【作者】 李蕊；

【导师】 王肇圻；

【作者基本信息】 南开大学 ， 光学工程， 2012， 博士

【摘要】 由于人眼屈光系统的复杂性，除了存在离焦和像散这样的低阶像差外，还存在各种非规则的高阶像差，它们也是限制视力的重要因素。波前技术的发展，使得验光不再局限于主观验光的离焦和像散，还可以获得包括球差、彗差等高阶像差在内的信息，波前技术使个性化的视觉矫正成为可能。此外，视觉系统包括眼球的光学系统和视网膜之后的神经系统两部分，分段评价整个视觉系统的成像质量，是视觉矫正治疗的前提和目的。神经对比敏感度函数的获取能够为许多眼科疾病的早期发现与及时治疗提供依据。本文以最优化地矫正人眼像差为主要研究方向，应用波前像差技术，基于个性化的眼光学结构，对以框架眼镜和角膜接触镜为视觉矫正手段的设计方法，以及视功能的评价方面进行了如下研究：设计了球-柱型波前眼镜。通过综合考虑人眼的2~6阶波前像差，在光学设计软件ZEMAX中建立起个体眼光学结构，在此基础上设计了波前球-柱型眼镜的结构，并给出矫正方案，经过模拟已有文献方法并与之对比，证明本文方法的屈光度结果可信。这种用眼模型设计镜片的方法，更适宜分析镜-眼系统在不同视场角和眼球有旋转时的成像质量。通过对随机选取的50只人眼进行建模分析，发现其中36只眼用这种球-柱镜进行矫正即能达到良好的视觉效果；14只眼仅球-柱矫正后成像改善不明显，尚需要其它面型的进一步矫正。通过改进Liou的标准眼模型，运用测量的人眼波前像差数据，将离焦引入至晶状体和玻璃体，散光和高阶像差引入至角膜，建立了符合人眼调节特性的个体眼模型。针对于球-柱镜矫正无效的高阶像差较大的个体眼进行屈光矫正设计，利用光学设计中多重结构的设定对应眼球的旋转，每一结构下视场角的设定对应特定的视场要求，从而将人眼的视物特征纳入至镜片的设计中。针对于不同像差特征的人眼，分别将镜片设计为非球面-环曲面型，以及自由曲面-环曲面型。矫正结果表明，对于像散较大、球差较大的眼睛，非球面镜片矫正有效，在大视场的改善尤为明显；对于高阶像差较高，尤其是彗差、三叶草类像差较高的被试眼，自由曲面型眼镜对其矫正最为有效，不仅体现在大视场成像质量的明显提升，甚至对于中心0°视场成像的改善也有成效。这种基于人眼视物特征、运用特殊面型设计镜片的方法，对于某些像散和高阶像差大的人眼的视觉矫正有特殊意义。提出了一种根据眼视光的客观测量数据获得角膜接触镜面型结构的方法。根据实际测量的角膜地形图数据，运用MATLAB软件编程对角膜前表面进行最佳球面或环曲面拟合，从而设计了角膜接触镜的后表面光学区的面型结构。结合实际测量的人眼波前像差数据，根据衍射的角谱理论，计算波前由出瞳平面传播到角膜前表面、经由泪液透镜及在角膜接触镜介质内的传播，得到角膜接触镜前表面的等效波前像差，进而运用最小二乘法拟合得到矫正该波前像差的角膜接触镜前表面光学区的最优的环曲面面型。由已设计完成的角膜接触镜的前后表面光学区的面型结构，计算和拟合得到该角膜接触镜的最优球、柱度和散光轴位角。经过与人眼波前、泪液镜的屈光度进行比较，证明本方法结果的可信。与传统配镜的0.125D精度相比，本章拟合得到的屈光度精度仅为0.04D。为了得到人眼在时间频率下的神经对比敏感度函数，对全眼时间频率下的对比敏感度函数和人眼波前像差分别进行测量。通过建立被试眼的个体眼模型得到眼屈光系统的调制传递函数，再根据对比敏感度函数和调制传递函数间的关联，通过数值计算得到时间频率下的神经对比敏感度函数曲线。测试结果表明：随着时间频率的增高，神经对比敏感度函数曲线整体大幅度降低，并且表现出由类似“带通”至“低通”再过渡至近乎“单调下降”的特点。表征高、低两种时间频率下神经对比敏感度函数变化特征的衰减因子，随空间频率的增加变化平缓，反映了视觉神经系统对于不同运动速度物体的响应特点。更多还原

【Abstract】 The refractive system of eye is complicated, and there exist defocus, astigmatismand high-order aberrations which play a role in human vision. As the development ofthe wave-front technique, optometry is not only able to obtain the information of thedefocus and astigmatism, but also the information of the high-order aberrations, suchas spherical aberration, coma and so on. And correcting high-order aberrations of eyesbecomes possible as the development of the measurement technique of eye’swavefront aberrations. The visual function of human eye can be divided into twocascading processes, one is the refraction of the eye’s optics and the other is theretina–brain neural course. Segmentation evaluation the image quality of the entirevisual system is the precondition and the objective of the vision correction. Neuralcontrast sensitivity function can provide some predictions for lots of eye problems,which is beneficial for timely clinical treatment.This dissertation mainly concentrates on the study on optimized correcting theaberrations of the eyes. Based on the wavefront technology and individual eye model,optical designing method for the correction instruments of spectacle lens and contactlens and the evaluation method for the visual function are both investigated asfollows:The wavefront-guided sphero-cylindrical spectacles are designed. By taking intoaccount the2~6order wavefront aberrations, the individual eye model is constructedin optical design software ZEMAX. On the basis of that, the sphero-cylindricalspectacles are optimized and the prescriptions of the spectacles are provided.Compared with the data resulting from other method, it is justified to be correct.Through setting the individual eye model, this lens design is fit to analyze theimaging quality of the lens-eye system for various viewing fields and rotationalangles of the eye. By modeling in ZEMAX for randomly chosen50eyes, it is foundthat36eyes among them perform well in visual quality with sphero-cylindricalcorrection only and14eyes perform unsatisfactorily with sphero-cylindrical correction and need further correction.With the measured wavefront aberrations data, the Liou eye model is modifiedby means of transferring the defocus into the crystalline lens and the vitreous bodywhile transferring the astigmatism and high-order aberrations into the cornea. Afterthat the individual eye model is set up with the accommodation characteristics in agood agreement with natural eye. Aiming on correcting the high-order aberrations ofvisions which can not be realized by sphero-cylindrical spectacles, the new type ofspectacles is designed. The viewing characteristics are took into consideration bysetting the lens-eye system as multi-configurations, corresponding to the case ofeyeball’s rotations, and by setting certain fields of view for each configuration,corresponding to the case of certain viewing field. The spectacles are respectivelydesigned into the aspheric-toric form and the freeform-toric form for eyes withdifferent features of wavefront aberrations. It is demonstrated that for the eyes withhigher astigmatism and spherical aberration, the aspheric lens is needed to yield amuch better vision correction especially for larger field of view, while for the eyeswith larger high-order aberrations, such as coma and trefoil, the freeform lens caneliminate the influence of these aberrations on the vision and provide goodperformance either for larger field of view or for central filed of view. Due to theviewing characteristics settings and special profiles optimization, this lens design hassignificance in improving the vision for some specific eyes with high astigmatism andhigh-order aberrations.The method to acquire the structure of the contact lens is proposed on the basisof the objectively measured ophthalmological data. With the data of the cornealtopography, the anterior corneal surface is fitted with the optimized sphere or toricprofile and then the optical zone of the back surface of contact lens is determined.With the data of the wavefront aberrations of eye and the diffraction theory of angularspectrum, the equivalent wavefront at the front surface of the contact lens is acquiredby a propagation procedure of the ocular wavefront aberrations through tear film andlens medium, and then the optimized toric profile for the front surface of the lens isobtained with the least square fitting method to correct the wavefront aberrations atthat plane. Finally, the equivalent spherical and cylindrical powers as well as the astigmatism angle of the contact lens are calculated with the structures of the contactlens. By comparison of the ocular refraction power with the corrector refractionpower (contact lens plus tear lens), this method is proved to be correct. Comparedwith the accuracy of clinical vision correction of0.125D by traditional methodnowadays, the maximum difference of the refraction power is0.04D for our method.In order to get the neural contrast sensitivity function (NCSF) at temporalfrequencies of human eyes, the contrast sensitivity function (CSF) at temporalfrequencies and the wavefront aberrations of the eye are respectively measured. Theeye’s modulation transfer function (MTF) is obtained by constructing the individualeye model of the subject and then the NCSF at temporal frequencies is calculated byrelating the MTF with CSF. The results demonstrate that the overall value of theNCSF decreases as the temporal frequency increases while the form of NCSF curvetakes on the band-pass shape to the low-pass shape, and then to almost monotonicvariation. The attenuation factor of the NCSF, which represents the sensitivity ofvisual neural system to the temporal frequency, varies little as spatial frequencyincreases and it reflects the resolution characteristics of visual neural system to themotion object.更多还原