The binocular intraocular lens power difference in eyes with different axial lengths

AIM:To investigate the binocular intraocular lens(IOL)power difference in eyes with short,normal,and long axial lengths(AL)using Lenstar LS 900 optical biometry.METHODS:A total of 716(1432 eyes)participants were included.The groups were categorized into short(group A:AL<22 mm),normal(group B:22 mm≤AL≤25 mm),and long AL groups(group C:AL>25 mm).The central corneal thickness(CCT),anterior chamber depth(ACD),lens thickness(LT),AL,anterior corneal keratometry,whiteto-white(WTW),pupil diameter(PD),as well as IOL power calculated using embedded Barrett formula were assessed.Bland-Altman plots were used to test the agreement of the binocular parameters.RESULTS:In group A,the CCT of the right eye was significantly thinner than that of the left eye(P=0.044)with a difference of-2±8μm[95%limits of agreement(LoA),-17.8 to 13.2μm].For group B,the PD and IOL power in the right eye were significantly lower than those of the left eye(P=0.001,<0.001)with a difference of-0.05±0.32 mm(95%LoA,-0.68 to 0.58 mm)and-0.18±1.01 D(95%LoA,-2.2 to 1.8 D).The AL of right eye was longer than that of the left eye(P=0.002)with a difference of 0.04±0.25 mm(95%Lo A,-0.45 to 0.52 mm).No significant difference was observed for all the binocular parameters in group C.The percentage of participants with binocular IOL power difference within±0.5 D were 62%(31/50),68.3%(339/496),and 38.8%(66/170)in groups A,B,and C,respectively.CONCLUSION:The binocular parameters related to IOL power are in good agreement,but the binocular IOL power difference of more than half of participants with long AL is more than 0.50 D.

Machine learning adaptation of intraocular lens power calculation for a patient group

Background:To examine the effectiveness of the use of machine learning for adapting an intraocular lens(IOL)power calculation for a patient group.Methods:In this retrospective study,the clinical records of 1,611 eyes of 1,169 Japanese patients who received a single model of monofocal IOL(SN60WF,Alcon)at Miyata Eye Hospital were reviewed and analyzed.Using biometric metrics and postoperative refractions of 1211 eyes of 769 patients,constants of the SRK/T and Haigis formulas were optimized.The SRK/T formula was adapted using a support vector regressor.Prediction errors in the use of adapted formulas as well as the SRK/T,Haigis,Hill-RBF and Barrett Universal II formulas were evaluated with data from 395 eyes of 395 distinct patients.Mean prediction errors,median absolute errors,and percentages of eyes within±0.25 D,±0.50 D,and±1.00 D,and over+0.50 D of errors were compared among formulas.Results:The mean prediction errors in the use of the SRT/K and adapted formulas were smaller than the use of other formulas(P<0.001).In the absolute errors,the Hill-RBF and adapted methods were better than others.The performance of the Barrett Universal II was not better than the others for the patient group.There were the least eyes with hyperopic refractive errors(16.5%)in the use of the adapted formula.Conclusions:Adapting IOL power calculations using machine learning technology with data from a particular patient group was effective and promising.

Intraocular lens power calculation in eyes with previous corneal refractive surgery

Background:This review aims to explain the reasons why intraocular lens(IOL)power calculation is challenging in eyes with previous corneal refractive surgery and what solutions are currently available to obtain more accurate results.Review:After IOL implantation in eyes with previous LASIK,PRK or RK,a refractive surprise can occur because (i)the altered ratio between the anterior and posterior corneal surface makes the keratometric index invalid;(ii)the corneal curvature radius is measured out of the optical zone;and (iii)the effective lens position is erroneously predicted if such a prediction is based on the post-refractive surgery corneal curvature.Different methods are currently available to obtain the best refractive outcomes in these eyes,even when the perioperative data(i.e.preoperative corneal power and surgically induced refractive change)are not known.In this review,we describe the most accurate methods based on our clinical studies.Conclusions:IOL power calculation after myopic corneal refractive surgery can be calculated with a variety of methods that lead to relatively accurate outcomes,with 60 to 70%of eyes showing a prediction error within 0.50 diopters.

Error induced by the estimation of the corneal power and the effective lens position with a rotationally asymmetric refractive multifocal intraocular lens

AIM : To evaluate the prediction error in intraocular lens(IOL) power calculation for a rotationally asymmetric refractive multifocal IOL and the impact on this error of the optimization of the keratometric estimation of the corneal power and the prediction of the effective lens position(ELP).METHODS: Retrospective study including a total of 25 eyes of 13 patients(age, 50 to 83y) with previous cataract surgery with implantation of the Lentis Mplus LS-312 IOL(Oculentis Gmb H, Germany). In all cases, an adjusted IOL power(P IOLadj) was calculated based on Gaussian optics using a variable keratometric index value(n kadj) for the estimation of the corneal power(P kadj) and on a new value for ELP(ELP adj) obtained by multiple regression analysis.This P IOLadj was compared with the IOL power implanted(P IOLReal) and the value proposed by three conventional formulas(Haigis, Hoffer Q and Holladay Ⅰ).RESULTS: P IOLReal was not significantly different than P IOLadj and Holladay IOL power(P 】0.05). In the Bland and Altman analysis, P IOLadj showed lower mean difference(-0.07 D) and limits of agreement(of 1.47 and-1.61 D)when compared to P IOLReal than the IOL power value obtained with the Holladay formula. Furthermore, ELP adj was significantly lower than ELP calculated with other conventional formulas(P 【0.01) and was found to be dependent on axial length, anterior chamber depth and P kadj. CONCLUSION: Refractive outcomes after cataract surgery with implantation of the multifocal IOL Lentis Mplus LS-312 can be optimized by minimizing thekeratometric error and by estimating ELP using a mathematical expression dependent on anatomical factors.

Machine learning adaptation of intraocular lens power calculation for a patient group

Background:To examine the effectiveness of the use of machine learning for adapting an intraocular lens(IOL)power calculation for a patient group.Methods:In this retrospective study,the clinical records of 1,611 eyes of 1,169 Japanese patients who received a single model of monofocal IOL(SN60WF,Alcon)at Miyata Eye Hospital were reviewed and analyzed.Using biometric metrics and postoperative refractions of 1211 eyes of 769 patients,constants of the SRK/T and Haigis formulas were optimized.The SRK/T formula was adapted using a support vector regressor.Prediction errors in the use of adapted formulas as well as the SRK/T,Haigis,Hill-RBF and Barrett Universal II formulas were evaluated with data from 395 eyes of 395 distinct patients.Mean prediction errors,median absolute errors,and percentages of eyes within±0.25 D,±0.50 D,and±1.00 D,and over+0.50 D of errors were compared among formulas.Results:The mean prediction errors in the use of the SRT/K and adapted formulas were smaller than the use of other formulas(P<0.001).In the absolute errors,the Hill-RBF and adapted methods were better than others.The performance of the Barrett Universal II was not better than the others for the patient group.There were the least eyes with hyperopic refractive errors(16.5%)in the use of the adapted formula.Conclusions:Adapting IOL power calculations using machine learning technology with data from a particular patient group was effective and promising.

The associations of lens power with age, axial length and type 2 diabetes mellitus in Chinese adults aged 50 years and above

Background:To investigate the associations of lens power with age,axial length(AL),and type 2 diabetes mellitus(DM)inChineseadultsaged5oandabove.Methods:Random clustering sampling was used to identify adults aged 50 years and above in urban regions of Shanghai.The participants underwent a comprehensive ophthalmic examination including subjective refraction,autorefraction,and IOL-Master.The crystalline lens power was calculated using Bennett's formula.Results:A total of 4177 adults were included.A linear decrease in lens power was observed both with age and with AL,followed by a stop of lens power loss after the age of 70 or when AL≥25 mm,respectively.Participants with type 2 DM presented higher lens power(0.43 diopter(D),P<0.001)and thicker lens thickness(0.06 mm,P<0.001).In multivariate regression models,there was a positive correlation between lens power and type 2 DM when age<75 years(P<0.001)or AL<25 mm(P<0.001)after adjusting for other factors,while no significant association was found in participants aged≥75 years(P=0.122)or with AL≥25 mm(P=0.172).Conclusions:The lens power in adults aged 50 and above exhibited two stages with age and with AL.Type 2 DM caused an increase in lens power,which was not seen in participants aged≥75 years or with AL≥25 mm.

The associations of lens power with age,axial length and type 2 diabetes mellitus in Chinese adults aged 50 and above

Background:To investigate the associations of lens power with age,axial length(AL),and Type 2 diabetes mellitus(DM)in Chinese adults aged 50 and above.Methods:Random clustering sampling was used to identify adults aged 50 years and above in urban regions of Shanghai.The participants underwent a comprehensive ophthalmic examination including subjective refraction,autorefraction,and IOL-Master.The crystalline lens power was calculated using Bennett’s formula.Results:A total of 4177 adults were included.A linear decrease in lens power was observed both with age and with AL,followed by a stop of lens power loss after the age of 70 or when AL≥25 mm,respectively.Participants with Type 2 DM presented higher lens power(0.43 diopter(D),p<0.001)and thicker lens thickness(0.06 mm,p<0.001).In multivariate regression models,there was a positive correlation between lens power and Type 2 DM when age<75 years(p<0.001)or AL<25 mm(p<0.001)after adjusting for other factors,while no significant association was found in participants aged≥75 years(p=0.122)or with AL≥25 mm(p=0.172).Conclusions:The lens power in adults aged 50 and above exhibited two stages with age and with AL.Type 2 DM caused an increase in lens power,which was not seen in participants aged≥75 years or with AL≥25 mm.

Objective assessment of the effect of pupil size upon the power distribution of multifocal contact lenses

AIM： To analytically assess the effect of pupil size upon the refractive power distributions of different designs of multifocal contact lenses.METHODS： Two multifocal contact lenses of center-near design and one multifocal contact lens of center-distance design were used in this study. Their power profiles were measured using the NIMO TR1504 device （LAMBDA-X, Belgium）. Based on their power profiles, the power distribution was assessed as a function of pupil size. For the high addition lenses, the resulting refractive power as a function of viewing distance （far, intermediate, and near） and pupil size was also analyzed.RESULTS： The power distribution of the lenses was affected by pupil size differently. One of the lenses showed a significant spread in refractive power distribution, from about ？3 D to 0 D. Generally, the power distribution of the lenses expanded as the pupil diameter became greater. The surface of the lens dedicated for each distance varied substantially with the design of the lens.CONCLUSION： In an experimental basis, our results show how the lenses power distribution is affected by the pupil size and underlined the necessity of careful evaluation of the patient’s visual needs and the optical properties of a multifocal contact lens for achieving the optimal visual outcome.

验光镜片顶焦度量值计量比对与结果分析

本文以2023年内蒙古自治区法定计量检定机构验光镜片的顶焦度量值的计量比对结果为例,对存在的问题进行研究分析,并提出改进建议。

渐进多焦点镜片的设计方法

介绍渐进多焦点镜片的基本原理和设计思想,阐述几种常用的设计方法和各自的优缺点,给出其中一种方法的设计结果,用测试仪检测实际加工的镜片性能。分析结果表明:渐进多焦点镜片可以实现从视远至视近的过渡,视近区的光焦度高于视远区的光焦度,像散可满足使用要求。不同的渐进多焦点镜片设计方法其设计出的光学镜片性能不同,实际设计加工的镜片检测性能与国外软件加工的镜片性能相近。

IOL-Master测量硅油填充眼屈光结果分析

目的评价IOL-Master测量硅油填充眼屈光度数的准确性并分析不同因素与术后屈光误差的关系。方法29例(29眼)硅油填充眼行硅油取出联合人工晶状体(IOL)植入术,术前用IOL-Master进行IOL测量。根据不同病因、硅油放置时间、眼轴、术后并发症等因素进行分类,研究术后视力恢复情况及测量误差产生的原因。结果术后视力较术前均有不同程度的提高,屈光度数的平均预测误差为0.329±0.846(-1.5～-2.0D),眼轴长度(P>0.05)、病因[裂孔源性(t=0.478,P=0.637)、黄斑裂孔(t=0.135,P=0.895)]、是否近视(t=0.435,P=0.667)与术后产生的屈光误差均无相关性,硅油存留时间<1年者术后矫正视力恢复好。结论硅油填充眼患者采用硅油取出联合IOL植入术对视力有一定提高,IOL-Master测量硅油填充眼IOL度数是相对准确、安全、方便的方式。

角膜接触镜专用顶焦度标准器的研制

论述了建立角膜接触镜专用顶焦度标准器的必要性和研制方案所用的原理 ,并给出接触镜专用顶焦度标准器的测试结果和误差分析 。

渐进多焦点镜片面形误差与光焦度关系的分析

渐进多焦点眼镜片能够同时满足视远与视近的需求,其应用日益广泛.本文介绍了渐进多焦点镜片的设计与评价方法,在此基础上通过对镜片面形方程及球面度方程求解偏微分,构建了渐进多焦点镜片光焦度分布与面形误差的关系模型.根据国家标准规定的镜片有效区域实际屈光度与名义值差值小于0.1 D的要求,对加光度为2.0D(6.0D8.0D)的渐进面面形误差进行了实例分析.应用给定的面形误差结果进行实验加工的镜片,经分析后实验输出的光焦度变化符合所设定的国家标准要求的范围,进一步验证了面形误差与光焦度分布关系模型的正确性,为渐进多焦点镜片加工的面形控制精度提供理论依据.

有限湍流尺度对红外大气成像系统分辨率的影响

采用包含大气湍流内、外尺度的调制折射率谱函数分析了湍流尺度对Fried相干参数(大气相干直径)的影响,给出了Fried参数修正关系。结果表明大气湍流的内尺度对Fried相干参数影响不大,然而由于尺度为L0的大气湍流透镜和相干Fried湍涡的相互作用以及它们对传播光波的衍射作用,有限大气湍流外尺度“增大”了Fried大气相干直径。

超声乳化联合负度数人工晶状体植入治疗白内障合并超高度近视

目的观察超声乳化白内障吸除联合负度数人工晶状体植入术治疗白内障合并超高度近视的临床疗效。方法对15例(26眼)白内障合并超高度近视眼患者,施行超声乳化白内障吸除联合负度数人工晶状体植入术,记录术前矫正视力、眼轴长度、屈光度数及其与预期屈光度数的偏差值,观察手术并发症和术后眼部情况。结果术前眼轴长度30.12～35.76mm,平均为32.45mm。术中均顺利植入人工晶状体,无后囊破裂发生。植入屈光度数为-1.0～-6.0D,术后1周,24眼视力均有不同程度的提高,最佳矫正视力≥0.2共20眼(76.9%),其中≥0.5者共8眼(30.77%)。2眼因严重的黄斑区网膜萎缩变性,视力无明显提高。术后屈光度数偏差值<±2.00D共22眼(84.6%),<±1.00D共14眼(53.8%)。随访时间为3～24个月。后囊膜皱褶6眼,后发性白内障7眼,5眼行激光后囊膜切开术,无视网膜和脉络膜脱离发生,无眼压升高。4例单眼白内障患者中,1例出现双眼干扰症状。结论超声乳化白内障吸除联合负度数人工晶状体植入既可以进行屈光矫正,又可以增加眼内组织的稳定性,减少视网膜脱离的发生,是治疗白内障合并超高度近视眼安全、有效的方法。

图像处理在MDT测量镜片屈光度中的应用

从莫尔偏折技术(MDT)测量镜片屈光度的原理出发,给出了镜片屈光度与莫尔条纹倾角的关系式。进行了实验采集,获取了MDT实测镜片屈光度的莫尔条纹图。然后,基于莫尔条纹图像的特点,采用合适的图像处理算法对实测镜片的莫尔条纹图进行了灰度均匀化、降噪、图像增强、细化等一系列的数字图像处理操作,得到了镜片测量中莫尔条纹图形的清晰轮廓线。最后,给出了不同镜片屈光度的MDT测量结果,并与焦度计的测量结果进行了比较。结果表明,莫尔偏折技术结合数字图像处理用于测量镜片的屈光度时,具有很高的测量精度。

医学显微图像自动拼接的方法研究

图像拼接技术能够很好地解决显微镜高倍镜下图像视野减小的问题。本研究针对医学显微图像的特点 ,提出了降低分辨率全图搜索算法 ,并具体讨论了拼接缝处理和图像显示等问题。实验证明 ,采用该算法人工参与少 ,客观性好 ,硬件依赖性小 ,速度快 ,能够得到满意的拼接结果。

内渐进多焦点镜片的加工

介绍了加工内渐进多焦点镜片的自由曲面数控机床的基本结构及工作原理,开展了机床的加工工艺实验,用以改善内渐进多焦点镜片的光学性能。实验结果表明,车削阶段影响表面粗糙度的两个主要因素是镜片材料和切削速度;得到了抛光效果良好的两个抛光参数:抛光时间是50s—100s,抛光气压是0.03 MPa—0.06 MPa;不同材料的镜片车削后表面粗糙度不同,抛光后表面粗糙度基本相同。

哈特曼法检测渐进多焦点镜片

介绍了哈特曼法检测眼镜片的测量原理及对远轴光线的屈光度补偿,采用哈特曼法对渐进多焦点镜片进行检测。提出了实验总体方案并得到CCD采样图,通过后续图像处理,理论上可以得到镜片的屈光度分布图。结果表明,哈特曼法检测渐进多焦点镜片结构简单,方便可行。

莫尔偏折技术用于测量镜片屈光度的研究

本文从莫尔偏折技术的基本原理出发,结合镜片屈光度的概念,分别从泰伯效应与光栅遮光阴影原理相结合以及菲涅耳-基尔霍夫理论的角度推导了变形后的莫尔条纹倾角与被测镜片屈光度的关系。两种方法推算结果是一致的,即:镜片的屈光度与透过镜片后产生的莫尔条纹的倾角的正切成正比。对影响镜片屈光度测量误差的几个参量进行了讨论,理论分析表明,选用合适的光栅周期,设定合理的两光栅间夹角,莫尔偏折技术用于测量低屈光度及中高屈光度的镜片具有很高的测量精度。最后给出了测量单光镜片、非球面镜片和渐进多焦点镜片的莫尔条纹图,并进行了分析讨论。