Optoretinography is coming of age.
Optoretinography is coming of age.
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视网膜检光术正在成熟。
DOI：
10.1073/pnas.2119737118
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发表时间：
2021
影响因子：
11.1
通讯作者：
Roorda,Austin
中科院分区：
文献类型：
--
作者：
Roorda,Austin
今天的神经学家可以用来研究大脑和视网膜中神经元的功能和结构的工具令人印象深刻。指示功能活动的荧光探针正在变得更快和更灵敏(1)，正在开发的用于观察它们的成像系统也是如此(2)。电极阵列在三维方向上正变得越来越平行(3)，组合光电记录也成为可能(4)。但是，尽管这些技术令人兴奋，但它们用于人类的翻译仍然存在问题，因为它们的侵入性和潜在毒性产生了伦理和监管障碍。活体人类对具有类似灵敏度和分辨率的细胞级记录的需求不断增加，这推动了视网膜在一种名为视网膜术或ORG的新兴领域的发明和创新。ORG最初由穆利根等人发明(5)，泛指由视网膜神经功能引起的光信号的记录。具有不同名称和实现的组织测量已经进行了几十年(6-11)。眼科手术检查研究的一个主要目标一直是提高检测和测量因疾病导致的功能丧失的能力，因此Lassoued等人。S(12)在《美国国家科学院院刊》上的演示表明，眼病会导致眼科手术检查程序的改变，这代表着该方法的成熟。达到这一点需要几个主要发展的结合。主要的障碍之一是眼睛的自然光学，它已经很好地进化成了视觉，但质量不足以使视网膜的显微图像成为可能。这些障碍在1997年被克服，当时罗切斯特大学的大卫·威廉姆斯领导的一个研究小组--其中还包括Lassoued等人研究的高级作者DT Miller(12)--使用自适应光学(AO)来测量和纠正眼睛的像差，并记录了活体人类的视网膜图像，其中含有分解的视锥感光细胞(13)。从那时起，声光技术不断成熟，以至于近乎衍射限制的光学分辨率现在已经成为常规(14)。另一项重大发展是光学相干层析成像(OCT)，它利用光的干涉特性进行深度分辨测量(15)。这项技术非常适合成像弱散射的视网膜组织，大部分是透明的，并允许对人类视网膜进行横断面和三维成像(图1)。它在临床眼睛护理中的使用现在很常见(16)。光学光学层析成像技术与光学相干断层扫描技术的结合，使视网膜细胞的三维分辨成为可能。直到最近，OCT的轴向深度分辨率主要是通过干涉信号的幅度来获得的，这已经提供了超过一个数量级的轴向分辨率，这比共焦光学在人眼中所能提供的要好(17)。最近，相分辨OCT进一步推动了轴向分辨率的巨大飞跃，提供了对纳米级神经元物理变化的敏感性。Lassoued等人报告的ORG测量的基本前提是：当像光感受器这样的神经元被激发时，细胞中发生的物理变化会延长或缩短其散射面之间的光程长度。在相位分解的OCT中，这些路径长度的变化足够大，足以表现为从眼睛返回的光波的相位的可测量的变化。该相位对组织中的运动非常敏感；对于相对明亮的结构，如光感受器，可以检测到小于10 nm的位移，远远小于系统的轴向分辨率或成像光的波长。什么是…
The arsenal of tools available to today’s neuroscientists to study the function and structure of neurons in the brain and retina is impressive. Fluorescent probes that indicate functional activity are becoming faster and more sensitive (1), as are the imaging systems that are being developed to observe them (2). Electrode arrays are becoming increasingly parallelized in three dimensions (3), and combined optoelectrical recording is also possible (4). But as exciting as these technologies are, their translation for human use remains problematic because of ethical and regulatory barriers arising from their invasiveness and potential toxicity. The increased demand for cellular-level recording with comparable sensitivity and resolution noninvasively in live humans has driven invention and innovation for the retina in an emerging area called optoretinography, or ORG. Originally coined by Mulligan et al.(5), ORG generally refers to the recording of optical signals caused by retinal neuronal function. ORG measurements with various names and realizations have been conducted for decades (6–11). A primary goal of ORG research has been to improve the ability to detect and measure loss of function due to disease, and thus Lassoued et al.’s (12) demonstration in PNAS that eye disease causes a change in the ORG represents the method’s coming of age. It took a combination of several major developments to reach this point. One of the major barriers was the eye’s natural optics, which have evolved nicely for vision, but are not of sufficient quality to enable microscopic images of the retina. These barriers were overcome in 1997 when a team led by David Williams at the University of Rochester—which also included DT Miller, the senior author of the study by Lassoued et al.(12)—used adaptive optics (AO) to measure and correct for aberrations in the eye and recorded retinal images with resolved cone photoreceptor cells in a live human (13). Since that time, AO technology has continued to mature, to the point where near-diffraction-limited optical resolution is now routine (14). Another major development was optical coherence tomography (OCT), which leverages the interference properties of light to make depth-resolved measurements (15). This technology was perfectly suited for imaging the weakly scattering, mostly transparent, tissue of the retina and allowed cross-sectional and three-dimensional imaging of the human retina (Fig. 1). Its use in clinical eye care is now commonplace (16). The integration of AO into OCT made it possible to resolve retinal cells in three dimensions. Until recently, the axial depth resolution of OCT was primarily obtained through the amplitude of the interference signal only, which already offered axial resolutions that were over an order of magnitude better than confocal optics could ever provide in a human eye (17). More recently, phase-resolved OCT has pushed axial resolution a giant leap further, offering sensitivities to physical changes in neurons on a nanometer scale. The basic premise of the ORG measurement as reported by Lassoued et al.(12) is this: When a neuron like a photoreceptor is excited, physical changes in the cell take place that lengthen or shorten the optical path length between its scattering surfaces. In phaseresolved OCT, these path length changes are big enough to manifest as measurable changes in the phase of the light waves returned from the eye. The phase is very sensitive to movement in the tissue; for relatively bright structures such as the photoreceptors, displacements smaller than 10 nm are detectable, much smaller than the axial resolution of the system or the wavelength of the imaging light. What are …