Contrast-based sensorless adaptive optics for retinal imaging

Conventional adaptive optics ophthalmoscopes use wavefront sensing methods to characterize ocular aberrations for real-time correction. However, there are important situations in which the wavefront sensing step is susceptible to difficulties that affect the accuracy of the correction. To circumvent these, wavefront sensorless adaptive optics (or non-wavefront sensing AO; NS-AO) imaging has recently been developed and has been applied to point-scanning based retinal imaging modalities. In this study we show, for the first time, contrast-based NS-AO ophthalmoscopy for full-frame in vivo imaging of human and animal eyes. We suggest a robust image quality metric that could be used for any imaging modality, and test its performance against other metrics using (physical) model eyes.OCIS codes: (010.1080) Active or adaptive optics, (170.3880) Medical and biological imaging, (170.4460) Ophthalmic optics and devices, (330.4875) Optics of physiological systems     

Imaging translucent cell bodies in the living mouse retina without contrast agents

The transparency of most retinal cell classes typically precludes imaging them in the living eye; unless invasive methods are used that deploy extrinsic contrast agents. Using an adaptive optics scanning light ophthalmoscope (AOSLO) and capitalizing on the large numerical aperture of the mouse eye, we enhanced the contrast from otherwise transparent cells by subtracting the left from the right half of the light distribution in the detector plane. With this approach, it is possible to image the distal processes of photoreceptors, their more proximal cell bodies and the mosaic of horizontal cells in the living mouse retina.OCIS codes: (170.4460) Ophthalmic optics and devices, (330.4300) Vision system - noninvasive assessment, (110.1080) Active or adaptive optics, (330.7324) Visual optics, comparative animal models     

彩色多普勒超声对高度近视眼血流动力学研究

目的:研究高度近视眼血流动力学及其在近视眼病理改变机制中的作用。方法:应用ATL超9型彩色多普勒诊断仪对26例高度近视眼、17例轻中度近视眼及26例正常对照眼的眼动脉(OA)、视网膜中央动脉(CRA)、睫状后动脉(PCA)进行检测。结果:高度近视组、轻中度近视组与正常对照组血流参数比较:OA血流参数无显著性差异(P>0.05)。CRA、PCA的收缩期(PSV)、舒张期(EDV)、平均血流速度(AV)流速均减低, CRA的阻力指数(RI)升高(P<0.05)。轻中度近视组与对照组比较,无显著性差异(P>0.05)。结论:高度近视眼患者CRA、PCA血流速度减低,表明视网膜及睫状血管系统血液灌注不足,可能是引起其病理性眼底改变的因素之一。彩色多普勒超声用于研究眼底血管、高度近视眼血流动力学变化具有临床意义。     

Optical properties of the mouse eye

The Shack-Hartmann wavefront sensor (SHWS) spots upon which ocular aberration measurements depend have poor quality in mice due to light reflected from multiple retinal layers. We have designed and implemented a SHWS that can favor light from a specific retinal layer and measured monochromatic aberrations in 20 eyes from 10 anesthetized C57BL/6J mice. Using this instrument, we show that mice are myopic, not hyperopic as is frequently reported. We have also measured longitudinal chromatic aberration (LCA) of the mouse eye and found that it follows predictions of the water-filled schematic mouse eye. Results indicate that the optical quality of the mouse eye assessed by measurement of its aberrations is remarkably good, better for retinal imaging than the human eye. The dilated mouse eye has a much larger numerical aperture (NA) than that of the dilated human eye (0.5 NA vs. 0.2 NA), but it has a similar amount of root mean square (RMS) higher order aberrations compared to the dilated human eye. These measurements predict that adaptive optics based on this method of wavefront sensing will provide improvements in retinal image quality and potentially two times higher lateral resolution than that in the human eye.     

Influence of sampling window size and orientation on parafoveal cone packing density

We assessed the agreement between sampling windows of different size and orientation on packing density estimates in images of the parafoveal cone mosaic acquired using a flood-illumination adaptive optics retinal camera. Horizontal and vertical oriented sampling windows of different size (320x160 µm, 160x80 µm and 80x40 µm) were selected in two retinal locations along the horizontal meridian in one eye of ten subjects. At each location, cone density tended to decline with decreasing sampling area. Although the differences in cone density estimates were not statistically significant, Bland-Altman plots showed that the agreement between cone density estimated within the different sampling window conditions was moderate. The percentage of the preferred packing arrangements of cones by Voronoi tiles was slightly affected by window size and orientation. The results illustrated the high importance of specifying the size and orientation of the sampling window used to derive cone metric estimates to facilitate comparison of different studies.OCIS codes: (110.1080) Active or adaptive optics, (170.1610) Clinical applications, (110.3925) Metrics     

伴后巩膜葡萄肿的高度近视眼黄斑区视网膜劈裂和脱离的临床研究

目的：运用光学相干断层扫描（OCT）研究伴后巩膜葡萄肿的高度近视患者黄斑区视网膜劈裂和（或）脱离的发生情况。方法：对301例（575眼）经B超确诊伴后巩膜葡萄肿的高度近视患者行完整的眼科检查和OCT检查。结果：伴后巩膜葡萄肿的高度近视的575眼中67眼（53例）发生黄斑区视网膜劈裂和（或）脱离,均有严重的眼底改变,仅5例患者主诉近来视力进展性损伤。结论：伴有后巩膜葡萄肿的高度近视患者的黄斑区视网膜劈裂和（或）脱离通过OCT检查容易检出,对于有严重眼底病变和伴有后巩膜葡萄肿的高度近视患者建议定期行OCT检查。     

Simultaneous measurements of foveal and peripheral aberrations with accommodation in myopic and emmetropic eyes

The difference in peripheral retinal image quality between myopic and emmetropic eyes plays a major role in the design of the optical myopia interventions. Knowing this difference under accommodation can help to understand the limitations of the currently available optical solutions for myopia control. A newly developed dual-angle open-field sensor was used to assess the simultaneous foveal and peripheral ( 20∘ nasal visual field) wavefront aberrations for five target vergences from -0.31 D to -4.0 D in six myopic and five emmetropic participants. With accommodation, the myopic eyes showed myopic shifts, and the emmetropic eyes showed no change in RPR. Furthermore, RPR calculated from simultaneous measurements showed lower intra-subject variability compared to the RPR calculated from peripheral measurements and target vergence. Other aberrations, as well as modulation transfer functions for natural pupils, were similar between the groups and the accommodation levels, foveally and peripherally. Results from viewing the same nearby target with and without spectacles by myopic participants suggest that the accommodative response is not the leading factor controlling the amplitude of accommodation microfluctuations.     

The use of forward scatter to improve retinal vascular imaging with an adaptive optics scanning laser ophthalmoscope

Retinal vascular diseases are a leading cause of blindness and visual disability. The advent of adaptive optics retinal imaging has enabled us to image the retinal vascular at cellular resolutions, but imaging of the vasculature can be difficult due to the complex nature of the images, including features of many other retinal structures, such as the nerve fiber layer, glial and other cells. In this paper we show that varying the size and centration of the confocal aperture of an adaptive optics scanning laser ophthalmoscope (AOSLO) can increase sensitivity to multiply scattered light, especially light forward scattered from the vasculature and erythrocytes. The resulting technique was tested by imaging regions with different retinal tissue reflectivities as well as within the optic nerve head.OCIS codes: (110.1085) Adaptive imaging, (110.1220) Apertures, (170.4460) Ophthalmic optics and devices, (170.1470) Blood or tissue constituent monitoring     

Improved visualization of outer retinal morphology with aberration cancelling reflective optical design for adaptive optics - optical coherence tomography

We present an aberration cancelling optical design for a reflective adaptive optics - optical coherence tomography (AO-OCT) retinal imaging system. The optical performance of this instrument is compared to our previous multimodal AO-OCT/AO-SLO retinal imaging system. The feasibility of new instrumentation for improved visualization of microscopic retinal structures is discussed. Examples of images acquired with this new AO-OCT instrument are presented.OCIS codes: (110.4500) Optical coherence tomography, (010.1080) Active or adaptive optics, (220.1000) Aberration compensation, (170.0110) Imaging systems, (170.4470) Ophthalmology, (120.3890) Medical optics instrumentation     

3D modeling to characterize lamina cribrosa surface and pore geometries using in vivo images from normal and glaucomatous eyes

En face adaptive optics scanning laser ophthalmoscope (AOSLO) images of the anterior lamina cribrosa surface (ALCS) represent a 2D projected view of a 3D laminar surface. Using spectral domain optical coherence tomography images acquired in living monkey eyes, a thin plate spline was used to model the ALCS in 3D. The 2D AOSLO images were registered and projected onto the 3D surface that was then tessellated into a triangular mesh to characterize differences in pore geometry between 2D and 3D images. Following 3D transformation of the anterior laminar surface in 11 normal eyes, mean pore area increased by 5.1 ± 2.0% with a minimal change in pore elongation (mean change = 0.0 ± 0.2%). These small changes were due to the relatively flat laminar surfaces inherent in normal eyes (mean radius of curvature = 3.0 ± 0.5 mm). The mean increase in pore area was larger following 3D transformation in 4 glaucomatous eyes (16.2 ± 6.0%) due to their more steeply curved laminar surfaces (mean radius of curvature = 1.3 ± 0.1 mm), while the change in pore elongation was comparable to that in normal eyes (−0.2 ± 2.0%). This 3D transformation and tessellation method can be used to better characterize and track 3D changes in laminar pore and surface geometries in glaucoma.OCIS codes: (000.3860) Mathematical methods in physics, (110.1080) Active or adaptive optics, (330.4460) Ophthalmic optics and devices     

Adaptive-optics SLO imaging combined with widefield OCT and SLO enables precise 3D localization of fluorescent cells in the mouse retina

Adaptive optics scanning laser ophthalmoscopy (AO-SLO) has recently been used to achieve exquisite subcellular resolution imaging of the mouse retina. Wavefront sensing-based AO typically restricts the field of view to a few degrees of visual angle. As a consequence the relationship between AO-SLO data and larger scale retinal structures and cellular patterns can be difficult to assess. The retinal vasculature affords a large-scale 3D map on which cells and structures can be located during in vivo imaging. Phase-variance OCT (pv-OCT) can efficiently image the vasculature with near-infrared light in a label-free manner, allowing 3D vascular reconstruction with high precision. We combined widefield pv-OCT and SLO imaging with AO-SLO reflection and fluorescence imaging to localize two types of fluorescent cells within the retinal layers: GFP-expressing microglia, the resident macrophages of the retina, and GFP-expressing cone photoreceptor cells. We describe in detail a reflective afocal AO-SLO retinal imaging system designed for high resolution retinal imaging in mice. The optical performance of this instrument is compared to other state-of-the-art AO-based mouse retinal imaging systems. The spatial and temporal resolution of the new AO instrumentation was characterized with angiography of retinal capillaries, including blood-flow velocity analysis. Depth-resolved AO-SLO fluorescent images of microglia and cone photoreceptors are visualized in parallel with 469 nm and 663 nm reflectance images of the microvasculature and other structures. Additional applications of the new instrumentation are discussed.OCIS codes: (170.4460) Ophthalmic optics and devices, (110.4500) Optical coherence tomography, (110.1080) Active or adaptive optics, (170.0110) Imaging systems, (330.7324) Visual optics, comparative animal models, (170.4470) Ophthalmology     

Adaptive optics optical coherence tomography at 1 MHz

Image acquisition speed of optical coherence tomography (OCT) remains a fundamental barrier that limits its scientific and clinical utility. Here we demonstrate a novel multi-camera adaptive optics (AO-)OCT system for ophthalmologic use that operates at 1 million A-lines/s at a wavelength of 790 nm with 5.3 μm axial resolution in retinal tissue. Central to the spectral-domain design is a novel detection channel based on four high-speed spectrometers that receive light sequentially from a 1 × 4 optical switch assembly. Absence of moving parts enables ultra-fast (50ns) and precise switching with low insertion loss (−0.18 dB per channel). This manner of control makes use of all available light in the detection channel and avoids camera dead-time, both critical for imaging at high speeds. Additional benefit in signal-to-noise accrues from the larger numerical aperture afforded by the use of AO and yields retinal images of comparable dynamic range to that of clinical OCT. We validated system performance by a series of experiments that included imaging in both model and human eyes. We demonstrated the performance of our MHz AO-OCT system to capture detailed images of individual retinal nerve fiber bundles and cone photoreceptors. This is the fastest ophthalmic OCT system we know of in the 700 to 915 nm spectral band.OCIS codes: (110.1080) Active or adaptive optics, (170.4500) Optical coherence tomography, (120.3890) Medical optics instrumentation, (170.0110) Imaging systems, (170.4470) Ophthalmology, (330.5310) Vision - photoreceptors     

Understanding the changes of cone reflectance in adaptive optics flood illumination retinal images over three years

Although there is increasing interest in the investigation of cone reflectance variability, little is understood about its characteristics over long time scales. Cone detection and its automation is now becoming a fundamental step in the assessment and monitoring of the health of the retina and in the understanding of the photoreceptor physiology. In this work we provide an insight into the cone reflectance variability over time scales ranging from minutes to three years on the same eye, and for large areas of the retina (≥ 2.0 × 2.0 degrees) at two different retinal eccentricities using a commercial adaptive optics (AO) flood illumination retinal camera. We observed that the difference in reflectance observed in the cones increases with the time separation between the data acquisitions and this may have a negative impact on algorithms attempting to track cones over time. In addition, we determined that displacements of the light source within 0.35 mm of the pupil center, which is the farthest location from the pupil center used by operators of the AO camera to acquire high-quality images of the cone mosaic in clinical studies, does not significantly affect the cone detection and density estimation.OCIS codes: (110.1080) Active or adaptive optics, (330.7331) Visual optics, receptor optics, (170.3880) Medical and biological imaging     

Impact on stereo-acuity of two presbyopia correction approaches: monovision and small aperture inlay

Some of the different currently applied approaches that correct presbyopia may reduce stereovision. In this work, stereo-acuity was measured for two methods: (1) monovision and (2) small aperture inlay in one eye. When performing the experiment, a prototype of a binocular adaptive optics vision analyzer was employed. The system allowed simultaneous measurement and manipulation of the optics in both eyes of a subject. The apparatus incorporated two programmable spatial light modulators: one phase-only device using liquid crystal on silicon technology for wavefront manipulation and one intensity modulator for controlling the exit pupils. The prototype was also equipped with a stimulus generator for creating retinal disparity based on two micro-displays. The three-needle test was programmed for characterizing stereo-acuity. Subjects underwent a two-alternative forced-choice test. The following cases were tested for the stimulus placed at distance: (a) natural vision; (b) 1.5 D monovision; (c) 0.75 D monovision; (d) natural vision and small pupil; (e) 0.75 D monovision and small pupil. In all cases the standard pupil diameter was 4 mm and the small pupil diameter was 1.6 mm. The use of a small aperture significantly reduced the negative impact of monovision on stereopsis. The results of the experiment suggest that combining micro-monovision with a small aperture, which is currently being implemented as a corneal inlay, can yield values of stereoacuity close to those attained under normal binocular vision.OCIS codes: (010.1080) Active or adaptive optics, (330.1400) Vision - binocular and stereopsis     

Wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice

We present wavefront sensorless adaptive optics (WSAO) Fourier domain optical coherence tomography (FD-OCT) for in vivo small animal retinal imaging. WSAO is attractive especially for mouse retinal imaging because it simplifies optical design and eliminates the need for wavefront sensing, which is difficult in the small animal eye. GPU accelerated processing of the OCT data permitted real-time extraction of image quality metrics (intensity) for arbitrarily selected retinal layers to be optimized. Modal control of a commercially available segmented deformable mirror (IrisAO Inc.) provided rapid convergence using a sequential search algorithm. Image quality improvements with WSAO OCT are presented for both pigmented and albino mouse retinal data, acquired in vivo.OCIS codes: (170.4460) Ophthalmic optics and devices, (110.1080) Active or adaptive optics, (110.4500) Optical coherence tomography     

抗VEGF药物对湿性老年性黄斑变性视网膜微循环的疗效研究

目的 研究抗血管内皮生长因子(VEGF)药物对湿性老年性黄斑变性(wAMD)视网膜微循环的临床疗效;方法 回顾性分析2018年6月～2020年7月在同济大学附属杨浦医院收治的wAMD患者38例38眼,包括康柏西普治疗组(A组)及雷珠单抗治疗组(B组),每组各19例。收集两组患者治疗前和治疗后1个月最佳矫正视力,黄斑中心凹以及距离黄斑中心凹0.5 mm四个方位的视网膜厚度,视网膜毛细血管密度,以及黄斑中心凹无灌注区面积的差异;结果 与治疗前相比,两组治疗后视网膜厚度均明显降低(P<0.001),黄斑中心凹无灌注区面积均明显减少(P<0.05);两组治疗后视网膜浅层和深层血管密度均显著增加(P<0.05)。两组治疗后的结果相比较,视网膜微循环相关指标均无显著差异(P>0.05)。结论 玻璃体腔注射康柏西普或者雷珠单抗治疗湿性老年性黄斑变性患者可有效改善黄斑部形态以及视网膜微循环。     

Adaptive optics with pupil tracking for high resolution retinal imaging

Adaptive optics, when integrated into retinal imaging systems, compensates for rapidly changing ocular aberrations in real time and results in improved high resolution images that reveal the photoreceptor mosaic. Imaging the retina at high resolution has numerous potential medical applications, and yet for the development of commercial products that can be used in the clinic, the complexity and high cost of the present research systems have to be addressed. We present a new method to control the deformable mirror in real time based on pupil tracking measurements which uses the default camera for the alignment of the eye in the retinal imaging system and requires no extra cost or hardware. We also present the first experiments done with a compact adaptive optics flood illumination fundus camera where it was possible to compensate for the higher order aberrations of a moving model eye and in vivo in real time based on pupil tracking measurements, without the real time contribution of a wavefront sensor. As an outcome of this research, we showed that pupil tracking can be effectively used as a low cost and practical adaptive optics tool for high resolution retinal imaging because eye movements constitute an important part of the ocular wavefront dynamics.OCIS codes: (110.1080) Active or adaptive optics, (100.4999) Pattern recognition, target tracking, (170.4460) Ophthalmic optics and devices, (170.3890) Medical optics instrumentation     

Wavefront sensorless adaptive optics fluorescence biomicroscope for in vivo retinal imaging in mice

Cellular-resolution in vivo fluorescence imaging is a valuable tool for longitudinal studies of retinal function in vision research. Wavefront sensorless adaptive optics (WSAO) is a developing technology that enables high-resolution imaging of the mouse retina. In place of the conventional method of using a Shack-Hartmann wavefront sensor to measure the aberrations directly, WSAO uses an image quality metric and a search algorithm to drive the shape of the adaptive element (i.e. deformable mirror). WSAO is a robust approach to AO and it is compatible with a compact, low-cost lens-based system. In this report, we demonstrated a hill-climbing algorithm for WSAO with a variable focus lens and deformable mirror for non-invasive in vivo imaging of EGFP (enhanced green fluorescent protein) labelled ganglion cells and microglia cells in the mouse retina.OCIS codes: (170.4460) Ophthalmic optics and devices, (010.1080) Active or adaptive optics, (170.0110) Imaging systems, (170.4470) Ophthalmology     

玻璃体腔注气(C3F8)联合巩膜外引流视网膜下液治疗高度近视黄斑裂孔性视网膜脱离

目的观察玻璃体腔注气（C3F8）联合巩膜外引流视网膜下液治疗高度近视黄斑裂孔性视网膜脱离的疗效。方法采用玻璃体腔注气（C3F8）联合巩膜外引流视网膜下液治疗高度近视黄斑裂孔性视网膜脱离患者32例32眼,观察术后视网膜复位、术后视力及并发症发生情况。结果32例32眼中26例26眼（81．25％）治愈;2例2眼（6．25％）好转;4例4眼（12．5％）朱愈。在治愈的26例26眼中,视力提高21例21眼（80．77％）,视力不变者5例5眼（19．23％）,其中2例发生高眼压,通过降眼压处理恢复正常,未发生其他并发症。结论玻璃体腔注气（C3F8）联合巩膜外引流视网膜下液治疗高度近视黄斑裂孔性视网膜脱离,具有安全、有效、操作简单等特点,叮作为高度近视黄斑裂孔性视网膜脱离患者的首选治疗方法。     

Framework for quantitative three-dimensional choroidal vasculature analysis using optical coherence tomography

Choroidal vasculature plays an important role in the pathogenesis of retinal diseases, such as myopic maculopathy, age-related macular degeneration, diabetic retinopathy, central serous chorioretinopathy, and ocular inflammatory diseases. Current optical coherence tomography (OCT) technology provides three-dimensional visualization of the choroidal angioarchitecture; however, quantitative measures remain challenging. Here, we propose and validate a framework to segment and quantify the choroidal vasculature from a prototype swept-source OCT (PLEX Elite 9000, Carl Zeiss Meditec, USA) using a 3×3 mm scan protocol centered on the macula. Enface images referenced from the retinal pigment epithelium were reconstructed from the volumetric data. The boundaries of the choroidal volume were automatically identified by tracking the choroidal vessel feature structure over the depth, and a selective sliding window was applied for segmenting the vessels adaptively from attenuation-corrected enface images. We achieved a segmentation accuracy of 96% ± 1% as compared with manual annotation, and a dice coefficient of 0.83 ± 0.04 for repeatability. Using this framework on both control (0.00 D to −2.00 D) and highly myopic (−8.00 D to −11.00 D) eyes, we report a decrease in choroidal vessel volume (p<0.001) in eyes with high myopia.