两种基于Scheimpflug成像原理的生物测量仪对眼前节参数测量的一致性研究

目的:评估两种基于Scheimpflug成像技术原理的国产Scansys和进口Sirius三维眼前节分析系统,对近视患者眼前节生物参数测量的差异性与一致性。方法:系列病例研究,选取2022-05/10沈阳爱尔卓越眼科医院诊断为轻中度近视拟行屈光手术(包括全飞秒、半飞秒、TransPRK、ICL植入术)患者103例103眼(所有患者均右眼入组)。收集患者术前角膜曲率(Km)、中央角膜厚度(CCT)、前房深度(ACD Endo.)、前房角(ACA)、前房容积(ACV)、白到白(WTW)。结果:Scansys和Sirius测量术前Km为42.88(41.54,44.60)、42.98(41.56,44.52)D,CCT为541.52±29.08、549.55±29.62μm,ACA为42.70°±2.67°、46.63°±5.13°,WTW为12.10±0.60、11.98±0.47mm,差异均有统计学意义(均P<0.01)。Scansys和Sirius测量ACV为194.26±31.06、191.47±25.65mm 3,ACD Endo.为3.40(3.17,3.57)、3.43(3.19,3.56)mm,差异均无统计学意义(均P>0.05)。两种仪器测量Km、CCT、ACA、ACD Endo.、ACV、WTW值区间范围小,平均差异接近0,95%LoA线外点比例均<5%,一致性较好。结论:Scansys和Sirius对眼前节参数测量结果差异较小,一致性较好,临床上可以相互参考替代。Scansys理论上可以用来推算ICL型号,或可成为眼前节参数测量的一种新选择。

Scheimpflug Imaging of the Anterior Eye Segment during Standardized Accommodation Stimulation in Patients with Emmetropia, Myopia and Hypermetropia

Understanding of the biomechanics of the accommodative apparatus in the eyes with different refraction is important for solving the problems of theoretical and practical ophthalmology. Purpose: To determine the changes of anterior eye segment dimensions during accommodation response in normal eyes and in patients with myopia, hypermetropia. Methods and Material: 116 eyes (56 patients aged from 18 to 30 years, refraction from -2.0 to + 2.0 D) were examined. All the patients underwent a full ophthalmological examination. The ocular anterior segment was imaged using a rotational Scheimpflug camera Pentacam HR (Oculus, Wetzlar, Germany) under non- and 3.0 D of accommodative demands. The statistical data were represented as the mean value ± standard deviation (M ± SD). The Shapiro-Wilk test was used to assess the normality distribution. Wilcoxon test was used for comparison. Results: Results showed an increase in the optical density of the crystalline lens, a pupil diameter decrease and changing of the iris profile during accommodation in all patients. An increase in the total corneal aberrations and decrease in the corneal spherical aberration were revealed only in emmetropic eyes. Conclusions: The accommodative response is a multicomponent process. Scheimpflug visualization revealed the differences in the accommodative response in normal and ametropic eyes.

Pentacam Scheimpflug系统测定晶状体密度及其与超声乳化能量消耗的关系△

目的分析Pentacam Scheimpflug系统测定晶状体密度及其与超声乳化能量消耗的关系。方法回顾性分析2008年7月至2009年1月我院收治的老年性白内障或高度近视并发白内障患者123例(137眼),均行超声乳化白内障吸出及人工晶状体植入术。术前对所有患眼采用Emergy-Little核硬度分级标准进行晶状体分级,并利用PentacamScheimpflug系统测量患眼晶状体密度,采用曲线估计回归分析获得晶状体密度与Emergy-Little核分级、平均超声能量、超声乳化时间和有效超声时间的最佳拟合线,以了解晶状体密度与超声能量消耗的关系。结果通过分析最佳拟合线和确定系数(R2)发现,晶状体密度与Emergy-Little分级呈线性关系(R2=0.78),晶状体密度与平均超声能量(R2=0.51)、超声乳化时间(R2=0.88)和有效超声时间(R2=0.81)均呈指数关系。结论晶状体密度作为一个客观、定量的参数可以用来评估术前白内障程度。在白内障超声乳化中,超声能量的消耗随着晶状体密度的增高呈指数性增加。

应用旋转Scheimpflug照相系统对角膜参数的研究

目的以旋转Scheimpflug照相技术(Pentacam)研究角膜前表面曲率(Ra)、后表面曲率(Rp)及角膜厚度;根据测量结果,探讨角膜屈光力的计算方法。方法应用Pentacam对302名正常角膜的Ra、Rp、角膜厚度及测量所得K值(Km)进行测量,计算Rp与Ra比值(Rp/Ra)、角膜前表面屈光力(Ka)、后表面屈光力(Kp),以几何光学公式计算角膜屈光力(KO)与标定的角膜系数(Nc),对角膜各参数进行正态分布检验,直线回归分析Rp与Ra的相关性。结果各参数均服从正态分布。Ra为(7.74±0.26)mm,Ka为(48.62±1.61)D,CT为(0.545±0.036)mm,与既往报道的数据相似;角膜后表面参数与既往报道的数据及Gullstrand模型眼不同,Rp为(6.44±0.25)mm,Kp为(-6.22±0.24)D,Rp/Ra为0.832±0.017,低于Gullstrand模型眼的参数;Rp与Ra呈直线相关,回归方程为Rp=0.81×Ra+0.17(R2=0.71,P<0.05);Nc为1.3288±0.0010,低于标准的角膜系数1.3375。KO为(42.52±1.42)D,低于Km(43.64±1.44)D,差异有统计学意义(t=151.87,P<0.01)。K1.3288为(42.52±1.41)D,与KO比较差异无统计学意义(t=-0.052,P=0.96)。KO与K1.3288呈直线相关,回归方程为KO=1.006×K1.3288-0.241(R2=0.99,P<0.05)。结论旋转Scheimpflug照相技术与传统角膜地形图仪原理不同,应用该技术发现Rp、Kp、Rp/Ra及Nc与Gullstrand模型眼参数不同,对于标准化角膜光学模型及角膜屈光力的计算具有指导意义。

基于Scheimpflug定律的线结构光系统摄像机标定方法

建立了基于倾斜镜头的摄像机标定模型,给出了利用HALCON软件的简便标定方法。以线结构光传感器模型为基础,深入研究了满足Scheimpflug定律的恒聚焦光路系统,Scheimpflug定律使光敏元件和镜头之间产生了一个夹角,镜头相对于相机是倾斜放置的。针对倾斜镜头的标定做了相应的研究,利用传统摄像机标定的线性与非线性模型建立了基于倾斜镜头的摄像机数学模型,并利用HALCON机器视觉软件给出流程化的标定步骤。

Corvis ST新参数应力-应变指数的研究进展

可视化角膜生物力学分析仪(Corvis ST)是目前评估在体角膜生物力学最常用的临床设备。新参数应力-应变指数(SSI)是近年来临床研究的热点,其不仅可以直接反映角膜生物材料刚度,而且与某些疾病的进展密切相关。SSI是基于使用有限元(FE)数值建模模拟眼内压和Corvis ST喷气效果的角膜行为预测生成的。SSI算法不随着本身中央角膜厚度(CCT)、眼内压以及生物力学矫正眼压(BIOP)的变化而变化,但明显与角巩膜中的胶原纤维改变有关。本文将从SSI的原理、年龄与SSI的关系、眼轴与SSI的关系、近视程度与SSI的关系、SSI的应用等方面进行归纳和总结。

人和动物眼前段的Scheimpflug照相及计算机图像分析

目的 应用Ｓｃｈｅｉｍｐｆｌｕｇ 照相技术在活体内对人眼和几种动物眼的眼前部图像进行测量分析。 方法 应用眼前部图像分析系统（ＥＡＳ１０００ ，日本Ｎｉｄｅｋ） ，对正常成人以及豚鼠、大鼠、兔和猫的眼前部照相并作图像分析。 结果 用ＥＡＳ１０００ 系统能在人眼、豚鼠和大鼠眼得到清晰的眼前部图像，而在兔和猫眼仅得到前半部晶状体以前的图像。测量并比较分析了各种眼球的角膜及晶状体的多个生理参数。 结论 Ｓｃｈｅｉｍｐｆｌｕｇ 照相能获得清晰的眼前段图像。

低中度近视青少年配戴角膜塑形镜1月内角膜生物力学参数检测

目的观察低中度近视青少年配戴角膜塑形镜(orthokeratology,OK镜)1 d、1周及1月时点角膜生物力学的变化。方法纳入初次验配OK镜的低中度近视青少年79例124眼,按等效球镜度(SE)分为低屈光度组(SE为-0.75~3.00 D)40例57眼和中屈光度组(SE为-3.00~-6.00 D)39例67眼,于戴镜前及戴镜1 d、1周及1月时,应用可视化角膜生物力学分析仪(Corvis ST)测量角膜生物力学相关参数【第一次压平时间(A1T)、第一次压平长度(A1L)、第一次压平速率(A1V),峰值距离(PD)、最大形变幅度(HCDA)、最大压陷时曲率半径(HCR)、最大压陷时间(HCT),第二次压平时间(A2T)、第二次压平长度(A2L)、第二次压平速率(A2V),中央角膜厚度(CCT)及眼压(IOP)】。结果戴镜1 d时,低屈光度组IOP较戴镜前降低(P<0.05);戴镜1周与戴镜前及戴镜1 d时比较,低、中屈光度组A1T均缩短(P<0.05),PD、HCDA、A2T均增长(P<0.05),IOP均降低(P<0.05);低屈光度组较戴镜1 d时A1V增快、CCT变薄(P<0.05);中屈光度组CCT较戴镜前及戴镜1 d时均变薄(P<0.05),且ΔPD、ΔA2T小于低屈光度组(P<0.05),ΔCCT大于低屈光度组(P<0.05);戴镜1月时,两组A1T、PD、HCDA、A2T较戴镜前分别缩短、增大、增加、延长(P<0.05),A2V、IOP较戴镜1周时分别减慢、升高(P<0.05),CCT较戴镜1周时趋于稳定;低屈光度组HCR较戴镜1 d时减小(P<0.05),中屈光度组A1V较戴镜1周时减慢(P<0.05)。结论戴OK镜1周时,角膜生物力学特性变化最大,戴镜1月时各项指标趋于稳定,且中屈光度组变化更小、稳定更快。

角膜屈光手术对角膜生物力学影响的研究进展

角膜屈光手术是目前屈光手术的主流术式,随着全飞秒、全激光手术方式的发展,手术变得更加安全精准,不仅角膜创伤小,术后恢复时间也进一步缩短。角膜具有屈光特性和典型的生物软组织力学特性,角膜力学特性不仅参与维持角膜形态,影响角膜手术尤其屈光手术的效果及预后,而且还与部分角膜疾病的发生和发展密切相关。近年来生物力学研究发展迅速,其在眼部疾病的诊疗中发挥着越来越重要的作用。角膜生物力学的变化与术前角膜的形态、不同手术方式的选择、术后角膜厚度的改变等多种因素相关,但手术导致的角膜自身形态改变是不可逆的,若术后角膜生物力学的变化较大,可能会引起医源性角膜扩张、继发性圆锥角膜等并发症的发生。为了规避术后角膜扩张风险和指导个性化的术式选择,了解角膜生物力学特性的影响至关重要。文章对角膜的基础结构、角膜生物力学特性、生物力学测量方法和不同术式及不同角膜瓣厚度术后生物力学变化的研究进展进行综述,为近视患者的个性化精准治疗提供理论指导。

基于Scheimpflug条件实现三维立体重建的研究

本文基于Scheimpflug条件并结合Matlab数学软件,研究了如何实现三维立体重建的实际问题。根据Scheimpflug条件设计光路,利用一束激光照射到被测物体表面,激光在被测物体表面发生反射,然后利用光学透镜对反射光线进行汇聚,成像于光电检测器件线阵CCD。通过CCD成像光斑与被测物体间位置关系可在极短时间内获得复杂工作表面的完整点云,进而获得被测物体表面光斑的位置信息,并采集被测物体表面到参考位置的距离数据,最后通过Matlab软件进行数据拟合处理并实现三维立体重建。

Corneal biomechanical data and biometric parameters measured with Scheimpflug-based devices on normal corneas

AIM： To analyze the correlations between ocular biomechanical and biometric data of the eye,measured by Scheimpflug-based devices on healthy subjects.METHODS： Three consecutive measurements were carried out using the corneal visualization Scheimpflug technology（Cor Vis ST） device on healthy eyes and the 10 device-specific parameters were recorded.Pentacam HR-derived parameters（corneal curvature radii on the anterior and posterior surfaces;apical pachymetry;corneal volume;corneal aberration data;depth,volume and angle of the anterior chamber） and axial length（AL） from IOLMaster were correlated with the 10 specific CorV is ST parameters.RESULTS： Measurements were conducted in 43 eyes of 43 volunteers（age 61.24±15.72y）.The 10 specific Cor Vis ST data showed significant relationships with corneal curvature radii both on the anterior and posterior surface,pachymetric data,root mean square（RMS） data of lower-order aberrations,and posterior RMS of higher-order aberrations and spherical aberration of the posterior cornea.Anterior chamber depth showed a significant relationship,but there were no significant correlations between corneal volume,anterior chamber volume,mean chamber angle or AL and the 10 specific CorV is ST parameters.CONCLUSION： Cor Vis ST-generated parameters are influenced by corneal curvature radii,some corneal RMS data,but corneal volume,anterior chamber volume,chamber angle and AL have no correlation with the biomechan-ical parameters.The parameters measured by CorV is ST seem to refer mostly to corneal properties of the eye.

Evaluation of anterior and posterior surfaces of the cornea using a dual Scheimpflug analyzer in keratoconus patients implanted with intrastromal corneal ring segments

AIM：To evaluate corneal parameters measured with a dual Scheimpflug analyzer in keratoconus patients implanted with intrastromal corneal ring segments（ICRS）.METHODS：Fifty eyes of 40 keratoconus patients had Ferrara ICRS implantation from November 2010 to April2014.Uncorrected visual acuity（UCVA）,best corrected visual acuity（BCVA）,refraction,keratometry,asphericity,elevation,pachymetry,root mean square（RMS）,spherical aberration and coma were studied.All patients were evaluated using a dual Scheimpflug system.RESULTS：The mean follow-up time after the procedure was 12.7mo.The mean UCVA improved from0.82 to 0.31（P〈0.001）;the mean BCVA improved from0.42 to 0.05（P〈0.0001）,the mean spherical refraction changed from-3.06 ±3.80 D to-0.80 ±2.5 D（P〈0.0001）and the mean refraction astigmatism reduced from-4.51 ±2.08 D to-2.26±1.18 D（P〈0.0001）.The changes from preoperative to postoperative,in parameters of the anterior and posterior surface of the cornea,were statistically significant except the elevation posterior at the apex of the cornea and posterior asphericity.CONCLUSION：The implantation of Ferrara ICRS induces changes in both anterior and posterior surfaces of the cornea.

非Scheimpflug条件对激光三角测距精度影响

在激光三角测距方法中,测量系统结构需满足Scheimpflug条件,使得激光光斑与探测器探测成像之间满足物像关系,保证距离测量精度。然而,光学镜头与探测器非共轴的设计结构较为复杂,成本更高,使用不方便。在实际应用中采用成像镜头与相机同轴化直接集成的方式,构建非Scheimpflug条件下的激光三角测距系统,虽然提升了稳定性、方便性,降低了成本,但是不可避免地降低了激光三角测距精度。基于以上背景,开展了非Scheimpflug条件对激光三角测距精度影响研究,建立非Scheimpflug条件下距离测量解析模型,分析激光光斑成像后理论中心位置与质心位置之间的定位误差,并依据距离测量模型解算非Scheimpflug条件下距离测量误差,定量评估非Scheimpflug条件下不同激光三角测距模型的测量精度,给出非Scheimpflug条件下保持测距精度所适用的系统参数和距离范围,为非Scheimpflug条件下激光三角测距法应用提供理论和数值基础。

Comparison of corneal measurements in keratoconic eyes using rotating Scheimpflug camera and scanning-slit topography

AIM: To compare the anterior segment measurements obtained by rotating Scheimpflug camera(Pentacam) and Scanning-slit topography(Orbscan IIz) in keratoconic eyes.METHODS: A total of 121 patients, 71 males(58.7%)and 50 females(41.3%)(214 eyes) with the diagnosis of keratoconus(KC) were enrolled in this study. Following diagnosis of KC by slit-lamp biomicroscopic examination, central corneal thickness(CCT), thinnest corneal thickness(TCT), anterior chamber depth(ACD),and pupil diameter(PD) were measured by a single examiner using successive instrumentation by Pentacam and Orbscan.RESULTS: There was no significant difference between the two instruments for the measurement of CCT and TCT. In contrast, scanning-slit topography measured ACD(3.46±0.40 mm vs 3.38±0.33 mm, P =0.019) and PD(4.97 ±1.26 mm vs 4.08 ±1.19 mm, P 【0.001) significantly larger than rotating Scheimpflug camera.The two devices made similar measurements for CCT(95% CI:-2.94 to5.06, P =0.602). However, the mean difference for TCT was-6.28(95% CI:-10.51 to-2.06, P =0.004) showing a thinner measurement by Orbscan than by Pentacam. In terms of the ACD, the mean difference was 0.08 mm(95%CI: 0.04 to 0.12, P 【0.001) with Orbscan giving a slightly larger value than Pentacam. Similarly, Orbscan measurement for PD was longer than Pentacam(95% CI:0.68 to 1.08, P 【0.001).CONCLUSION: A good agreement was found between Pentacam and Orbscan concerning CCT measurement while comparing scanning-slit topography and rotatingScheimpflug camera there was an underestimation for TCT and overestimation for ACD and PD.

Placido disk-based topography versus high-resolution rotating Scheimpflug camera for corneal power measurements in keratoconic and post-LASIK eyes：reliability and agreement

AIM：To compare the repeatability/reproducibility of measurement by high-resolution Placido disk-based topography with that of a high-resolution rotating Scheimpflug camera and assess the agreement between the two instruments in measuring corneal power in eyes with keratoconus and post-laser in situ keratomileusis（LASIK）. METHODS：One eye each of 36 keratoconic patients and 20 subjects who had undergone LASIK was included in this prospective observational study. Two independent examiners worked in a random order to take three measurements of each eye with both instruments. Four parameters were measured on the anterior cornea：steep keratometry（Ks）,flat keratometry（Kf）,mean keratometry（Km）,and astigmatism（Ks-Kf）. Intra-examiner repeatability and inter-examiner reproducibility were evaluated by calculating the within-subject standard deviation（Sw）the coefficient of repeatability（R）,the coefficient of variation（Co V）,and the intraclass correlation coefficient（ICC）. Agreement between instruments was tested with the BlandAltman method by calculating the 95% limits of agreement（95% Lo A）.RESULTS：In keratoconic eyes,the intra-examiner and inter-examiner ICC were 〉0.95. As compared with measurement by high-resolution Placido disk-based topography,the intra-examiner R of the high-resolution rotating Scheimpflug camera was lower for Kf（0.32 vs 0.88）,Ks（0.61 vs 0.88）,and Km（0.32 vs 0.84）but higher for Ks-Kf（0.70 vs 0.57）. Inter-examiner R values were lower for all parameters measured using the high-resolution rotating Scheimpflug camera. The 95% Lo A were-1.28 to ＋0.55 for Kf,-1.36 to ＋0.99 for Ks,-1.08 to ＋0.50 for Km,and-1.11 to ＋1.48 for Ks-Kf. In the post-LASIK eyes,the intra-examiner andinter-examiner ICC were 〉0.87 for all parameters. The intra-examiner and inter-examiner R were lower for all parameters measured using the high-resolution rotating Scheimpflug camera. The intra-examiner R was 0.17 vs 0.88 for Kf,0.21 vs 0.88 for Ks,0.17 vs 0.86 for Km,and 0.28 vs 0.33 for Ks-Kf. The inter-examiner R was 0.09 vs 0.64 for Kf,0.15 vs 0.56 for Ks,0.09 vs 0.59 for Km,and 0.18 vs 0.23 for Ks-Kf. The 95% Lo A were-0.54 to ＋0.58 for Kf,-0.51 to ＋0.53 for Ks and Km,and-0.28 to ＋0.27 for Ks-Kf. CONCLUSION：As compared with Placido disk-based topography,the high-resolution rotating Scheimpflug camera provides more repeatable and reproducible measurements of Ks,Kf and Ks in keratoconic and post-LASIK eyes. Agreement between instruments is fair in keratoconus and very good in post-LASIK eyes.

Pentacam Scheimpflug成像测量晶状体密度与torsional超声乳化参数间的关系（英文）

目的：评价运用Pentacam Scheimpflug成像测量晶状体核密度与torsinal超声乳化动力学参数（如：运用于老年核性白内障患者的超声能量水平、液体留存时间及液体量）间的关系。方法：此研究为前瞻性双盲研究。瞳孔扩大后运用Pentacam Scheimpflug 成像进行测量。白内障的等级由pentacam核密度测定法[ pentacam nucleus densitometry, PND；又名Pentacam核分段（ Pentacam nucleus staging, PNS）软件]自主分为1到5个等级。超声乳化术后,自动在Infiniti Ozil IP超声乳化系统监视器上计算并显示总超声（ U/S）时间、累计耗散能、Torsional U/S时间以及估算液体的使用情况。组间差异运用单因素方差分析（ ANOVA ）进行评定,多组分析运用Tamhane测试法,PND测量的晶状体密度与torsinal超声乳化动力学参数间的关系运用Spearman相关分析进行评定。界定P〈0.05时具有统计学意义。结果：此项研究包括125例患者（125眼）,平均年龄为69.7±9.4岁（范围：48~88岁）,其中61例男性、64例女性。 U/S总时间、torsional U/S时间、CDE及估算液体使用情况的范围分别为0.70~158.9s,0.70~158.5s,0.11~42.65和21~98mL. PND组间数据有统计学差异。评估超声乳化动力学参数与PND数据间关系后得出PND数据与总超声时间（ r=0.767； P〈0.01）、torsional超声时间（r=0.767；P〈0.01）、CDE（r=0.758； P〈0.01）及液体使用量（r=0.602；P〈0.01）均有显著相关性。结论：白内障手术前运用PND评分法获得核密度的客观程度可为超声乳化术中的参数提供可靠的预见性。因此,对每一位患者进行每一单项超声乳化参数的评估,有助于降低超声乳化能量的使用量,减少内皮细胞丢失和类固醇的使用,加速视力的恢复。

Monitoring of central corneal thickness after phacoemulsification—comparison of statical and rotating Scheimpflug pachymetry,and spectral-domain OCT

AIM:To explore the possibility of deploying three contactless devices(static and rotating Scheimpflug technology,spectral domain optical coherence tomography)for measuring central corneal thickness(CCT)in preoperative and postoperative examinations of cataract patients.METHODS:Totally 72 patients who had undergone surgery without complications were selected.The CCT was measured prior to the operation,as well as on the first,5th-7th and 28th day following the operation using the Nidek NT 530-P,Sirius?,and Topcon OCT-2000 devices.RESULTS:A significant postoperative increase and subsequent decrease in CCT was identified with all three devices.The correlations were highly significant and thus reflect a very good degree of comparability at all times with the exception of the rotating Scheimpflug camera.The postoperative results from the latter differed significantly from the other devices.The correlations were Sirius/Topcon(P=0.010)and Sirius/Nidek(P<0.0005).No statistically significant difference could be identified in the comparison between Topcon and Nidek(P=0.056).CONCLUSION:All three devices are suitable for postoperative monitoring of CCT.The measurement results are only comparable to a limited extent and not interchangeable in the course of treating a single patient.This is due to the different imaging technology used in the devices and the resulting modalities for conducting the measurements.

Measurement of central corneal thickness and precorneal tear film thickness of rabbits using the Scheimpflug system

AIMTo measure central corneal thickness (CCT) and pre-corneal tear film thickness using the Galilei dual-Scheimpflug analyzer (GSA) in New Zealand white rabbits.

Effect of 2% fluorescein on Scheimpflug central corneal thickness measurements

AIM： To assess central corneal thickness （CCT） changes measured with Scheimpflug device following instillation of 2% fluorescein in normal subjects. ~ METHODS： This was a prospective randomized study of 60 hospital volunteers. After baseline CCT measurements of both eyes of 40 subjects were obtained using Scheimpflug system, a drop of preservative-free 2% fluorescein, was instilled in one eye and in other eye, one drop of normal saline （control）. Measurements were repeated after 1, 2, 5, 10, 20, 30, 40, 50 and 60min （continuous assessment group）. Twenty subjects had baseline CCT taken, then fluorescein was instilled in one eye and measurements were taken at lmin. Ten eyes had saline rinse after lmin and 10 other eyes did not, measurements were repeated at 2min （eye rinse group）. RESULTS： The mean baseline CCT for continuous assessment group was 546.2±32.1um （range, 489.0-606.0）, control eyes was 546.6~±30.7 um （range, 489.0-602.0）. At lmin after fluorescein instillation, CCT significantly increased by 37.0±34.0um （P〈0.001）, then decreased gradually, reaching baseline at 60min. CCT variations were not significant in control group （P〉0.05）. For eye rinse group, CCT mean differences between baseline and 2min were 18.2um （95 % Ch -54.7 to 18.3） with rinse and 26.5um （95% CI： -62.9 to 9.9） without rinse; paired sample tests were not significant （P〉0.05）. CONCLUSION： The presence of fluorescein increased CCT value to a clinically relevant level of 6.8%. Eye rinse did not significantly reduce the effect at 2min post fluorescein timepoint.

Fourier analysis of corneal Scheimpflug imaging:clinical use in keratoconus

AIM:To evaluate the clinical use of Fourier analysis of videokeratography data in the diagnosis and follow-up of keratoconus(KC).METHODS:We conducted a chart review of consecutive patients presented to our cornea clinic.A team of two experienced cornea specialists divided the patients into three groups:normal cornea,forme fruste KC(FFKC),and clinical KC.The exclusion criteria were a history of previous ocular surgery,any accompanying corneal pathology other than KC,high myopia(>6.00 diopters),amblyopia,pregnancy,breastfeeding,or any current autoimmune disease.The data of Fourier series harmonic analysis were evaluated for their diagnostic capacity using the receiver operating characteristic(ROC)curve.A binary logistic regression analysis was also conducted to construct a diagnostic model.A total of 259 eyes showed progression in the clinical KC group and underwent a combination of accelerated corneal collagen cross-linking and topographyguided customized treatment with an excimer laser.RESULTS:The study included 1262 eyes(618 normal,530 KC,and 114 FFKC)of 1262 patients.We observed that maximum decentration(MaxDec)was almost as good as maximum keratometry(Kmax)in detecting progressive KC.The area under the curve(AUC)was 0.95 for KC[95%confidence interval(CI):0.93-0.96]and 0.84 for FFKC(95%CI:0.79-0.88).Higher predictive accuracy was obtained using a model combining the spherical component,MaxDec,irregularity,and regular astigmatism in the center of the cornea(AUC:0.97;sensitivity:89%,and specificity:96%).CONCLUSION:Decentration,Kmax,and posterior radii of curvatures from a 3.0-mm optical zone centered on the thinnest point of the cornea provide the highest accuracy with low reproducibility of Kmax.