个性化人眼模型及精准角膜手术研究

发布时间：2018-03-03 22:28

本文选题：人眼模型　切入点：屈光手术　出处：《中国科学院研究生院(上海应用物理研究所)》2017年硕士论文　论文类型：学位论文

【摘要】：人眼是一台精巧而复杂的光学成像系统,将外部世界投射在视网膜上。然而,并非所有的人眼都可以清晰成像,据不完全统计,世界上约20-30%的人群受到眼球屈光不正的影响(包括近视、远视、散光和混合类型等),其中绝大部分是近视,因此近视被列为人类三大疾病之一。近视眼角膜屈光手术是通过激光烧灼靠近角膜前表面的部分角膜基质从而改变其前表面曲率半径,并使得术后眼球整体屈光度与变长了的近视眼轴长相匹配,达到修正视觉的目的。角膜屈光手术已有几十年的历史,在临床上发展出多种类型,治疗效果参差不齐。人眼精密而复杂,但并非理想的光学成像系统,其复合结构存在内禀像差,它的空间极限分辨能力要小于无像差的同口径的小孔所对应的衍射极限。眼球也不是完美对称的球形,各介质的折射率分布不均匀性,介质边界曲面的不规则性或位置异常等因素对视觉质量产生影响,为精确修正眼球的屈光不正带来困难。另外,目前有很多报道称患者在成功接受Lasik手术后存在夜视力明显下降的问题(光晕、炫光等)。因此本次研究针对任意人眼,提出了个性化的精确角膜手术方案,力图解决夜视力下降的问题并且全面提升术后视力及视觉品质。文中首先建立了典型的-2D和-5D(即通常所说的近视眼200度和500度)个性化近视眼模型,并模拟三种不同手术方案(即球面修正、Q值优化和波前像差引导的Lasik手术),然后着重比较了各手术方案前后的视网膜光斑分布图,波前像差图,以及眼球中各阶像差的变化等,从而显示并对比了手术对于视觉修正的效果。此外,散光反映了人眼中折射率分布的不对称性,是人眼中除离焦外最重要的像差之一。角膜屈光手术主要通过改变角膜前表面屈光状态从而矫正近视,并没有考虑散光来源于角膜前表面还是眼内。眼内的散光是否会对手术后的视觉质量造成影响,目前的临床研究报道还很少。所以我们又分别建立两种基于-5D近视的散光模型:眼表散光(即角膜前表面散光)和眼内散光(多指源于晶状体的散光),同样也模拟对比了以上三种不同手术方案及手术前后的视觉质量。研究结果表明:1.传统的球面修正和Q值优化的Lasik手术对角膜前表面引起的散光有抑制作用,然而对眼内散光的矫正效果较差;2.球面修正会引入较大的球差,Q值优化可以减小术后的球差,但两种手术方案都无法修正眼内其他高阶像差;3.波前像差引导的手术对任何类型的近视、散光或是无规则的高阶像差都可以全面的修正,以实现最佳的人眼成像能力,甚至超视力。
[Abstract]:The human eye is a sophisticated and complex optical imaging system that projects the outside world onto the retina. However, not all human eyes can clearly image, according to incomplete statistics, About 20-30 percent of the world's population is affected by refractive errors (including myopia, hyperopia, astigmatism and mixed types), most of which are myopia. Therefore myopia is listed as one of the three major diseases in human beings. Myopia corneal refractive surgery changes the curvature radius of the anterior surface by laser cauterizing part of the corneal stroma near the anterior surface of the cornea. The global refraction of the eyeball is matched with the axial length of the lengthened myopia, and the vision is corrected. Corneal refractive surgery has a history of decades, and has developed many types in clinical practice. The therapeutic effect is uneven. The human eye is precise and complex, but it is not an ideal optical imaging system, and its compound structure has intrinsic aberration. Its spatial limit resolution is smaller than the diffraction limit corresponding to the aperture of the same aperture without aberration. The eyeball is not a perfect symmetric sphere, and the refractive index distribution of each medium is not uniform. The irregularity of the media boundary surface or the abnormal position influence the visual quality, which makes it difficult to correct the ametropia of the eyeball accurately. At present, there are many reports that the patients' visual acuity (halo, glare, etc.) decreased significantly after successful Lasik surgery. Therefore, this study proposed a personalized and accurate corneal surgery for any person. In order to solve the problem of nocturnal vision loss and improve postoperative visual acuity and visual quality, a typical personalized myopia model of -2D and -5D (that is, 200 degrees and 500 degrees of myopia) was established in this paper. Three different surgical schemes (spherical modified Q value optimization and wavefront aberration guided Lasik operation) were simulated, and the distribution of retinal spot, wavefront aberration, and the changes of various order aberrations in the eyeball were compared before and after the operation. In addition, astigmatism reflects the asymmetry of refractive index distribution in human eyes. Corneal refractive surgery corrects myopia mainly by changing the refractive state of the anterior surface of the cornea. Whether astigmatism comes from the anterior surface of the cornea or within the eye does not take into account whether the astigmatism in the eye will affect the visual quality after the operation. At present, there are few reports of clinical studies. So we have established two kinds of astigmatism models based on -5D myopia: surface astigmatism (i.e. corneal anterior surface astigmatism) and intraocular astigmatism (mainly from lens astigmatism). The results show that the traditional spherical correction and Q-optimized Lasik surgery can inhibit the astigmatism caused by the anterior surface of cornea. However, the correction effect of intraocular astigmatism is poor. The spherical correction will introduce a large spherical aberration Q value optimization can reduce the postoperative spherical aberration. But neither of them can correct other higher-order aberrations in the eye. Wavefront aberration guided surgery can be fully corrected for any type of myopia, astigmatism, or irregular high-order aberrations, in order to achieve optimal human imaging capabilities. Even super eyesight.
【学位授予单位】：中国科学院研究生院(上海应用物理研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R779.6;TP391.41

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