Effect of axial length and anterior chamber depth on the peripheral refraction profile

AIM:To evaluate the effect of axial length(AL)and anterior chamber depth(ACD)on peripheral refractive profile in myopic patients compared to emmetropic participants.METHODS:This cross-sectional study was conducted in right eyes of 58 participants of whom 38 were emmetropic and 20 were myopic.Central and peripheral refraction were measured at 10°,20°,and 30°eccentricities in nasal and temporal fields using an open-field autorefractor.The Lenstar LS900 was used to measure ACD and AL.The participants were divided into three groups of short(<22.5 mm),normal(22.5-24.5 mm),and long eye(>24.5 mm)according to AL and three groups of low ACD(<3.00 mm),normal ACD(3.00-3.60 mm),and high ACD(>3.60 mm)according to ACD.RESULTS:The mean age of the participants was 22.26±3.09 y(range 18-30 y).The peripheral mean spherical refractive error showed a hypermetropic shift in myopic and emmetropic groups although this shift was more pronounced in the myopic group.The results showed significant changes in the spherical equivalent,J0,and J45 astigmatism in all gazes with an increase in eccentricity(P<0.001).The pattern of refractive error changes was more noticeable in long and short eyes versus normal AL eyes.Moreover,the pattern of peripheral refractive changes was much more prominent in the high ACD group versus the normal ACD group and in the normal ACD group versus the low ACD group.CONCLUSION:Peripheral refraction changes are greater in participants with AL values outside the normal range and deeper ACD values compared to participants with normal AL and ACD.

Axial length,vitreoretinal pathology,and anterior chamber depth can predict postoperative refractive outcomes in phacovitrectomy/silicone oil removal

AIM:To evaluate the postoperative refractive prediction error(PE)and determine the factors that af fect the refractive outcomes of combined pars plana vitrectomy(PPV)or silicone oil removal(SOR)with cataract surgery.METHODS:The study is a retrospective,case-series study.Totally 301 eyes of 301 patients undergoing combined PPV/SOR with cataract surgery were enrolled.Eligible individuals were separated into four groups according to their preoperative diagnoses:silicone oil-filled eyes after PPV(group 1),epiretinal membrane(group 2),macular hole(group 3),and primary retinal detachment(RD;group 4).The variables af fecting postoperative refractive outcomes were analyzed,including age,gender,preoperative best-corrected visual acuity(BCVA),axial length(AL),keratometry average,anterior chamber depth(ACD),intraocular tamponade,and vitreoretinal pathology.The outcome measurements include the mean refractive PE and the proportions of eyes with a PE within±0.50 diopter(D)and±1.00 D.RESULTS:For all patients,the mean PE was-0.04±1.17 D,and 50.17%of patients(eyes)had a PE within±0.50 D.There was a significant difference in refractive outcomes among the four groups(P=0.028),with RD(group 4)showing the least favorable refractive outcome.In multivariate regression analysis,only AL,vitreoretinal pathology,and ACD were strongly associated with PE(all P<0.01).Univariate analysis revealed that longer eyes(AL>26 mm)and a deeper ACD were correlated with hyperopic PE,and shorter eyes(AL<26 mm)and a shallower ACD were correlated with myopic PE.CONCLUSION:RD patients have the least favorable refractive outcome.AL,vitreoretinal pathology,and ACD are strongly associated with PE in the combined surgery.These three factors affect refractive outcomes and thus can be used to predict a better postoperative refractive outcome in clinical practice.

Axial length and anterior chamber indices in elderly population: Tehran Geriatric Eye Study

AIM:To determine the normative distribution of axial length(AL),anterior chamber depth(ACD),anterior chamber volume(ACV),anterior chamber angle(ACA),and some of their associated factors in subjects aged 60 and over.METHODS:In this cross-sectional study,160 clusters were sampled using multi-stage cluster sampling in Tehran,Iran.After a preliminary interview,the participants underwent optometric examinations including visual acuity and refraction measurement followed by slit lamp biomicroscopy.Finally,ocular imaging was done using the Pentacam AXL to measure AL,ACD,ACV,and ACA.RESULTS:A total of 4519 eyes of 2436 participants were evaluated,of whom 58.0%(n=1412)were female.The mean age of the subjects was 67.32±6.05y(range:60-95y).The mean AL,ACD,ACV,and ACA was 23.22 mm(23.18-23.27 mm),2.61 mm(2.59-2.62 mm),126.56 mm3(125.08-128.04 mm3),and 30.61°(30.3°-30.92°),respectively.In the multivariable model,after adjusting for the effect of both eyes,the longest and shortest AL was seen in myopic and hyperopic subjects,respectively.AL,ACD,ACV and ACA were significantly larger in men compared to women(P<0.001).Except ACA,other evaluated parameters showed an inverse correlation with age(P<0.001),however,this correlation was insignificant for AL(P=0.623).CONCLUSION:Normative value of AL,and other biometric parameters are specific for each ethnicity,age and sex group.Any alteration in these parameters and their effect on refraction should be considered in this age group,especially in case of cataract surgery.

Distribution of Axial Length, Anterior Chamber Depth and Lens Thickness of Pre-Operative Cataract Patients in Indonesian Population

Purpose: Biometry measurement of pre-operative cataract patients plays a major role in calculating intraocular lens power. This study aimed to review and determine the distribution of biometry components, such as axial length (AL), anterior chamber depth (ACD), and lens thickness (LT) of pre-operative cataract patient in Indonesian population. Methods: A cross-sectional study data were obtained from 2015-2018 cataract surgery at Prima Husada Citra Hospital, Surabaya, East Java, Indonesia. A total of 1295 eyes with cataract was included in the study based on their medical record. We analyzed the data using descriptive analysis and correlated each variable using the Spearman’s Rho analysis. Results: Mean AL, LT and ACD was 23.81 ± 1.46 mm, 4.49 ± 0.55 mm, 3.25 ± 0.70 mm respectively. Male has longer AL and deeper ACD with (p < 0.001), while LT was found thicker in female (p = 0.005). The increase of AL was accompanied by ACD (r = 0.457;p < 0.001) and a thinner LT (r = -0.101;p < 0.001). Conclusions: LT is increased with age while AL and ACD are shortened with age. There was a positive correlation between AL and ACD, but an inverse correlation between AL and LT.

Chemoattractive capacity of different lengths of nerve fragments bridging regeneration chambers for the repair of sciatic nerve defects

A preliminary study by our research group showed that 6-mm-long regeneration chamber bridging is equivalent to autologous nerve transplantation for the repair of 12-mm nerve defects. In this study, we compared the efficacy of different lengths （6, 8, 10 mm） of nerve fragments bridging 6-mm regeneration chambers for the repair of 12-mm-long nerve defects. At 16 weeks after the regeneration chamber was implanted, the number, diameter and myelin sheath thickness of the regenerated nerve fibers, as well as the conduction velocity of the sciatic nerve and gastrocnemius muscle wet weight ratio, were similar to that observed with autologous nerve transplantation. Our results demonstrate that 6-, 8-and 10-mm-long nerve fragments bridging 6-mm regeneration chambers effectively repair 12-mm-long nerve defects. Because the chemoattractive capacity is not affected by the length of the nerve fragment, we suggest adopting 6-mm-long nerve fragments for the repair of peripheral nerve defects.

Associations of lens thickness and axial length with outcomes of laser peripheral iridotomy

AIM:To investigate the association of axial length(AL),lens thickness(LT),and lens vault(LV)with postoperative anterior chamber angle metrics after laser peripheral iridotomy(LPI).METHODS:Prospective observational study of 69 patients(97 eyes)were diagnosed as primary angle-closure suspect(PACS),primary angle closure(PAC)or primary angle-closure glaucoma(PACG).AL,LT,anterior central chamber depth(ACD),angle opening distance(AOD),trabecular iris angle(TIA),and angle recess area(ARA)were measured before and 1 wk after LPI.The association between AL,LT,LV with ACD,AOD,TIA,ARA were analyzed by comparing the differences between preoperative and postoperative measurements for anterior segment biometric parameters.RESULTS:ACD,AOD,TIA,and ARA were significantly increased after LPI(all P<0.05).Greater LT was significantly associated with greater postoperative increases in ACD,AOD,TIA,and ARA(all P<0.05).AL was not significantly associated with changes of anterior segment biometric parameters.Greater LV was significantly associated with greater postoperative increases in ACD,AOD,and TIA(all P<0.05),but was not significantly associated with changes of ARA.CONCLUSION:Greater baseline LT and LV measurements are associated with greater increases in anterior segment biometric parameters after laser peripheral iridotomy.AL are not associated with the change of anterior segment biometric parameters.

Ultrasonic Evaluation of the Lens Thickness to Axial Length Factor in Primary Closure Angle Glaucoma

Ultrasonic biometry was done in 232 normal eyes and 138 eyes with primary angle closure glaucoma (ACG), using Ultrascan Digital B System IV (10 MHz). The ratio between the lens thickness and the axial length (lens thickness to axial length factor, LAF) was evaluated as a biometric index for assessing the eye with primary ACG in Chinese. LAF of 2.00 was found to be ideal point of demarcation between ACG and normal eyes (i.e., lens thickness equals to 1/5 of axial length). It appears that LAF is helpful i...

Turbulence statistics of natural airflow within a large Open Top Chamber

The turbulence statistics parameters （variables） of natural airflow within a large Open Top Chamber （OTC）, 4 m in high height and 3 m in diameter, were measured with a three-dimensional ultrasonic anemometer/thermometer at Research Station of Changbai Mountain Forest Ecosystems Jilin Province, China in May 2004, for improving the field application of OTP. Results showed that because of the physical limitation, turbulence within OTC exhibited unique map compared with that of natural environments. There were clear daily pat- terns for most parameters. Turbulence here seemed to be isotropic and closely linked at all directions. Shape of eddies looked like a ＇cylinder＇ which was very similar to the shape of OTC. Continuous airflow was always interpreted by large scale eddies from top of OTC and showed high interactive intermittence at all directions.

Optimization Analysis of the Mixing Chamber and Diffuser of Ejector Based on Fano Flow Model

An improved model to calculate the length of the mixing chamber of the ejector was proposed on the basis of the Fano flow model,and a method to optimize the structures of the mixing chamber and diffuser of the ejector was put forward.The accuracy of the model was verified by comparing the theoretical results calculated using the model to experimental data reported in literature.Variations in the length of the mixing chamber L_(m) and length of the diffuser L_(d) with respect to variations in the outlet temperature of the ejector T_(c),outlet pressure of the ejector p_(c),and the expansion ratio of the pressure of the primary flow to that of the secondary flow p_(g)/p_(e) were investigated.Moreover,variations in L_(m) and L_(d) with respect to variations in the ratio of the diameter of the throat of the motive nozzle to the diameter of the mixing chamber d_(g0)/d_(c3) and ratio of the outlet diameter of the diffuser to the diameter of themixing chamber d_(c)/d_(c3) were investigated.The distribution of flow fields in the ejector was simulated.Increasing L_(m) and d_(c3) reduced T_(c) and p_(c).Moreover,reducing p_(g)/p_(e) or d_(g0)/d_(c3) reduced T_(c) and p_(c).The length of the mixed section L_(m2),which was determined on the basis of the Fano flow model,increased as pg increased and decreased as d_(c3) increased.The mixing length L_(m1),which was considered the primary flow expansion,showed the opposite trend with that of L_(m2).Moreover,Ld increased as p_(g)/p_(e) and d_(c)/d_(c3) increased.When the value of d_(c) was 1.8 to 2.0 times as high as that of dc3,the semi-cone angle of the diffuser ranged between 6°and 12°.At a constant dc/dc3,decreasing T_(c) and pc increased Ld.

New Materials for Vacuum Chambers in High Energy Physics

Vacuum chambers must fulfil ultra-high vacuum requirements while withstanding thermo-mechanical loads. This is particularly true in high energy particle accelerator where interactions of particles with matter may induce thermal load, material activation, background… The choice of the material of the vacuum chamber is crucial for the final application. Metals such as stainless steel, copper and aluminium are usually used. Even with outstanding mechanical and physical properties, beryllium is used for very specific applications because of its cost and toxicity.Ceramics such as alumina are usually used for fast magnet vacuum chambers. With the next generation of high energy physics accelerator generation such as CLIC and TLEP, the problematic of high cyclic thermal load induced by synchrotron radiation is raised. This paper aims at defining some figures of merit of different materials with respect to several load scenarios and presents briefly their vacuum compatibility.

喷嘴距及混合室喉部长度对喷射器性能综合影响研究

在实际环境条件下,采用变几何喷射器是提高喷射器性能的重要途径。基于喷嘴距可调式的喷射器实验测试平台,采用实验和数值分析相结合的方法,研究不同无量纲混合室喉部长度下,无量纲喷嘴距对喷射器的性能及不可逆性影响。结果表明:在测试范围内,喷射器的临界喷射系数随着喷嘴距的增加先增加后减小,当达到最佳无量纲喷嘴距5.83时,临界喷射系数达到最大值0.45,合理的喷嘴距应避免激波链出现在混合室收缩段;喷射器的临界冷凝压力随喷嘴距的增加逐渐下降,当无量纲混合室喉部长度为4时,其临界冷凝压力下降7.36%,下降速度最慢,原因是较大的射流冲量提高了扩压室的压力恢复能力,使流体动能衰减速度有所减缓;当无量纲混合室喉部长度为4,无量纲喷嘴距为5.83时,热力学完善度达到最大值0.21;由喷嘴距引起的喷射器熵产主要来源于两股入口流在混合室收敛段的混合和第二冲击波向扩压室出口的移动,提高扩压室的压力恢复能力能有效避免熵产的急剧增加。研究结果对喷射器的结构及综合性能进行多目标优化,以减小喷射器不可逆性提供重要参考。

Insight into small eyes: a practical description from phenotypes presentations to the management

This narrative review aimed to have an algorithmic approach to microphthalmos by a systematic search.The definition can be related to a number of special phenotypes.In the more challenging cases of complex microphthalmos,relative anterior microphthalmos,and nanophthalmos,the surgeon can approach these cases more safely if they have a deep understanding of the anatomical variations and ideal formulae for intraocular lens computation and knows how to avoid intra-and post-operative complications.In this article,we review the criteria by which we recognize and describe pre-,intra-,and post-operative considerations,as well as discuss the ideal intraocular lenses for microphthalmos,given the intricate varieties of small eye phenotypes.

白内障手术候选者的眼部生物特征参数分析

目的:分析白内障手术候选人的眼部生物特征参数。方法:横断面研究。纳入2017-01/2021-09就诊于伊朗德黑兰Farabi眼科医院的4607例白内障患者(4607眼)。使用IOLMaster 700评估眼轴(AL)、角膜曲率(Kf、Ks、Km)、前房深度(ACD)。根据AL分为22 mm<AL、22 mm≤AL≤25 mm和AL>25 mm组,根据ACD分为3.00 mm<ACD、3.00 mm≤ACD≤3.60 mm、ACD>3.60 mm组。结果:患者平均年龄60.3±14.1(8-95)岁,女2243例(48.69%),男2364例(51.31%)。AL、ACD和平均角膜曲率范围分别为23.1-23.4 mm、3.1-3.2 mm和44.50-45.00 D。AL>25 mm组ACD平均值显著高于22 mm≤AL≤25 mm组和22 mm<AL组(P<0.001)。ACD>3.60 mm组的平均AL显著高于3.00 mm<ACD组和3.00 mm≤ACD≤3.60 mm组(P<0.001)。3.00 mm<ACD组和AL>25 mm组的Kf、Ks、Km均值显著高于ACD>3.60 mm组和22 mm<AL组(P<0.001)。结论:AL长的白内障患者ACD更深,角膜更平坦;AL短的患者ACD较浅,角膜较陡。此外,深ACD患者的AL较长,角膜较平坦,浅ACD患者的AL较低,角膜较陡。

中心性浆液性脉络膜视网膜病变眼部特征的研究进展

中心性浆液性脉络膜视网膜病变(CSC)是一种以特发性浆液性视网膜脱离(SRD)为特征的脉络膜视网膜疾病,伴有一处或多处视网膜色素上皮脱离(PED)或病变,具有特征性的眼球结构改变。CSC被归类为厚脉络膜相关疾病(PSD),近年来进一步发现主要为Haller层增厚。最近的研究重点关注了CSC患者的厚巩膜特征,阐述了其与脉络膜循环的密切关系,并提出CSC可能与葡萄膜渗漏综合征(UES)具有相似的发病机制。此外,CSC还具有短眼轴、远视性屈光不正、浅前房等特征,表明CSC不仅是眼球后极部的病变,而且累及全眼球。本文对CSC眼部特征的最新进展进行了综述,为进一步探究CSC发病机制提供新思路。

藏族年龄相关性白内障患者眼球生物学参数特征分析

目的:比较藏族与汉族年龄相关性白内障患者眼球生物学参数的差异,分析藏族患者眼球生物学参数的分布特征。方法:回顾性队列研究。收集2019-01/2020-12就诊于我院的年龄相关性白内障患者661例1 030眼,其中藏族患者483例739眼,汉族患者178例291眼。术前所有患者均采用IOL Master 500测量眼轴长度、前房深度、角膜曲率、散光及散光轴向。结果:藏族年龄相关性白内障患者眼轴长度为23.33(22.81,23.86)mm,前房深度为3.04(2.79,3.30)mm,散光度为0.73(0.47,1.07)D,平均角膜曲率为43.89±1.35 D,较汉族患者眼轴短,角膜曲率小(均P<0.05)。藏族患者的年龄与眼轴长度和前房深度均呈负相关,而与平均角膜曲率呈正相关(均P<0.05)。藏族患者中男性患者较女性患者眼轴更长、前房更深、角膜更平坦(均P<0.05)。结论:藏族与汉族年龄相关性白内障患者的眼球生物学参数存在差异,不同年龄和性别藏族患者眼球生物学参数的分布有所变化。

掺混腔室对透平性能影响的多工况对比研究

基于某变转速透平小机,采用数值模拟方法,研究了阀门全开和额定工况下,掺混腔室轴向长度对机组性能的影响,结果表明:随着掺混腔室轴向长度增加,级段效率逐渐提高,且额定工况效率增加的速度更快。掺混腔室轴向长度主要影响调节级(包含进汽室和掺混腔室)和第2级的性能。阀门全开工况下,随着掺混腔室轴向长度增加,调节级动叶域损失逐渐增大,但掺混腔室出口汽流均匀性得到改善,因此调节级效率逐渐降低,第2级效率逐渐提高。额定工况下,随着掺混腔室轴向长度增加,调节级动叶域损失逐渐减小,掺混腔室出口汽流均匀性得到改善,因此调节级和第2级效率均逐渐提高。

IOLMaster、Axis-ⅡA型超声和ODM1000A型眼科超声测量仪测量眼轴长度及前房深度的比较

背景眼轴长度和前房深度是人工晶状体（IOL）度数计算公式中的重要参数。目的对IOLMaster、Axis-ⅡA型超声、ODM1000A型眼科超声测量仪测量的眼轴长度及前房深度进行比较。方法同一操作者分别使用IOLMaster、Axis—UA型超声和ODM1000A型眼科超声测量仪测量48例83眼的眼轴长度及前房深度。结果Axis-ⅡA型超声、ODM1000A型眼科超声测量仪、IOLMaster测得眼轴长度的均值分别为（25．79±0．85）、（25．72±0．82）、（26．00±0．83）Film。Axis-ⅡA型超声比ODM1000A型眼科超声测量仪测得眼轴长度长（0．07±0．35）mm，差异无统计学意义（t=1．711，P=0．091）；IOLMaster比ODM1000A型眼科超声测量仪测得眼轴长度长（0．27±0．29）mm，差异有统计学意义（t=-8．570，P：0．000）；IOLMaster比Axis-ⅡA型超声测得眼轴长度长（0．21±0．32）mm，差异有统计学意义（t=-5．931，P=0．000）。3种检查仪测量眼轴长度结果相互呈正相关（r=0．916、0．938、0．928，P〈0．01）。Axis-ⅡA型超声、ODM1000A型眼科超声测量仪、IOLMaster测得前房深度分别为（3．81±0．21）、（3．84±0．25）、（3．83±0．18）mm。Axis-ⅡA型超声比ODM1000A型眼科超声测量仪测得前房深度值小（0．03±0．17）Film，差异无统计学意义（t=-1．324，P=0．189），IOLMaster比ODM1000A型眼科超声测量仪测得前房深度值小（0．01±0．15）mnl，差异无统计学意义（t=0．815，P=0．417），Axis-ⅡA型超声比IOLMaster测得前房深度值小（0．01±0．12）mm，差异无统计学意义（t=-0．900，P=0．371）。3种检查仪测量的前房深度值相互间均呈高度正相关（r=0．735、0．813、0．823，P〈0．01）。结论ODM1000A型眼科超声测量仪可以准确测量眼轴长度及前房深度，但不能替代10LMaster．

IOLMaster与接触式A超测量前房深度和眼轴长度的比较研究(英文)

目的:比较IOLMaster与接触式A超测量中央前房深度和眼轴长度的差异,以评价两者在人工晶状体度数计算参数测量中的准确性。方法:2006-10/2007-01在我院眼科施行白内障超声乳化摘除手术联合人工晶状体植入的患者121例(137眼),分别用IOLMaster与接触式A超于术前测量中央前房深度和眼轴长度。结果:IOLMaster与接触式A超测量中央前房深度分别为(2.94±0.49)mm,(2.58±0.51)mm,配对t检验,两者的差值为(0.36±0.30)mm(P<0.001),差异有显著性,相关系数r=0.823(P<0.001)。测量眼轴长度分别为(24.37±3.04)mm,(23.81±2.83)mm,配对t检验,两者差值为(0.56±0.34)mm(P<0.001),差异有显著性,相关系数r=0.996(P<0.001)。结论:IOLMaster与接触式A超均可用于前房深度和眼轴长度的测量,两者的相关性好。但基于光学原理的IOLMaster在准确测量眼轴长度和前房深度的同时,简便、快捷、非接触的特点是A超无法比拟的,并可同时测量出其他相关参数。

近视眼房角及相关组织结构形态的生物测量和分析

背景近视是全球范围内主要的致盲疾病之一，目前对近视眼结构的研究多集中于角膜曲率（CC）、中央角膜厚度（CCT）、前房深度（ACD）、眼轴长度（AL）、视网膜及脉络膜改变等方面，而对于近视眼眼前节结构，如前房角形态、睫状体形态等改变的研究少见报道。目的测量并分析近视眼房角及相关结构形态的改变。方法纳入2008年5月至2010年5月在青岛市第八人民医院确诊为正视或近视者149人，年龄18-40岁。受检者根据屈光度的不同分为正视组30人30眼、低度近视组46例46眼、中度近视组35例35眼和高度近视组38例38眼，平均屈光度分别为（0．02±O．18）、（-1．64±0．69）、（-4．56±0．66）和（-7．04±1．02）D；受检眼分别接受眼压、CC、AL测量及超声生物显微镜（UBM）和扩瞳验光等检查，观察各组间传统测量项目，如眼压、CCT、CC、AL、ACD及UBM测量指标，如房角开放距离（AOD）、虹膜厚度（ITl、IT2、IT3）、睫状体位置[A角、B角、小梁一睫状突距离（TCPD）、虹膜一睫状体距离（ICPD）]、睫状体厚度（CBTl、CBT2、CBT3）的差异。结果正视组、低度近视组、中度近视组和高度近视组间眼压、CC、CCT值出现轻微变化，但组间差异均无统计学意义（均P〉0．05）。AL随着近视程度的加深而伸长，ACD随着近视程度的增加而加深，差异均有统计学意义（均P〈0．05）。各组间虹膜厚度（ITl、IT2、IT3）的差异均无统计学意义（均P〉0．05），而房角开放程度指标（TIA与AOD500）、睫状体位置（A角、B角、TCPD、ICPD）、CBT（CBTl、CBT2、CBT3）测量值均随着近视程度的增加而升高，各组间总体比较差异均有统计学意义（均P〈0．05）。AOD500与ACD、睫状体位置（A角）、CBT（CBTl、CBT2）、AL均呈正相关，与屈光度呈负相关，差异均有统计学意义（r=0．573、0．513、0．325、0．398、0．542、-0．435，均P〈O．01）；TIA与ACD、睫状体位置（A角）、CBT（CBTl、CBT2）、AL均呈正相关，与屈光度呈负相关，差异均有统计学意义（r=0．573、0．464、0．276、0．410、0．539、-0．435，均P〈0．01。结论在一定程度上，随着近视屈光度的增加，近视眼ACD加深，房角开放程度增宽，CBT增加，睫状体位置后移。