复曲面人工晶状体个体化模型眼成像质量的优化

背景 复曲面人工晶状体(IOL)植入术后术眼的视觉质量受陡峭轴和平坦轴放大率的差异、散光残留及角膜个体球差等因素的影响,通过矫正复曲面IOL的球差是否能有效提高其对患者个体的成像质量是值得研究的问题. 目的 采集患者眼部解剖参数,利用Zemax光学设计软件建立个体化模型眼,研究不同球差的Toric IOL植入后的视觉质量,即不同空间频率的对比敏感度(CSF).方法 采用前瞻性研究设计.连续纳入2012年8月至2013年10月于河北医科大学第二医院眼科拟行白内障超声乳化手术的白内障患者45例45眼,应用Pentacam测量患眼角膜地形图参数,包括角膜前后表面高度、角膜厚度、角膜前表面散光平坦轴和陡峭轴曲率半径、屈光度以及角膜后表面曲率半径,然后应用Matlab 4.5数学计算软件并使用Toric面型公式1描述角膜散光,用非球面状态设置角膜前表面散光模型和角膜后表面模型,根据Holladay Ⅰ公式计算Toric IOL在眼中的有效位置,采用Zemax光学设计软件构建个体化模型眼.根据调制传递函数神经传递函数值分别测定强光环境(300 Td)下瞳孔直径为3 mm以及暗光环境(0.3～1.0Td)下瞳孔直径为5 mm时不同球面Toric IOL在各空间频率的对比敏感度(CSF). 结果 个体化模型眼与受检眼Pentacam测定的角膜散光度分别为(1.51±0.36)D和(1.49±0.37)D,散光轴向分别为(101.5±59.8)°和(101.9±58.5)°,差异均无统计学意义(t=0.886、0.652,均P＞0.05);Bland-Ahman检验显示个体化模型眼与受检眼Pentacam测定的角膜散光度和轴向具有较好的一致性.强光和暗光环境下非球面不同球差Toric IOL模型眼在1.5、3.0、6.0、12.0和18.0 c/d空间频率条件下LogCSF值均高于球面IOL模型眼,非球面球差为-0.13 μm和-0.26 μm Toric IOL模型眼在各空间频率条件下LogCSF值均明显高于0μm球差Toric IOL模型眼,差异均有统计学意义(均P＜O.05).结论 本研究中依据白内障患者眼部解剖参数,利用Zemax光学设计软件成功建立了精确的个体化角膜散光模型,表明非球面Toric IOL能消除角膜球差,提高模型眼的视觉质量.

Optimization of optical performance of biconvex Toric intraocular lens using a customized vision model

Background The optic quality of Toric intraocular lens (IOL)-implanted eye is affected by the residual astigmatism and individual difference of corneal spherical aberration and different magnification from steep and flat axis refraction.Whether correcting Toric IOL spherical aberration can effectively improve the image quality of individual patient is a question to be studied.Objective This study attempted to collect eye parameters of cataract patients to reconstruct the customized vision model by using Zemax optical software,and to evaluate the image performance with different Toric IOL spherical aberration.Methods A prospective study was performed.Forty-five eyes of 45 cataract patients were included in Second Hospital of Hebei Medical University from August 2012 to October 2013.Several relevant parameters were measured by Pentacam,including anterior and posterior surface height of cornea,corneal thickness,curvature radius of flat and steep meridians of anterior surface astigmatism,refractive diopter and curvature radius of posterior surface.The astigmatism of anterior and posterior corneal surface was described by Matlab 4.5 software.Corneal astigmatism model were set as aspheric state,and the effective position of Toric IOL was calculated using Holladay Ⅰ formula.Customized individual model eyes were constructed by Zemax software.The contrast sensitivity function (CSF) of different spherical Toric IOLs at different spatial frequencies were calculated and compared between 300 Td light environment with 3 mm pupil diameter (photopia light) and 0.3-1.0 Td light environment with 5 mm pupil diameter (mesopia light).This study was approved by Second Hospital of Hebei Medical University ethics committee,all the patients signed the informed consent.Results The mean astigmatism power was (1.51 ± 0.36) D and (1.49 ± 0.37) D,and the mean astigmatism meridian was (101.5 ± 59.8) ° and (101.9±58.5) ° in the model eyes and cataract eyes,respectively,without significant differences between them (t=0.886,0.652;both at P＞0.05).Bland-Altman test showed a good agreement in astigmatism power and astigmatism meridian between model eyes and cataract eyes.The LogCSF values at 1.5,3.0,6.0,12.0 and 18.0 c/d spatial frequencies were significantly higher in the aspherical Toric IOL model eyes than those in the spherical Toric IOL model eyes,and the LogCSF values at various spatial frequencies were significantly higher in the Toric IOLs with spherical aberrations of-0.13 μm and-0.26 μm than those in the zero spherical aberrations in both photopia light and mesopia light (all at P＜0.05).Conclusions A precise corneal astigmatism model based on cornea high data of cataract eyes was successfully constructed through special formulas with Zemax software.Aspherical Toric IOL can compensate for spherical aberration of cornea and enhance the optic quality in individual model eye.