time, providing images of the retina with an unbeaten resolution. Laser photocoagulation systems could benefit from the AO capacity to control the 3D confinement of the therapeutic laser and to generate high-resolution retinal images that could be used to guide the surgeon and to control the 3D position of the laser impact in the retina. However, a great effort still has to be made to meet laser photocoagulation requirements. This thesis consists of the design and realization of the first 3D high-resolution AO-assisted Laser Photocoagulation system. For this end, we first present a high spatiotemporal resolution characterization of the 3D PSF evolution within the eye, enabling the design of a high-performance AO system, adapted to a therapeutic application, \ie 3D control of the laser confinement. Then, I used the high-resolution retinal imaging system ECURoeil to validate these results and develop new methods enabling the 4D exploration of the retina (volume + temporal evolution) in real-time, for 3D control of the laser impact position. Finally, all the developments have been brought together in the CLOVIS3D bench, a compact instrument to perform clinically the first therapeutic application of Adaptive Optics.La photocoagulation laser rĂ©tinienne est couramment utilisĂ©e pour traiter l'oedĂšme maculaire diabĂ©tique. Cependant, il est impossible avec les systĂšmes laser actuels d'empĂȘcher un certain degrĂ© d'endommagement des tissus sains adjacents, en raison du manque de contrĂŽle du confinement et de la position 3D de l'impact laser sur la rĂ©tine. Ces limitations sont principalement causĂ©es par des aberrations et mouvements oculaires. L'optique adaptative (OA) est une technologie utilisĂ©e depuis 1997 qui permet la compensation des aberrations oculaires en temps rĂ©el, en fournissant des images de la rĂ©tine avec une rĂ©solution Ă la limite de la diffraction. Les systĂšmes de photocoagulation laser pourraient bĂ©nĂ©ficier de la capacitĂ© de l'OA Ă contrĂŽler le confinement 3D du laser thĂ©rapeutique et Ă gĂ©nĂ©rer des images rĂ©tiniennes Ă haute rĂ©solution qui pourraient ĂȘtre utilisĂ©es ensuite pour guider le chirurgien et contrĂŽler la position 3D de l'impact laser dans la rĂ©tine. Cependant, un grand effort doit encore ĂȘtre fait pour rĂ©pondre aux exigences de photocoagulation laser. Cette thĂšse consiste en la conception et la rĂ©alisation du premier systĂšme de photocoagulation laser assistĂ©e par Optique Adaptative. Pour cela, Ă partir de la caractĂ©risation de l'Ă©volution du confinement 3D de l'impact laser dans l'oeil, nous avons pu conclure sur le design d'un systĂšme d'OA pour l'oeil adaptĂ© aux exigences de la thĂ©rapie laser, c'est-Ă -dire le contrĂŽle du confinement 3D de l'impact laser. Ensuite, j'ai exploitĂ© le banc d'imagerie de la rĂ©tine Ă haute performance ECURoeil pour valider ces rĂ©sultats et dĂ©velopper de nouvelles mĂ©thodes permettant l'exploration 4D de la rĂ©tine (volume + Ă©volution temporelle) en temps rĂ©el, pour le contrĂŽle 3D de la position d'impact laser. Enfin, l'ensemble de ces dĂ©veloppements ont Ă©tĂ© rĂ©unis dans le banc CLOVIS3D, un instrument compact visant Ă rĂ©aliser en clinique la premiĂšre application thĂ©rapeutique de l'optique adaptative
Adaptive-glasses time-domain FFOCT for wide-field high-resolution retinal imaging with increased SNR
International audienceThe highest three-dimensional (3D) resolution possible in in vivo retinal imaging is achieved by combining optical coherence tomography (OCT) and adaptive optics. However, this combination brings important limitations, such as small field-of-view and complex, cumbersome systems, preventing so far the translation of this technology from the research lab to clinics. In this Letter, we mitigate these limitations by combining our compact time-domain full-field OCT (FFOCT) with a multi-actuator adaptive lens positioned just in front of the eye, in a technique we call the adaptive-glasses wavefront sensorless approach. Through this approach, we demonstrate that ocular aberrations can be corrected, increasing the FFOCT signal-to-noise ratio (SNR) and enabling imaging of different retinal layers with a 3D cellular resolution over a 5âĂ5â field-of-view, without apparent anisoplanatism
Optical Incoherence Tomography: a method to generate tomographic retinal cross-sections with non-interferometric adaptive optics ophthalmoscopes
International audienceWe present Optical Incoherence Tomography (OIT): a completely digital method to generate tomographic retinal cross-sections from en-face through-focus image stacks acquired by non-interferometric imaging systems, such as en-face adaptive optics (AO)-ophthalmoscopes. We demonstrate that OIT can be applied to different imaging modalities using back-scattered light, including systems without inherent optical sectioning and, for the first time, multiply-scattered light, revealing a distinctive cross-sectional view of the retina. The axial dimension of OIT cross-sections is given in terms of focus position rather than optical path, as in OCT. We explore this property to guide focus position in cases where the user is "blind" focusing, allowing precise plane selection for en-face imaging of retinal pigment epithelium, the vascular plexuses and translucent retinal neurons, such as photoreceptor inner segments and retinal ganglion cells, using respectively autofluorescence, motion contrast and split detection techniques
Tomographie par incohérence optique : une méthode pour générer des coupes tomographiques de la rétine avec des ophtalmoscopes à optique adaptative non interférométrique
International audienceWe present Optical Incoherence Tomography (OIT): a completely digital method to generate tomographic retinal cross-sections from en-face through-focus image stacks acquired by non-interferometric imaging systems, such as en-face adaptive optics (AO)-ophthalmoscopes. We show how to use OIT to guide focus position in cases where the user is âblind" focusing, such as auto fluorescence imaging of the Retinal Pigment Epithelium (RPE). We also demonstrate that OIT can produce distinctive cross-sectional views of the retina using back-scattered, multiply-scattered or even fluorescent light, making it a complementary technique to OCT.Nous prĂ©sentons la Tomographie par IncohĂ©rence Optique (OIT) : une mĂ©thode entiĂšrement numĂ©rique pour gĂ©nĂ©rer des coupes transversales de la rĂ©tine tomographique Ă partir de piles d'images en face acquises pour diffĂ©rents plans focales par des systĂšmes d'imagerie non interfĂ©romĂ©triques, tels que les ophtalmoscopes Ă optique adaptative. Nous montrons comment utiliser l'OIT pour guider la position du plan focal dans les cas oĂč l'utilisateur effectue une mise au point "en aveugle", comme l'imagerie par autofluorescence de l'Ă©pithĂ©lium pigmentaire de la rĂ©tine. Nous dĂ©montrons Ă©galement que l'OIT peut produire des vues en coupe transversale distinctes de la rĂ©tine en utilisant une lumiĂšre rĂ©trodiffusĂ©e, multidiffusĂ©e ou mĂȘme fluorescente, ce qui en fait une technique complĂ©mentaire Ă l'OCT
Coherence gate shaping for wide field high-resolution in vivo retinal imaging with full-field OCT
International audienceAllying high-resolution with a large field-of-view (FOV) is of great importance in the fields of biology and medicine, but it is particularly challenging when imaging non-flat living samples such as the human retina. Indeed, high-resolution is normally achieved with adaptive optics (AO) and scanning methods, which considerably reduce the useful FOV and increase the system complexity. An alternative technique is time-domain full-field optical coherence tomography (FF-OCT), which has already shown its potential for in-vivo high-resolution retinal imaging. Here, we introduce coherence gate shaping for FF-OCT, to optically shape the coherence gate geometry to match the sample curvature, thus achieving a larger FOV than previously possible. Using this instrument, we obtained high-resolution images of living human photoreceptors close to the foveal center without AO and with a 1 mm Ă 1 mm FOV in a single shot. This novel advance enables the extraction of photoreceptor-based biomarkers with ease and spatiotemporal monitoring of individual photoreceptors. We compare our findings with AO-assisted ophthalmoscopes, highlighting the potential of FF-OCT, as a compact system, to become a routine clinical imaging technique
Fixational eye movement: a negligible source of dynamic aberration
International audienceTo evaluate the contribution of fixational eye movements to dynamic aberration, 50 healthy eyes were examined with an original custom-built Shack-Hartmann aberrometer, running at a temporal frequency of 236Hz, with 22 lenslets across a 5mm pupil, synchronized with a 236Hz pupil tracker. A comparison of the dynamic behavior of the first 21 Zernike modes (starting from defocus) with and without digital pupil stabilization, on a 3.4s sequence between blinks, showed that the contribution of fixational eye movements to dynamic aberration is negligible. Therefore we highlighted the fact that a pupil tracker coupled to an Adaptive Optics Ophthalmoscope is not essential to achieve diffraction-limited resolution.Pour Ă©valuer la contribution des mouvements oculaires de fixation Ă l'aberration dynamique, 50 yeux sains ont Ă©tĂ© examinĂ©s avec un aberromĂštre du type Shack-Hartmann, fonctionnant Ă une frĂ©quence temporelle de 236Hz, avec 22 micro-lentilles sur une pupille de 5mm, synchronisĂ©es avec un suiveur pupillaire de 236Hz. Une comparaison du comportement dynamique des 21 premiers modes de Zernike (Ă partir de la dĂ©focalisation) avec et sans stabilisation numĂ©rique de la pupille, sur une sĂ©quence de 3.4s entre les clignements, a montrĂ© que la contribution des mouvements oculaires de fixation Ă l'aberration dynamique est nĂ©gligeable. Par consĂ©quent, nous avons soulignĂ© le fait qu'un suiveur pupillaire couplĂ© Ă un ophtalmoscope assistĂ© par lâOptique Adaptative n'est pas essentiel pour obtenir une rĂ©solution limitĂ©e par la diffraction
Higher adaptive optics loop rate enhances axial resolution in nonconfocal ophthalmoscopes
International audienceIn this Letter, we propose a way to better understand the impact of dynamic ocular aberrations in the axial resolution of nonconfocal adaptive optics (AO) ophthalmoscopes via a simulation of the 3D PSF in the retina for various AO-loop rates. We then use optical incoherence tomography, a method enabling the generation of tomographic retinal cross sections in incoherent imaging systems, to evaluate the benefits of a fast AO-loop rate on axial resolution and, consequently, on AO-corrected retinal image quality. We used the PARIS AO flood-illumination ophthalmoscope for this study, where retinal images from different focal planes at an AO-loop rate of 10 and 50 Hz were acquired