Resonant behaviors of ultra-sonic gas atomization nozzle with zero mass-flux jet actuator

The resonant behaviors of an ultra-sonic gas atomization nozzle with a zero mass-flux jet actuator were numerically investigated with FLUENT software by using a double precision unsteady two-dimensional pressure-based solver. The Spalart-Allmaras turbulence model was adopted in the simulations. Numerical results indicated that the oscillation properties of the gas efflux were effectively improved. Several resonatory frequencies corresponding to different vibration modes of gas were distinguished in the nozzle. With the changing of nozzle geometric parameters, different characters among those modes were elucidated by analyzing the propagations of pressure waves.

Properties of acoustic resonance in double-actuator ultra-sonic gas nozzle:numerical study

The ultra-sonic gas atomization （USGA） nozzle is an important apparatus in the metal liquid air-blast atomization process. It can generate oscillating supersonic gas effiux, which is proved to be effective to enforce the atomization and produce narrow-band particle distributions. A double-actuator ultra-sonic gas nozzle is proposed in the present paper by joining up two active signals at the ends of the resonance tubes. Numerical sim- ulations axe adopted to study the effects of the flow development on the acoustic resonant properties inside the Haxtmann resonance cavity with/without actuators. Comparisons show that the strength and the onset process of oscillation are enhanced remarkably with the actuators. The multiple oscillating amplitude peaks are found on the response curves, and two kinds of typical behaviors, i.e., the Hartmann mode and the global mode, are discussed for the corresponding frequencies. The results for two driving actuators are also investigated. When the amplitudes, the frequencies, or the phase difference of the input signals of the actuators are changed, the oscillating amplitudes of gas effiux can be altered effectively.

Repeatability and agreement of CCT measurement in myopia using entacam and ultrasound pachymetry

AIM: To evaluate the repeatability of central corneal thickness (CCT) measurement by entacam, and agreement of CCT measured by Pentacam and ultrasound pachymetry (USP) in Chinese myopia. Thereby investigate the possibility of Pentacam as a substitute for USP in CCT measurement before refractive surgery. The effects of corneal curvature measured by Pentacam on CCT were also evaluated. METHODS: One hundred and forty-eight right eyes of 148 individual with myopia were included in this study. Three successive Pentacam CCT measurements followed by 10 successive ultrasound pachymetry were carried out in the 148 eyes. Mean of CCT taken by each device was calculated for comparison. According to the CCT measured by USP, all the 148 eyes were divided into 3 groups: <520 mu m, 520-560 mu m, >560 mu m. For all eyes and each group the CCT obtained by Pentacam and USP were compared. Anterior corneal curvature of the 148 eyes was also adopted for correlation analysis with CCT obtained by ultrasound pachymetry. In addition, CCT measurement using 60 random selected Scheimpflug images was performed by 3 skilled investigators at different time, and this was repeated for 3 times by a forth investigator to assess repeatability of Pentacam CCT measurement using Scheimpflug images. RESULTS: Intraclass correlation coefficient (ICC) analysis revealed high intraobserver repeatability (ICC=0.994, F=158.60, P<0.001) for CCT measurement by Pentacam. The interobserver (ICC=0.998, F =494.73, P <0.001) and intraobserver (ICC=0.997, F=383.98, P<0.001) repeatability for Pentacam CCT measurements using Scheimpflug images were also excellent. There was high positive correlation between the CCT values measured by Pentacam and ultrasound pachymetry (r=0.963, P<0.001). Bland-altman plots showed that the Pentacam underestimate the CCT by 8.02 mu m compared with ultrasouond pachymetry.The differences between Pentacam and USP increased as the CCT readings by USP increased (Pentacam vs USP: slope=-0.04, P< 0.05). The 95% upper and lower limits of agreement between CCT values obtained from the two devices were +9. 33 mu m and -25.37 mu m. No significant association could be found between CCT and anterior corneal curvature. CONCLUSION: Inter- and intraobserver variability for CCT measurements by Pentacam was considerably below clinically significant levels. CCT of myopia obtained by Scheimpflug camera, Pentacam, were highly correlated to that by ultrasound pachymetry. However, the values obtained are not directly interchangeable between Pentacam and ultrasound pachymetry as the 95% limits of agreement are relatively wide. Pentacam can be a useful instrument for measuring CCT in candidates to refractive surgery in clinic.

Three-year follow-up in advanced pediatric keratoconus:thin corneas may not have pachymetry properly assessed after crosslinking

AIM:To analyze the crosslinking(CXL)effects in pediatric keratoconus,and to identify the patients’corneal characteristics whose pachymetry could not be adequately evaluated by Scheimpflug method after procedure.METHODS:Consecutive pediatric patients with progressive keratoconus underwent CXL were included.Best-corrected visual acuity(BCVA)and spheric equivalent(SE)were measured before and after CXL.After CXL,groups 1 and 2 were divided based on the posterior surface Pentacam quality specifications(QS):"OK"(Group 1)and"not OK"(Group 2).The mean(RmF and RmB)and minimum(RminF and RminB)radius of curvatures of the anterior and posterior corneal surfaces,and the thinnest pachymetry(Pmin)were measured preoperatively at 3,6,12,24,and 36 mo.Haze was annotated.RESULTS:Twenty-six patients(14 men,mean age 14±1.8 y)and median Kmax of 59.9 D initially and 61.4 D preoperatively were treated.BCVA was not different before and 24 mo after CXL.Group 2 statistically differed to group 1 in that SE was more myopic before and with no difference 24 mo after CXL;RmF and RmB were steeper and Pmin was thinner pre-surgically.Group 2,in which pachymetric changes could not be adequately evaluated after surgery,presented with significant RmF flattening,a shift to hyperopia,and more haze after CXL.CONCLUSION:Patients whose pachymetry could not be adequately evaluated after CXL had steeper and thinner corneas before surgery.The predictive factors for impaired QS after CXL are RmF,RmB,and Pmin.In advanced keratoconus,alternative methods to analyze pachymetry and the posterior surface should be considered.

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.

Repeatability of 3D OCT Pachymetry in Eyes with and without Contact Lens Induced Corneal Swelling

Introduction: Corneal thickness measurement is an indirect assessment of the physiological corneal function in human eye. This value, especially in the central area, is an important data for clinical diagnosis, treatment and monitoring of anterior segment pathologies. There are several technologies for non-invasively measuring corneal thickness like optical coherence tomography (OCT). However, there is little information available describing the effect of contact lens induced corneal swelling in OCT measures. The purpose of this study was to evaluate the repeatability of OCT corneal pachymetry in eyes with and without contact lens induced corneal swelling. Material and Methods: This study included five visits over one week in six healthy subjects: baseline and after sleeping with four different CL of +0.50 D, +2.00 D, +5.00 D and +8.00 D (Acuvue 2, Johnson & Johnson Vision Care) on four different days. Corneal pachymetry OCT 3D (Topcon) were measured three consecutive times during each visit. Besides, this measurement was repeated in 12 meridians (Scans #1 to #12), between 0°and 165°with 15° intervals. Results: Corneal pachymetry was significant different between before and after contact lens wear (p < 0.001 ANOVA). High repeatability was found without corneal swelling [Coefficient of variation (CV) = 0.68% p = 0.93] and with corneal swelling [CL -0.50 D (CV = 0.78% p = 0.95;590 ± 46 μm CI 95% 548 to 596), with CL + 2.00 D (CV = 0.72% p = 0.97;601 ± 46 μm CI 95% 595 to 607), with CL + 5.00 D (CV = 0.78% p = 0.66;608 ± 50 μm CI 95% 601 to 615) and with CL + 8.00 D (CV = 0.77% p = 0.97;607 ± 44 μm CI 95% 601 to 613)]. There were no differences (p = 1.00) in central corneal thickness along the 12 scans corneal [Scan #0 (593 ± 50 μm CI 95% 582 to 603), #1 (592 ± 50 μm CI 95% 581 to 603), #2 (591 ± 50 μm IC 95% 580 to 602), #3 (590 ± 49 μm CI 95% 579 to 600), #4 (590 ± 50 μm CI 95% 579 to 600), #5 (591 ± 50 μm CI 95% 581 to 602), #6 (590 ± 51 μm CI 95% 580 to 601), #7 (589 ± 50 μm CI 95% 578 to 600), #8 (590 ± 50 μm CI 95% 579 to 600), #9 (589 ± 50 μm CI 95% 579 to 600), #10 (592 ± 50 μm CI 95% 581 to 602) and #11 (591 ± 50 μm CI 95% 580 to 601). Conclusions: 3D OCT showed a high repeatability (CV < 1%) to measure central thickness in corneas with and without contact lens induced corneal swelling. This technology presents advantages over other clinical devices used to measure corneal thickness and could be the “gold standard” for future clinical studies and clinical practice for eye care practitioners.

Comparison of Central Corneal Thickness using Ultrasound Pachymetry during Corneal Collagen Cross-linking

Purpose:To study variation in central corneal thickness (CCT) during corneal collagen cross-linking(CXL) using ultrasound pachymetry. Methods:Twenty patients (26 eyes) with progressing keratoconus undergoing riboflavin-UVA-induced CXL were involved in this study. Intraoperative CCT measurement using ultrasonic pachymetry was performed during the procedure.Measurements were obtained before operation, after epithelial removal, after riboflavin drop instillation, and after UVA irradiation. Results:Mean CCT was 495±56 and 450±52 μm before and after epithelial removal, respectively. Mean CCT was 443±42 and 411±39 μm after riboflavin drop instillation and after UVA irradiation, respectively. Statistically significant decreases in CCT occurred between the preoperative period and after epithelial removal, after riboflavin drop instillation and after UVA irradiation. Twenty-six eyes from 20 patients undergoing CXL were divided into 2 groups (I with CCT≥400 μm after UVA irradiation and II with CCT<400 μm after UVA irradiation). No statistically significant difference was noted between I and II in preoperative endothelial cell count, but a statistically greater postoperative endothelial cell count was noted in I compared to II. A statistically significant difference was evident between preoperative and postoperative endothelial cell counts in Group II (P<0.05). Conclusion:Performing CXL with the use of riboflavin and UVA irradiation resulted in a statistically significant decrease in CCT, to a level where the corneal endothelium may be damaged.(Eye Science 2013; 28:15-19)

Evaluation of corneal parameter changes under different accommodative stimuli with Scheimpflug imaging-based tomography

AIM:To evaluate the reliability of measurements of corneal changes with accommodation in healthy eyes using a Scheimpflug imaging-based system and how these measurements distribute in the normal population.METHODS:Prospective,non-randomized,comparative study including 27 healthy subjects(54 eyes),including emmetropia(13 eyes),myopia(17 eyes),hyperopia(4 eyes)and astigmatism(20 eyes)groups.In all cases,a complete eye examination was performed,including the analysis of corneal changes with different accommodative stimuli(+2.00,0.00 and-3.00 D)using the Pentacam AXL system.The investigation was structured in 2 phases:repeatability analysis and characterization of accommodation-related corneal changes in healthy populations.RESULTS:In the repeatability analysis,the index of height asymmetry(IHA)showed the greatest variability with the three accommodative stimuli,being the results for the rest of parameters acceptable.The group of emmetropes showed significant differences with accommodative changes in the position of maximum keratometry(Kmax;P<0.05),whereas in the astigmatism group,significant changes were not only observed in the position of Kmax,but also in minimum corneal thickness(MCT),corneal spherical aberration,and total and low order aberration root mean square(all P<0.05).Likewise,a significant difference was found in the displacement of the X position of Kmax with+2.00 D and-3.00 D in the myopia group(P=0.033)as well as in changes with+2.00 D and-3.00 D in the magnitude of the position vector of Kmax in the emmetropia group(P<0.05).No significant changes were found between accommodative stimuli in the displacement of coordinates of MCT(P≥0.109).CONCLUSION:The position of Kmax and MCT in healthy corneas can change significantly when presenting different accommodative stimuli using the accommodation mode of the Pentacam system,with different trends in these accommodation-related corneal changes between refractive errors.Likewise,the consistency of the measurements obtained with Scheimpflug has been confirmed.

角膜厚度的临床意义及测量方法进展

角膜厚度在角膜屈光手术术前检查中越来越受到眼科医师的重视。目前用于测量角膜厚度的仪器很多,大概分为两类:一类是基于超声波原理,有传统的超声测厚仪和超声生物显微镜;一类是基于光学原理,有Orbscan(Orbscan裂隙扫描角膜地形图/角膜测厚系统)、Pentacam(Pentacam眼前节综合分析系统)、OCT(optical coherence tomography,包括时域OCT,傅里叶域OCT)、角膜内皮镜及Lenstar等。各种检查方法都有其优点,也有其不足之处。但是,角膜厚度测量方法发展的趋势是简单易用,非接触性,重复性好,准确性好。本文旨在介绍角膜厚度的临床意义及测量方法新进展,并对各种测量方法进行分析总结,以供眼科医生在临床工作中参考。

急性闭角型青光眼眼压下降后中央角膜厚度与慢性闭角型青光眼的比较

目的采用前瞻性非随机对照研究比较急性闭角型青光眼和慢性闭角型青光眼的中央角膜厚度和眼部其他参数的异同。方法观察75例急性闭角型青光眼和69例慢性闭角型青光眼患者的中央角膜厚度。眼压控制后每例患者接受A超检查,检查项目包括中央角膜厚度、中央前房深度、晶状体厚度和眼轴长度。统计分析采用t检验。结果急性闭角型青光眼患者的平均中央角膜厚度是(576.97±50.93)μm,慢性闭角型青光眼患者为(543.35±35.85)μm,两组之间中央角膜厚度差异有统计学意义(P<0.001)。急性闭角型青光眼对侧眼中央角膜厚度为(544.68±33.53)μm,比急性发作眼薄,对侧眼与慢性闭角型青光眼中央角膜厚度之间差异无统计学意义(P=0.818)。急性闭角型青光眼患者眼轴长度为(21.71±1.14)mm,慢性闭角型青光眼为(22.20±1.21)mm,两组之间的眼轴长度差异有统计学意义(P=0.014)。急性闭角型青光眼前房深度(2.42±0.39)mm,慢性闭角型青光眼为(2.45±0.31)mm,急性闭角型青光眼组晶状体厚度(4.84±0.39)mm,慢性闭角型青光眼组为(4.81±0.43)mm。两组之间的前房深度和晶状体厚度差异均无统计学意义(均为P>0.05)。结论与慢性闭角型青光眼相比,急性闭角型青光眼的中央角膜厚度较厚,可能是急性高眼压后角膜水肿造成,而前房浅、眼轴短可能是其急性发病的原因之一。

角膜厚度的测量方法及其临床进展

20世纪50年代以来,随着角膜厚度在青光眼诊断治疗中的地位不断突出以及近年来屈光手术的蓬勃发展,角膜厚度测量日益受到了学者的关注,测量仪器不断推陈出新,测量结果亦更合理准确。目前可用于角膜厚度测量的仪器很多,本文就当前临床上常用的几种测量仪器的特点及其进展做一综述。

Lenstar及Pentacam与A超测量白内障患者眼生物参数的比较（英文）

目的:比较光学相干生物测量仪(Lenstar)、三维眼前节分析仪(Pentacam)和A型超声测量仪(A-scan)在白内障患者中测量角膜中央厚度、角膜曲率、前房深度和眼轴长度结果的差异。方法:分别用3种仪器对158例(158眼)白内障患者进行眼部生物测量,比较角膜中央厚度、角膜曲率、前房深度和眼轴长度的结果,采用重复测量的方差分析及Pearson相关分析,一致性比较采用Bland-Altman统计分析法。结果:Lenstar和Pentacam测得的角膜中央厚度分别为536.54±27.90μm和541.46±29.85μm,两者差异有统计学意义(t=-5.439;P<0.001);K值分别为43.87±1.45D和43.86±1.44 D,两者差异无明显统计学意义(t=-0.348,P>0.05)。Pentacam、Lenstar和A超测量的前房深度分别是2.73±0.38mm、2.71±0.38mm和2.85±0.40mm,三者差异均有统计学意义(F=309.94,P<0.001),Pearson相关分析显示三者呈正相关(r=0.989,0.978,and 0.977;P<0.001),但变异系数较小(CV=3.12%)。A超和Lenstar测量的眼轴长度分别是24.28±1.70mm和24.52±1.73mm,两者差异有统计学意义(t=-19.482,P<0.001,r=0.996;P<0.001)。BlandAltman分析显示,对于这几种眼前节参数,三种方法测量的一致性较好。结论:三种仪器测量的结果尽管有一定差异,但Lenstar和Pentacam的生物测量可重复性好,操作简便更易用于白内障患者的检查。

前节OCT和pentacam及A超在测量角膜厚度上的比较

目的:对比分析前节OCT、pentacam三维眼前节分析仪及A超在测量角膜厚度上的差异性。方法:回顾研究2013-01/05在我院行准分子激光近视矫正手术的患者43例86眼。利用前节OCT、pentacam以及A超测量患者的角膜厚度,对三组数据对比分析,利用配对t检验以及相关分析进行统计学分析。结果:前节OCT、pentacam及A超测量患者的中央角膜厚度分别为535±52,550±52,550±51μm。配对t检验提示前节OCT和pentacam及A超测量结果均具有统计学差异(P<0.01),而pentacam和A超测量结果配对t检验提示无统计学差异(P=0.82)。三种测量结果均具有显著相关性,其相关性依次为:pentacam和A超为0.998,前节OCT和A超为0.993,而前节OCT和pentacam为0.991(P<0.01)。结论:前节OCT测量角膜中央厚度结果偏薄,而pentacam测量结果和作为金标准的A超结果相近。

Pentacam和Sirius地形图系统与超声测厚仪角膜厚度的对比研究

目的:探讨Sirius与Pentacam及超声测厚仪测量中央角膜厚度的一致性。方法:对51例102眼正常人采用Pentacam和Sirius及超声角膜测厚仪三种仪器测量角膜厚度,记录并比较三种方法测量所得中央角膜厚度结果,同时运用Bland-Altman法绘制图表分析两两间一致性。结果:A超中央角膜厚度平均值低于Pentacam的平均值,Sirius中央角膜厚度的平均值最接近A超平均值。Sirius与Pentacam一致性的比较:其Bland-Altman图中3.92%的点在95%一致性界限以外。在一致性界限以内,Sirius与Pentacam中央角膜厚度差值的绝对值最大为19.5μm。Sirius与A超一致性的比较:其Bland-Altman图中2.94%的点在95%一致性界限以外。在一致性界限以内,Sirius与A超中央角膜厚度差值的绝对值最大为18.667μm。Pentacam与A超一致性的比较:其Bland-Altman图中5.82%点在95%一致性界限以外。在一致性界限以内,Pentacam与A超中央角膜厚度差值的绝对值最大为25.33μm。结论:Sirius系统与Pentacam系统具有良好的一致性,且Sirius系统比Pentacam系统更接近A超角膜测厚的结果。

Pentacam系统测量正常人眼表面麻醉前后中央角膜厚度的对比研究

目的比较Pentacam三维眼前节分析系统与A超角膜测厚仪测量正常人中央角膜厚度的差异,并研究Pentacam系统与A超测量正常人眼表面麻醉前后中央角膜厚度的变化,为临床角膜屈光手术方式的选择提供参考。方法对25例(50眼)正常人分别应用Pentacam系统及A超角膜测厚仪测量中央角膜厚度,Pentacam系统的测量时间包括使用表面麻醉药前及使用表面麻醉药后,并对检查结果进行统计学分析。结果使用表面麻醉药前Pentacam系统和A超测得的中央角膜厚度分别为(544.50±26.24)μm和(544.84±28.02)μm,两种方法测量的结果差异无统计学意义(P>0.05),两种测量结果之间具有密切相关性(P<0.001)。Pentacam系统测量正常人在表面麻醉前后中央角膜厚度结果差异有统计学意义(P<0.01),表面麻醉后的厚度为(549.76±27.09)μm,表面麻醉前后测量结果具有密切的相关性(P<0.001)。A超表面麻醉前后测量差异无统计学意义(P=0.765)。结论用Pentacam三维眼前节分析诊断系统进行中央角膜厚度的测量,结果准确、全面、方便,具有较好的临床应用价值;Pentacam系统测得的麻药前后中央角膜厚度有变化,表面麻醉后所测得的中央角膜厚度较表面麻醉前略增加,不具显著临床意义,对临床角膜屈光手术方式的选择无明显影响。

同轴微切口白内障超声乳化吸除术对角膜散光影响研究

目的:观察和比较1.8mm透明角膜微切口与3.2mm透明角膜小切口白内障超声乳化吸除术后对角膜散光的影响。方法:选取行白内障超声乳化人工晶体植入术的年龄相关性白内障患者85例117眼,将患者按随机数字表法分为两组。微切口组59眼行1.8mm同轴白内障超声乳化吸除术,小切口组58眼行3.2mm同轴白内障超声乳化吸除术。术前、术后1d、术后7d、术后30d和术后90d分别进行LogMAR视力、中央角膜厚度和角膜散光检查。比较两组术前和术后不同时间点各项检查结果的差异。结果:术后1d微切口组比小切口组视力恢复快,差异具有统计学意义(P<0.05),余时间点两组间视力差异无统计学意义(P>0.05)。术后各时间点微切口组和小切口组的中央角膜厚度增厚差异无统计学意义(P>0.05)。术后各时间点微切口组和小切口组的手术源性散光差异有统计学意义(P>0.05),两组均在术后30d角膜散光趋于稳定。结论:与3.2mm小切口白内障超声乳化吸除术相比,同轴1.8mm微切口白内障超声乳化吸除术的手术源性散光小,术后视力恢复快。

Cirrus HD-OCT测量近视患者角膜厚度的应用研究

目的对比分析Cirrus HD-OCT和A超测量中央角膜厚度的差异性及相关性,并探索Cirrus HD-OCT角膜测厚与眼轴长度的关系。方法回顾性研究2015年1月至4月拟在我院行角膜激光矫正近视手术的患者42例（84眼）,按眼轴长度分为三组,A组（32眼）：眼轴长度24~26 mm组;B组（31眼）：眼轴长度〉26~28 mm组;C组（21眼）：眼轴长度〉28 mm组。利用Cirrus HD-OCT和A超分别测量患者的中央角膜厚度,用配对t检验来比较两种方法测厚的差异性,用Pearson分析两种方法测厚的相关性,用两独立样本t检验比较不同眼轴组角膜厚度的差异性。结果 A组Cirrus HD-OCT和A超测量患者的中央角膜厚度分别为（539.91±30.74）μm和（540.22±30.79）μm,测量结果差异无统计学意义（t=0.230,P〉0.05）。B组Cirrus HDOCT和A超测量患者的中央角膜厚度分别为（543.94±31.75）μm和（544.36±33.58）μm,测量结果差异无统计学意义（t=0.304,P〉0.05）。C组Cirrus HD-OCT和A超测量患者的中央角膜厚度分别为（548.19±25.81）μm和（545.43±26.70）μm,测量结果差异也无统计学意义（t=1.766,P〉0.05）。Cirrus HD-OCT和A超测量结果具有显著正相关性（r=0.97,P〈0.05）。三组间Cirrus HD-OCT角膜测厚的差异性比较,A组与B组测量值差异无统计学意义（t=0.504,P〉0.05）、A组与C组测量值差异无统计学意义（t=0.999,P〉0.05）、B组与C组测量值差异无统计学意义（t=0.499,P〉0.05）。Cirrus HD-OCT测量角膜厚度与眼轴长度无相关性。结论 Cirrus HD-OCT测量中央角膜厚度结果可靠,且Cirrus HD-OCT和A超的测量结果显著的正相关。Cirrus HD-OCT角膜测厚与眼轴长度无关。

Pentacam分析仪测量近视眼患者角膜厚度及影响因素分析

目的使用Pentacam眼前节分析系统测量近视患者角膜中央最薄点厚度,并探讨与A型超声角膜测厚仪测量结果的差异及可能影响因素。方法对预行准分子激光角膜手术的近视患者150例(300眼),分别采用Pentacam系统及A型超声角膜测厚仪测量角膜中央最薄点厚度,对测量结果进行统计学分析。结果 Pentacam、A型超声角膜测厚仪测得的中央角膜最薄点厚度平均值分别为(543.7±26.3)μm、(539.2±27.4)μm,二者高度相关(r=0.97,P=0.0001)。Pentacam测得角膜厚度值偏厚,二者差值平均(4.4±7.0)μm,差异有统计学意义(t=10.94,P=0.0001),该差值与A型超声测量角膜厚度值、年龄有关(P=0.0001),而与屈光度、性别、角膜直径、角膜曲率等无关。结论 Pentacam测量近视患者角膜厚度值略高于A型超声角膜测厚仪,尽管二者有很好的协同性,但相互间还不能完全替代。

麻醉剂和泪膜对健康人角膜厚度的影响

目的 :探讨影响Orbscan角膜测厚准确性的各种因素 ,以期提高Orbscan测量精度。方法 :分别用Orbscan和A超测厚仪测量 6 3例正常志愿者 (12 6只眼 )的角膜中央厚度 (CCT) (角膜光学中心点厚度 )。正常志愿者本身情况做对照组。然后改变实验条件测量正常志愿者 ,得到以下几组 :①表麻剂组 (TA group) :双眼点表面麻醉剂后 1min、5min、10min、15min、2 0min、2 5min和 30min后 ,用Orbscan测量CCT ,重复三次 ,取均值。②角膜前泪膜组 (PTF group) :分收稿日期 :2 0 0 4-0 2 -0 8;修回日期 :2 0 0 4-0 4-2 5基金项目 :内蒙古医学院研究生基金课题 (2 0 0 10 77)。作者简介 :李坤 (1972 -) ,男 ,山东东营人 ,医学硕士 ,研究方向 :临床视光学和青光眼。E -mail:LK112 5cn @hotmail.comA、B两组。点表麻剂 1min后用无菌吸水海绵签移除角膜前泪膜后 (A组 )以及用无菌玻璃棒刺激结膜产生反应性流泪(B组 )后 10s、10min、2 0min和 30min时 ,用Orbscan和A超测量CCT ,各重复三次 ,取均值。结果 :用Orbscan和A超测厚仪测得正常志愿者平均CCT分别为 (5 39.3± 4 0 .7) μm和(5 4 7.3± 38.6 ) μm。点表麻剂后中央角膜厚度较正常对照组增加 ,且随时间呈抛物线性关系。

角膜生物力学分析仪测量近视患者中央角膜厚度和眼压的准确性评价

背景CorvisST角膜生物力学分析仪（CorvisST）能测量角膜生物力学指标、眼压和中央角膜厚度（CCT），且测量的眼压值为校正CCT和生物力学因素的修正值，在国外已用于临床，但目前对中国人群CCT和眼压测量准确性的研究报道较少。目的评估CorvisST测量近视患者CCT和眼压的准确性，为其临床应用提供参考。方法采用诊断性试验方法，对2012年11—12月在广西视光中心准分子激光门诊行术前检查的56例近视患者进行CorvisST、Goldmann压平式眼压计（GAT）和A型超声检查，采用配对t检验法比较CorvisST测量CCT值与A型超声测量结果的差异及CorvisST测量眼压值与GAT测量结果的差异，采用Bland·Altman法评价不同测量方法测量结果的一致性。结果CorvisST测得的CCT值为（539．82±19．79）μm，高于A型超声测量的CCT值（535．34±19．41）μm，两者比较差异有统计学意义（￡：4．19，P〈O．01）。CorvisST测得CCT均值较A型超声测量均值高4．5μm，95％的一致性界限为-11．2～20．2Ixm，7．1％（4／56）的点在95％的一致性界限以外。CorvisST和GAT测得的眼压值分别为（15．75±1．60）mmHg（1mmHg=0．133kPa）和（16．23±2．40）mmHg，两者比较差异有统计学意义（t=2．15，P=0．04）。CorvisST测得的眼压均值较GAT测得均值低0．5mmHg，95％一致性界限为-3．8—2．8mmHg，3．57％（2／56）的点在95％一致性界限以外。结论CorvisST测量的CCT稍高于A型超声，2种检测仪器测量的CCT结果一致性较差，临床上不可互相代替。CorvisST测量的眼压值稍低于GAT，二者测量值具有较好的一致性，临床上可以互相替代。