IOE OpenIR  > 光电技术研究所博硕士论文
基于自适应光学的视觉诱发电位测量系统
其他题名
杨彦荣1,2
学位类型博士
导师戴云 ; 杨亚良
2018-05-11
学位授予单位中国科学院大学
学位授予地点北京
学位专业光学工程
关键词视觉诱发电位 自适应光学技术 人眼像差 幅度 潜伏期
摘要

视觉感知的形成离不开屈光系统、视网膜和完整的视觉通路,任何部位的病变或障碍都会造成视觉功能损失,给人们的日常生活带来极大不便。而对于视觉通路异常的诊断常用视功能评估的方法,主要分为主观和客观两类检查。其中基于心理物理学的主观法易受受检者主观判断或认知能力的影响,检查结果变异大,无法适用于一些特殊场合。

而视觉诱发电位测量技术是一种客观的视功能检查方法,特别适合于婴幼儿、智力障碍者、无语言能力的患者,以及癔病、诈盲者等,已成为眼科临床检查的重要手段之一。众所周知,视觉诱发电位测量过程中,刺激图形向视网膜的投射不可避免的受到人眼屈光不正或像差的影响。而传统视觉诱发电位测量时只能以佩戴验光镜片等方式矫正屈光不正。

但是,人眼除屈光不正外,还存在着许多形状更加复杂的高阶像差,它们同样也是影响视网膜像质或视觉性能进一步提升的光学成分,从而也会对视觉诱发电位的测量产生影响。而对于衍射受限下或像差调控下视觉诱发电位的研究至今还未见报道。

本论文正是在这样的背景下,研制基于自适应光学技术的视觉诱发电位测量系统,并在此系统上初步研究了人眼像差对视觉诱发电位的影响。其主要内容概括如下。

首先,仿真分析了视觉诱发电位的测量和提取过程。通过建立提取视觉诱发电位的数学模型,并用同步信号标记刺激图形翻转时刻,分析得出随着同步信号偏差的增大,特征波形的幅度逐渐下降,潜伏期逐渐延长,严重影响了测量的准确性。则为了准确测量视觉诱发电位,必须严格保证同步信号的精度,从而为视觉诱发电位测量系统的研制提供指导。

接着,仿真分析了人眼像差对视网膜像质的影响,提出基于均方根误差和相关系数的数值方法来直观和量化地评价视网膜像质。通过这种评价可直观地了解视觉诱发电位测量时,人眼像差对刺激图形向视网膜投射过程的影响。

再者,研制基于自适应光学技术的视觉诱发电位测量系统,并在小型化、集成化的基础上将瞳孔定位和主动跟踪的技术应用于该系统,降低对被试者配合程度的要求和人为干预,进一步提升系统性能。系统中视觉刺激经图形处理器后由微型OLED(organic light-emitting diode)呈现,同时图形处理器输出一同步信号来精确标记刺激图形的翻转时刻。微型OLED经自适应光学系统投射于视网膜处,从而基于自适应光学技术可以获得高阶像差校正前后或不同校正策略下的刺激图像。通过对比这些情况下的视觉诱发电位特征波形,可以分析研究眼像差对视觉诱发电位的影响,从而为准确地测量视觉诱发电位提供技术和平台,进一步提升其临床价值。

最后,通过比较15°和2°视场下的视觉诱发电位特征波形,验证了2°视场下亦能记录到有效可靠的波形,进而基于自适应光学视觉诱发电位测量系统研究了45位被试者在像差调控下视觉诱发电位的变化情况,继而获得高阶像差校正前后和不同校正策略下的视觉诱发电位波形。则通过自适应光学技术提高视网膜像质后能增强视觉诱发电位特征波形的幅度,但同时不会对潜伏期造成明显影响。从而基于自适应光学技术将视网膜像质或主观视觉感受与视觉诱发电位相联系,为视觉诱发电位的准确测量和应用提供技术和平台支持。

其他摘要

The formation of visual perception was governed by optics, retina and visual pathway. Any visual pathology or disorders at different levels can cause loss of visual function and bring great inconvenience to people's daily life. For diagnosis of visual pathway disorders, the methods of visual function assessment are mainly divided into two types: subjective and objective. The subjective test based on psychophysiological method is easy to be influenced by the subjective judgement or cognitive ability of the subject. As a result, the test cannot be applied to some special occasions.

The technique of visual evoked potential (VEP) measurement is a kind of objective visual function examination method, especially suitable for infants, mentally disabled, no-verbal patients, hysteria, and malingering. VEP has become one of important means of clinical ophthalmology examination. It is well known that, during the VEP measurement, the projection of a stimulus onto the retina is inevitably affected by the refractive errors or ocular aberrations. However, low-order aberrations (LOAs) of the errors can only be corrected by wearing trial lenses in a traditional VEP.

However, in addition to LOAs, there are many higher-order aberrations (HOAs) with more complex shapes. They are also the optical components that influence the further improvement of retinal image quality or visual performance, which would also affect the VEP measurements. However, no relevant studies of using AO to bypass the optical limits in VEP measurement have been reported up to now.

Based on this background, this paper develops a VEP measurement system based on adaptive optics (AO) technology, and preliminarily studies the influence of ocular aberrations on the VEP measurements. The main contents are summarized as follows.

First, the process of measurement and extraction of VEP was simulated and analyzed. By establishing a mathematical model for extracting VEP, we used the synchronized signals to mark the turning time of stimulus pattern. It was found that the synchronization signal bias would decrese the amplitudes and prolong the latencies of VEP waveform gradually. As a result, the accuracy of measurement was seriously affected. In order to obtain the accurate VPE measurement, the accuracy of the synchronous signal must be strictly guaranteed. In this way, the simulation would provide guidance for the development of VEP measurement system.

Also, the influence of ocular aberration on the retinal image quality was simulated and analyzed. A numerical method based on the root mean square error (RMSE) and correlation coefficient (CC) was proposed to directly and quantitatively evaluate the retinal image quality. Through this evaluation, the effect of ocular aberration on the process of stimulus pattern projection onto the retina during the VEP measurements could be directly reflected.

Furthermore, the VEP measurement system based on an AO technology was designed and developed. In order to further improve the performance of this system and reduce the requirements of subject cooperation and manual intervention, the system size was minimized and integrated with a subsystem of pupil position and active eye tracking. In the system, the stimulus pattern was displayed by an OLED (organic light-emitting diode) displayer after a stimulus processor. Meanwhile, the processor output a synchronous signal to accurately mark the time of the stimulus presentation. The stimulus pattern on the OLED was finally projected onto the retina through the AO system. As a result, the VEP measurements could be performed without and wtih HOA correction or under different correction strategies. Compared the characteristic waveforms of VEP between these different strategies, the influence of ocular aberrations on VEP would become clear. The system will provide a platform for the accurate VEP measurements and further improve its clinical value.

Finally, through comparing the VEP waveform between the field sizes of 15° and 2°, it was verified that the effective and reliable VEP waveforms could also be recorded with 2°. Thus, we used the developed system to study the effects of aberration on VEP through the AO aberration regulation technique. The result shown that the VPE characteristic amplitudes were increased with statistical significance (p < 0.05) when using AO to improve the retinal image quality, but it did not have a significant effect on the latencies. Therefore, based on an AO technology, we can connect the retinal image quality or subjective visual perception together with VEP to accurate measurement of the VEP. It would provide the necessary technical and equipment support for future researches on visual function.

学科领域物理学
语种中文
文献类型学位论文
条目标识符http://ir.ioe.ac.cn/handle/181551/8314
专题光电技术研究所博硕士论文
作者单位1.中国科学院光电技术研究所
2.中国科学院大学
推荐引用方式
GB/T 7714
杨彦荣. 基于自适应光学的视觉诱发电位测量系统[D]. 北京. 中国科学院大学,2018.
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