基于微机械薄膜变形镜的人眼视网膜成像研究

高分辨率视网膜图像能够为视网膜疾病的早期诊断、治疗、人眼视觉的科学研究提供重要依据。本研究探讨人眼像差和高分辨率视网膜图像的像差补偿技术,着重H-S传感器像差测量、波前重构算法、变形镜控制算法,提出了基于微机械薄膜变形镜的自适应光学系统闭环控制。通过校正模拟眼的静态像差和人眼的动态像差的实验表明,能够达到减小人眼像差、获得人眼视网膜细胞的初步图像,为进一步获取视网膜各层细胞图像提供了理论和实验依据。     

准分子激光人眼像差矫正系统的研究

准分子激光人眼像差矫正系统旨在实现个性化切削,它不仅能进行正常的屈光矫正,而且可以减少高阶的光学像差,能够减少由LASIK手术引起的像差和夜间视物障碍。准分子激光人眼像差矫正系统包括主观式像差仪进行波前像差的测量、准分子激光系统进行像差矫正两大部分。描述了人眼波前像差的概念、成因以及表示的方法,着重研究了Zernike多项式与人眼波前像差的对应关系,利用主观空间分辨屈光计原理制成的主观式像差仪进行人眼波前像差的测量;研究了准分子激光人眼像差矫正系统的原理和系统软件控制框图,对准分子激光切削角膜的机理、飞点扫描技术、主动眼球跟踪技术、激光的能量闭环控制技术等关键技术作了阐述。研究的成果直接用于准分子激光人眼像差矫正系统,已通过动物试验,目前正在进行临床实验。     

自适应光学在眼科屈光手术中的应用

自适应光学理论中的哈特曼-夏克(Hartmann-Shack)波前传感技术是实时测量人眼睛波前像差的有效、可靠和准确的方法.而利用所得到的波前像差数据引导进行的"个体化"角膜屈光手术能明显减少手术后眼睛屈光系统的高阶像差,提高眼睛的成像质量和视觉灵敏度.     

863计划“活体人眼视网膜细胞自适应光学成像仪研制及临床应用”课题已通过验收

在国家863计划、中科院知识创新工程、国家自然科学基金等支持下,中科院成都光电所将自行建立的世界上第一套基于19单元整体集成式微小变形镜的轻小型“活体人眼视网膜自适应光学成像系统”做了改进,研制出基于37单元微小变形镜的“活体人眼视网膜细胞自适应光学成像仪”。经实验应用,可稳定获取更高分辨率的相对于黄斑中心凹不同区域、不同层面的视网膜细胞图像,以及更高分辨率的眼底视网膜毛细血管图像。     

角膜个性化切削系统的新进展

个性化切削(customized ablation)是在PRK、LASIK的基础上发展起来的一种新的屈光手术技术，它不仅可以进行正常的屈光矫正，而且可以减少高阶的光学像差，从而在一定程度上解决了PRK、LASIK手术所不能解决的问题，通过对角膜的个性化切削，使人眼达到“超常视力”(supemormal vision)。在不久的将来有可能取代PRK、LASIK手术。在临床得到广泛应用。个性化切削手术使用的个性化切削手术系统应运而生。本文将对角膜个性化切削系统的新进展情况作一综述。     

大鼠脑缺血不同时期躯体感觉诱发电位的研究

脑电信号（EEG）具有较高的时间分辨率、可观测脑内活动的动态变化、完全无损检测等优点,常用于对神经系统疾病的诊断,本研究探讨脑缺血后躯体感觉诱发电位（SEP）变化及大脑皮层的功能恢复。利用线栓法建模成功的25只SD雄性大鼠分为5组,分别为正常对照组和左侧中动脉缺血术后4、24、 48 h和1周4个实验组。采用SEP记录法,在术后不同时间段电刺激大鼠的右前爪正中神经支配区,记录对照组和实验组左侧皮层脑电信号,提取SEP,并对安静状态下的脑电进行频谱分析,定量评价左侧中动脉缺血后初级体感皮层SEP及功率谱变化过程。实验结果显示,术后4 h,SD大鼠左侧大脑皮层测得的SEP潜伏期较正常状态显著增大（（16.0±1.1）ms vs（33.7±1.3）ms,P<0.01）,波幅变小（（197.2±13.0）μV vs（25.1±2.0）μV,P<0.01）,θ波、α波、β波、γ波的能量明显变小。θ波：（139 367.86±178.66）μV^2vs（2.22±0.40）μV²,P <0.01;α波:（5389.33±25.55）μV² vs（0.23±0.01）μV²,P<0.01;β波：（7911±416）μV² vs（0.01±0.01）μV²,p<0.01; γ波：（0.30±0.12）μV² vs（0.00±0.00）μV²,P<0.01。随着术后时间的延长,上述特征与对照组的差距逐渐缩小,但还不能达到正常状态的水平。研究提示,SEP可在一定程度上反映脑缺血大鼠大脑皮层功能的变化。     

基于衍射理论的色差分析与处理

目的:研究怎样利用波动光学的衍射理论分析处理色差。方法:从基于点源圆孔衍射的成像原理出发,参考有关文献,经过适当的推理得到了单色光经无单色像差系统所成像点的光场分布计算式,分析了位置色差和倍率色差的衍射机理并给出了色差的计算式,探讨了光学系统的色差校正和光电探测图像的色差校正以及色差的可利用性。结果:跟几何光学相比,利用衍射理论对色差的分析与处理,不但更深入地揭示了色差产生的机理,还对光学系统和光电探测图像的色差计算与校正有一定程度的改进。结论:这些基于衍射理论的色差分析与处理的观点及其方法,有利于在光学工程中对色差进行分析与处理,并且能够促进像差理论的进一步发展。     

改良差时贴壁法分离培养鉴定小鼠骨髓间充质干细胞和内皮前体细胞

目的 探索同时从小鼠骨髓分离培养间充质干细胞(MSCs)与内皮前体细胞(EPCs)及对其鉴定的方法。方法 小鼠骨髓细胞经改良差时贴壁法分离,以48h为时间点,48h内贴壁细胞传至3代后行成骨、成软骨、成脂分化诱导实验,流式细胞术（FCM）检测其表面标记;48h后收集未贴壁细胞,传至3代后行血管形成实验,传至5代后行CD31免疫荧光细胞染色实验,FCM检测其表面标记。 结果 第3代48h内贴壁细胞可诱导分化为骨、软骨和脂肪细胞,FCM 检测Sca-1、CD29、CD45、CD11b 阳性率分别为（98.30±0.75）%,（97.47±1.32）%,（1.87±0.15）%,（1.03±0.71）%;第3代48h后贴壁细胞在基质胶上可形成血管样结构,第5代48h后贴壁细胞特异性表面抗原CD31呈阳性表达,FCM检测CD34、CD133、血管内皮生长因子受体（VEGFR2） 阳性率分别为（88.90±1.18）%,（92.73±2.90）%,（87.63±1.79）%。 结论 采用改良差时贴壁法可同时分离培养扩增小鼠骨髓 MSCs和 EPCs,且简便高效稳定可重复。     

自适应光学技术原理及临床应用价值

光学系统具有自动适应外界条件变化,保持良好工作状态的能力的新技术,在临床上校正高阶像差及细胞水平的高分辨率成像上已得到长足的发展与应用。该文介绍了自适应光学技术的原理,临床应用的优势与发展前景。     

多模型血压自适应控制(用硝普钠)

为了适应病人的个体差异及手术过程中病人特性的变化,本文提出了多模型自适应控制(MMAC)的控制方法。其基本设计思想是:假设对象动态特性可由数个模型之一来表示,各模型均有一控制器与之配合,有一基于对象响应与模型响应之差关系工作的自适应机构,决定最能代表对象特性的模型,从而相应地决定了控制器。由于增益和时延对动态特性影响较大,为此各模型的增益互不相同,其他参数均一致,时延开始设为50秒,每当设定值变化≥20mmHg时,时延重新辩识。采用Smith预报器来消除这种延迟的影响。本文还给出了一系列     

Optimization of the open-loop liquid crystal adaptive optics retinal imaging system

An open-loop adaptive optics (AO) system for retinal imaging was constructed using a liquid crystal spatial light modulator (LC-SLM) as the wavefront compensator. Due to the dispersion of the LC-SLM, there was only one illumination source for both aberration detection and retinal imaging in this system. To increase the field of view (FOV) for retinal imaging, a modified mechanical shutter was integrated into the illumination channel to control the size of the illumination spot on the fundus. The AO loop was operated in a pulsing mode, and the fundus was illuminated twice by two laser impulses in a single AO correction loop. As a result, the FOV for retinal imaging was increased to 1.7-deg without compromising the aberration detection accuracy. The correction precision of the open-loop AO system was evaluated in a closed-loop configuration; the residual error is approximately 0.0909λ (root-mean-square, RMS), and the Strehl ratio ranges to 0.7217. Two subjects with differing rates of myopia (-3D and -5D) were tested. High-resolution images of capillaries and photoreceptors were obtained.     

Characteristics of the human isoplanatic patch and implications for adaptive optics retinal imaging

Conventional adaptive optics enables correction of high-order aberrations of the eye, but only for a single retinal point. When imaging extended regions of the retina, aberrations increase away from this point and degrade image quality. The zone over which aberrations do not change significantly is called the "isoplanatic patch." Literature concerning the human isoplanatic patch is incomplete. We determine foveal isoplanatic patch characteristics by performing Hartmann-Shack aberrometry in 1 deg increments in 8 directions on 7 human eyes. Using these measurements, we establish the correction quality required to yield at least 80% of the potential patch size for a given eye. Single-point correction systems (conventional adaptive optics) and multiple-point correction systems (multiconjugate adaptive optics) are simulated. Results are compared to a model eye. Using the Marechal criterion for 555-nm light, average isoplanatic patch diameter for our subjects is 0.80+/-0.10 deg. The required order of aberration correction depends on desired image quality over the patch. For the more realistically achievable criterion of 0.1 mum root mean square (rms) wavefront error over a 6.0-mm pupil, correction to at least sixth order is recommended for all adaptive optics systems. The most important aberrations to target for a multiconjugate correction are defocus, astigmatism, and coma.     

Theoretical modeling and evaluation of the axial resolution of the adaptive optics scanning laser ophthalmoscope

We present axial resolution calculated using a mathematical model of the adaptive optics scanning laser ophthalmoscope (AOSLO). The peak intensity and the width of the axial intensity response are computed with the residual Zernike coefficients after the aberrations are corrected using adaptive optics for eight subjects and compared with the axial resolution of a diffraction-limited eye. The AOSLO currently uses a confocal pinhole that is 80 microm, or 3.48 times the width of the Airy disk radius of the collection optics, and projects to 7.41 microm on the retina. For this pinhole, the axial resolution of a diffraction-limited system is 114 microm and the computed axial resolution varies between 120 and 146 microm for the human subjects included in this study. The results of this analysis indicate that to improve axial resolution, it is best to reduce the pinhole size. The resulting reduction in detected light may demand, however, a more sophisticated adaptive optics system. The study also shows that imaging systems with large pinholes are relatively insensitive to misalignment in the lateral positioning of the confocal pinhole. However, when small pinholes are used to maximize resolution, alignment becomes critical.     

Double peacock eye optical element for extended focal depth imaging with ophthalmic applications

The aged human eye is commonly affected by presbyopia, and therefore, it gradually loses its capability to form images of objects placed at different distances. Extended depth of focus (EDOF) imaging elements can overcome this inability, despite the introduction of a certain amount of aberration. This paper evaluates the EDOF imaging performance of the so-called peacock eye phase diffractive element, which focuses an incident plane wave into a segment of the optical axis and explores the element's potential use for ophthalmic presbyopia compensation optics. Two designs of the element are analyzed: the single peacock eye, which produces one focal segment along the axis, and the double peacock eye, which is a spatially multiplexed element that produces two focal segments with partial overlapping along the axis. The performances of the peacock eye elements are compared with those of multifocal lenses through numerical simulations as well as optical experiments in the image space. The results demonstrate that the peacock eye elements form sharper images along the focal segment than the multifocal lenses and, therefore, are more suitable for presbyopia compensation. The extreme points of the depth of field in the object space, which represent the remote and the near object points, have been experimentally obtained for both the single and the double peacock eye optical elements. The double peacock eye element has better imaging quality for relatively short and intermediate distances than the single peacock eye, whereas the latter seems better for far distance vision.     

Comparison of sorting algorithms to increase the range of Hartmann-Shack aberrometry

Recently many software-based approaches have been suggested for improving the range and accuracy of Hartmann-Shack aberrometry. We compare the performance of four representative algorithms, with a focus on aberrometry for the human eye. Algorithms vary in complexity from the simplistic traditional approach to iterative spline extrapolation based on prior spot measurements. Range is assessed for a variety of aberration types in isolation using computer modeling, and also for complex wavefront shapes using a real adaptive optics system. The effects of common sources of error for ocular wavefront sensing are explored. The results show that the simplest possible iterative algorithm produces comparable range and robustness compared to the more complicated algorithms, while keeping processing time minimal to afford real-time analysis.     

Efficient compensation of Zernike modes and eye aberration patterns using low-cost spatial light modulators

Off-the-shelf spatial light modulators (SLMs) like those commonly included in video projection devices have been seldom used for the compensation of eye aberrations, mainly due to the relatively low dynamic range of the phase retardation that can be introduced at each pixel. They present, however, some interesting features, such as high spatial resolution, easy handling, wide availability, and low cost. We describe an efficient four-level phase encoding scheme that allows us to use conventional SLMs for compensating optical aberrations as those typically found in human eyes. Experimental results are obtained with artificial eyes aberrated by refractive phase plates introducing either single Zernike terms or complex eye aberration patterns. This proof-of-concept is a step toward the use of low-cost, general purpose SLMs for the compensation of eye aberrations.