飞秒激光LASIK术后角膜生物力学各指标和眼压的改变

目的 探讨准分子激光原位角膜磨镶术(laser in situ keratomileusis,LASIK)使用飞秒激光制瓣对近视患者角膜生物力学各指标和眼压的影响.方法 选取111例(222眼)近视患者均行飞秒激光LASIK.分别于术前、术后3个月应用眼反应分析仪检测角膜补偿眼压(corneal compensated intraocular pressure,IOPcc)、模拟Goldmann眼压(Goldmann correlated IOP value,IOPg)、角膜阻力因子(corneal resistance factor,CRF)、角膜滞后量(corneal hysteresis,CH),A型超声测量角膜厚度.比较术后3个月与术前各测量值的差异.结果 术后3个月角膜厚度为(444.00±35.31) μm与术前(536.86±27.09) μm比较,差异有显著统计学意义(t=-55.08,P=0.000),切削深度(92.85±25.12) μm.术后3个月IOPcc、IOPg分别为(14.05±2.32) mmHg(1kPa=7.5 mmHg)、(10.00±2.55) mmHg,较术前(16.03±3.33) mmHg、(14.96±3.32) mmHg显著降低(t分别为-11.111、-24.792,P分别为0.000、0.000).IOPcc、IOPg分别较术前降低(1.98±2.66) mmHg、(4.95±2.98) mmHg. CRF、CH术后测量值(6.54±1.39) mmHg、(7.77±1.23) mmHg较术前(9.90±1.83) mmHg、(9.92±1.62) mmHg显著降低(t分别为-27.976、-21.773,P分别为0.000、0.000).CRF、CH分别较术前降低(3.36±1.79) mmHg、(2.15±1.47) mmHg.角膜切削厚度与CRF、CH改变量呈正相关(r=0.246、0.166,P =0.000、0.013).结论 飞秒激光LASIK术后角膜生物力学各指标和眼压均较术前显著降低,角膜生物力学改变与切削量有关.     

青年女性生理周期期间角膜生物力学性能和眼压的节律性变化

目的探讨中国青年女性生理周期期间角膜生物力学性能和眼压的节律性变化以及两者之间的关系。方法前瞻性研究。41例健康青年女性分别在月经周期初期、排卵期和月经周期末期用眼反应分析仪（ORA）对角膜补偿眼压（IOPcc）、可重复模拟Goldmman眼压（IOPg）、角膜滞后量（CH）和角膜阻力因子（CRF）进行测量。采用Pentacam对CCT进行测量。采用重复测量方差分析法分析测量参数在不同时间点的变化以及Pearson相关进行相关性分析。结果在女性生理周期的不同阶段,CCT、CH和CRF存在波动,但差异无统计学意义,在月经周期末期IOPcc和IOPg均较初期显著下降（P<0.01）。△IOPg与△CRF呈低度正相关（r=0.356,P<0.05）,与△CH呈低度负相关（r=-0.336,P<0.05）,△IOPcc则与△CH呈中度负相关（r=-0.702,P<0.01）,与△CRF不相关（r=-0.069,P>0.05）。△CRF、△CH、△IOPg和△IOPcc均与△CCT无明显相关性（│r│均<0.3,P均>0.05）。结论在女性生理周期期间,角膜生物力学性能无明显变化但眼压在月经周期末期发生了显著下降。IOPg的变化与CH、CRF低度相关,而IOPcc则与CH中度相关,与CRF不相关。角膜生物力学性能可能是眼压的影响因素之一。     

手法小切口白内障摘除术后早期角膜生物力学特性的变化

目的:观察年龄相关性白内障患者手法小切口白内障摘除术(manual small incision cataract surgery,MSICS)后1d角膜滞后性(corneal hysteretic,CH)、角膜阻力因数(cornealresistance factor,CRF)、角膜补偿眼压(corneal compensa-ted IOP,IOPcc)、Goldmann相关眼压(goldmann correlatedIOP,IOPg)的变化规律,并探讨MSICS术后早期角膜生物力学特性改变的相关因素。方法:应用Reichert眼反应分析仪(ocular response analy-zer,ORA)测量50例50眼年龄相关性白内障患者术眼MSICS术前及术后1d的CH,CRF,IOPg,IOPcc。用SPSS10.0统计学软件分析各测量值的变化规律以及CH变化量与眼压变化量的相关性。结果:术后1d的CH,CRF较术前下降(P<0.01;P<0.01),IOPcc,IOPg较术前升高(P<0.01;P=0.001),CH降低量与眼压增加量呈正相关性(IOPg,r=0.492,P<0.01;IOPcc,r=0.688,P<0.01)。结论:年龄相关性白内障患者手法小切口白内障摘除术后早期角膜生物力学特性明显改变,术后角膜不同程度的水肿和眼压的升高可能是导致改变的主要原因。     

飞秒激光LASIK术后角膜生物力学的改变

目的：探讨飞秒激光LASIK术后角膜生物力学指标的改变,为飞秒激光LASIK术的安全性研究提供理论依据。

方法：选取2014-06/2016-06于我院行手术治疗的85例170眼近视患者,所有患者均采用飞秒激光LASIK术治疗,对符合纳入标准的病历资料进行回顾性分析。术前和术后3、6mo采用眼反应分析仪测量角膜补偿眼压(corneal compensated intraocular pressure,IOPcc)、角膜阻力因子(corneal resistance factor,CRF)、角膜滞后量(corneal hysteresis,CH)以及模拟Goldmann眼压(Goldmann correlated IOP value,IOPg),采用A型超声测量仪测量中央角膜厚度。

结果：术后3、6mo中央角膜厚度显著低于术前,差异有统计学意义(P<0.05); 术后3、6mo时IOPcc、CRF、CH、IOPg等角膜生物力学指标均显著低于术前,差异有统计学意义(P<0.05); 术后3、6mo各指标比较,差异无统计学意义(P>0.05); 角膜切削厚度为98.67±7.56μm,CH和CRF变化量分别为3.40±0.34mmHg、3.55±0.43mmHg,角膜切削厚度与CH、CRF变化量呈明显正相关(r=0.232、0.254,P<0.001)。

结论：飞秒激光LASIK术后角膜厚度显著降低,术后各项角膜生物力学指标均显著下降,且3mo后基本趋于稳定。     

眼反应分析仪与非接触眼压计眼压测量的对比观察

目的比较眼反应分析仪(ORA)与非接触眼压计(NCT)测量眼压结果的差异,分析ORA、NCT测量结果与角膜中央厚度(CCT)的关系。方法近视患者57例(114只眼),于准分子激光手术前行ORA测量,得出角膜补偿眼压(IOPcc)和Goldmann相关眼压值(IOPg)两个数值,NCT测眼压3次取平均值。结果 ORA测得IOPcc平均值16.85 mm Hg,IOPpg平均值15.26 mm Hg,NCT眼压计测得平均值15.66 mm Hg;IOPcc>NCT>IOPg。IOPcc、IOPg与NCT所测眼压值比较,差异均有统计学意义(P<0.05)。NCT和IOPg均与CCT呈正相关(r:分别为0.463和0.419,P<0.05);IOPcc与CCT无相关性(r:0.230,P>0.05)。结论 ORA测量屈光不正患者的眼压与NCT测量结果存在一定差异,其中IOPcc不受角膜厚度的影响,在临床运用中准确性较好。     

角膜补偿眼压（IOPcc）和5种眼压校正公式所得校正眼压的一致性及IOPcc、模拟Goldmann眼压与眼球各参数的相关性分析

目的　比较眼反应分析仪测得的角膜补偿眼压（corneal-compensated intraocular pressure,IOPcc）和Sirius眼前节分析系统内置的5种眼压校正公式所得校正眼压的一致性,分析IOPcc、模拟Goldmann眼压（Goldmann-correlated intraocular pressure,IOPg）与眼球各参数的相关性。方法　选取2016年11月至2017年3月在我院眼科中心行近视激光治疗的患者90例90眼,年龄18～37（24.47±5.57）岁。应用Sirius眼前节分析系统对所有患者按常规方法测量3次,选择最佳测量结果作为各参数最终结果。应用眼反应分析仪测量患者的角膜生物力学参数。根据眼反应分析仪测量的IOPg输入Sirius眼前节分析系统内置的5种眼压校正公式进行计算,得到的校正眼压分别记录为Dresdner校正眼压、Ehlers校正眼压、Kohlhaas校正眼压、Orssengo/Pye校正眼压和Shah校正眼压。将所得的5种校正眼压和非接触性眼压计眼压与眼反应分析仪测得的IOPcc进行一致性分析。对IOPcc、IOPg与角膜滞后量、角膜阻力因子、眼球各参数进行相关分析。结果　Kohlhaas校正眼压和IOPcc比较差异有统计学意义（P<0.05）。Dresdner校正眼压、Orssengo/Pye校正眼压与IOPcc的一致性较好,95%一致性界限分别为 （-2.09～2.55）mmHg、（-2.38～2.37）mmHg;其中Dresdner校正眼压与IOPcc的95%一致性界限宽度最窄。IOPcc与角膜滞后量、角膜阻力因子以及眼球各参数均无相关性,而IOPg与角膜阻力因子、中央角膜厚度、角膜体积呈正相关关系 （均为P<0.05）。结论　Dresdner校正眼压、Orssengo/Pye校正眼压与IOPcc的一致性较好;眼球大部分参数对IOPcc影响小。     

SMILE与FS-LASIK术后眼压和角膜生物力学指标的变化比较

目的：比较飞秒激光小切口角膜基质透镜取出术(small incision lenticule extraction,SMILE)、飞秒辅助LASIK术(FS-LASIK)两种手术方式术后眼压和角膜生物力学指标的变化。

方法：选取我院自愿接受SMILE手术101例202眼和FS-LASIK手术101例202眼近视患者,分别于术前、术后1mo应用眼反应分析仪(ocular response analyzer,ORA)检测角膜补偿眼压(corneal compensated intraocular pressure,IOPcc)、模拟Goldmann眼压(Goldmann correlated IOP value,IOPg)、角膜阻力因子(corneal resistance factor,CRF)、角膜滞后量(corneal hysteresis,CH)。比较术后1mo与术前测量值的差异,两组CRF、CH降低值的差异。

结果：术后1mo SMILE组IOPcc、IOPg分别为13.84±2.22、10.81±2.52mmHg,较术前16.15±2.90、15.95±3.08mmHg显著降低(t=-13.58、-32.91,均P<0.01)。CRF、CH术后测量值7.52±1.41、8.66±1.19mmHg较术前10.72±1.61、10.60±1.43mmHg显著降低(t=-41.21、-24.03,均P<0.01)。CRF、CH分别较术前降低3.19±1.10、1.93±1.14mmHg。FS-LASIK组术后1mo IOPcc、IOPg分别为13.99±2.33、10.10±2.55mmHg,较术前15.88±3.29、14.86±3.34mmHg显著降低(t=-10.09、-23.00,均P<0.01)。CRF、CH术后测量值6.68±1.14、7.90±1.27mmHg较术前9.93±1.85、9.98±1.60mmHg显著降低(t=-24.84、-18.90,均P<0.01)。CRF、CH分别较术前降低3.25±1.86、2.08±1.57mmHg。CRF、CH术后降低值SMILE 组显著小于FS-LASIK组(t=-0.351、-1.081,均P<0.01)。

结论：两种手术方式术后角膜生物力学和眼压测量值均较术前显著降低。CRF、CH术后降低值,SMILE 组显著低于FS-LASIK组。     

飞秒激光辅助LASIK术后早期角膜生物力学各指标的变化

目的:探讨准分子激光原位角膜磨镶术(LASIK)使用Femto LDV飞秒激光制瓣近视患者的角膜生物力学各指标的变化。方法:选取93例186眼近视患者均行飞秒激光辅助LASIK术。分别于术前;术后3,6mo应用眼反应分析仪(ocular response analyzer,ORA)检测角膜补偿眼压(corneal compensated intraocular pressure,Iopcc)、模拟Goldmann眼压(Goldmann correlated IOP value,Iopg)、角膜阻力因子(corneal resistance factor,CRF)、角膜滞后量(corneal hysteresis,CH)。超声角膜厚度测量。比较术后3mo与术前,术后6mo与术后3mo测量值的差异。结果:术后3mo中央角膜平均厚度为447.61±39.57μm与术前539.88±29.72μm比较,差异有显著统计学意义(t=-47.223,P=0.000);术后6mo 448.78±39.19μm较术后3mo厚度差异有统计学意义(t=2.15,P=0.033)。术后3mo Iopcc,Iopg分别为13.75±2.13,9.54±2.35mmHg较术前16.29±2.88,15.09±3.29mmHg显著降低(t=-13.604,-23.594;P=0.000,0.000)。Iopcc,Iopg分别较术前降低2.55±2.25,5.55±3.21mmHg。术后6mo 13.61±1.96,9.32±2.07mmHg与术后3mo比较差异无统计学意义(t=-0.977,1.447,P=0.33,0.15)。CRF,CH术后3mo测量值6.36±1.45,7.71±1.30mmHg较术前9.84±1.99,9.77±1.56mmHg显著降低(t=-24.116,-19.171;P=0.000,0.000)。CRF,CH分别较术前降低3.49±1.97,2.06±1.47mmHg。术后6mo 6.24±1.38,7.67±1.25mmHg与术后3mo比较差异无统计学意义(t=1.456,0.636,P=0.147,0.525)。结论:飞秒激光辅助LASIK术对角膜生物力学有显著影响,术后角膜生物力学各指标较术前显著降低。术后3mo内生物力学各指标基本稳定。     

三种眼压计在准分子激光原位角膜磨镶术后的应用比较

目的评价三种不同眼压计在近视准分子激光原位角膜磨镶术后的应用。方法对近视33例66眼和LASIK术后43例86眼分别用非接触眼压计(non—contact tonometer NCT)，Goldmann压平眼压计(Godmann applanalion tonometer，GAT)和Tono-Pen压平眼压计测量眼压(Tono—Pen眼压计测量角膜中央和颞下距角膜缘1．5～2mm处的眼压)，同时测角膜中央及颞下方的厚度。结果用三种方法测得的近视眼LASIK术后的眼压测量值均明显低于正常近视眼。两组均为Tono—Pen和NCT、与GAT测量值呈正相关，LASIK术后中央Tbno—Pen眼压测量值与术前GAT呈正相关。眼压与角膜厚度的关系：近视眼组，NCT与角膜中央厚度呈正相关；GAT和Tono—Pen与角膜厚度无相关性。LASIK术后组，GAT和NCT与角膜厚度呈正相关；Tono-Pen与角膜中央厚度无相关性。结论LASIK术后眼压测量值下降。Tono—Pen测量IOP不受角膜厚度的影响，可应用于LASIK术后等角膜表面不平者。     

角膜生物参数对青光眼患者眼压测量影响的研究

目的:探讨角膜生物参数对青光眼患者眼压测量的影响。方法:对80例121眼青光眼患者进行眼反应分析仪(ocular response analyzer,ORA)与Goldmann压平眼压计(Goldmann applanation tonometer,GAT)测量,并用先进的OrbscanⅡ眼前节分析系统测量中央角膜厚度(central corneal thickness,CCT)。结果:平均矫正眼压(IOPcc)值17.41±5.62mmHg;平均GAT值15.76±6.06mmHg;IOPcc与角膜滞后性(cornealhysteresis,CH)有相关性(P=0.000;r=-0.236);IOPcc与GAT显著相关(P=0.000;r=0.857);IOPcc与CCT无相关性。结论:对已经诊断的青光眼患者,平均IOPcc值高于平均GAT值;随着CH的降低,IOPcc值有升高的趋势;且IOPcc值不受CCT值的影响。     

高度近视眼准分子激光角膜前弹力层下磨镶术前后角膜生物力学变化的研究

目的分析和探讨高度近视患者行准分子激光角膜前弹力层下磨镶术（SBK）前后角膜生物力学特性变化的特点。方法前瞻性系列病例研究。高度近视患者36例（65眼）,年龄19～34岁,平均（22．9±3．6）岁,等效球镜度-6．375—12．50D,平均（-8．35±1．21）D,所有患者均行SBK。术前和术后1个月,应用眼反应分析仪（ORA）对患者的模拟Goldmann眼压（IOPg）、角膜补偿眼压（IOPcc）、角膜阻力因子（CRF）、角膜滞后量（CH）及内向压平时间（Timeln）和外向压平时间（TimeOut）进行测量和分析。应用配对t检验对手术前后IOPg、IOPcc、CRF、CH、Timeln、TimeOut和TimeOut—Timeln变化进行对比分析,采用多重回归和Pearson相关分析影响角膜生物力学特性变化的因素。结果术前IOPg、IOPcc、CRF、CH和TimeIn、TimeOut及TimeOut．Timeln分别为（17．5±3．0）mmHg、（17．6±2．9）mmHg、（11．1±1．4）mmHg、（10．5±1．3）mmHg、（8．0±0．4）ms、（18．6±0．2）ms和（10．7±0．4）ms,术后1个月分别为（12．4±3．5）mmHg、（16．4±3．3）mmHg、（7．0±1．2）mmHg、（7．5±1．0）mmHg、（7．2±O．5）ms、（18．4±0．2）ms和（11．2±0．5）ms。手术前后比较,差异均有显著统计学意义（t=14．2、3．5、28．1、24．9、17．4、16．2、-10．7,P均〈0．01）。aIOPg、aCRF与切削量（AD）呈正相关（r=0．247,P=0．047;r=0．298,P=0．016）,而aIOPcc、aCH和／XTimeln、ATimeOut及a（TimeOut-Timeln）与AD的相关性无统计学意义。结论SBK矫正高度近视会对角膜生物力学产生一定的影响,使其术后角膜生物力学信号发生一系列变化,与激光切削量有一定的相关性。     

Internal limiting membrane dragging and peeling: a modified technique for macular holes closure surgery

AIM: To introduce a modified technique of internal limiting membrane (ILM) centripetal dragging and peeling to treat idiopathic macular hole (IMH) and to observe the ILM-retina adhesive forces. METHODS: Twenty-six consecutive patients with stage 3 to 4 IMH and followed up at least six months were enrolled. All patients underwent complete par plana vitrectomy, ILM dragging and peeling, fluid and gas exchange, 15% C3F8 tamponade and 2-week prone position. The best corrected visual acuity, macular hole evaluation by optical coherence tomography, and complications were evaluated. RESULTS: The mean diameter of IMH was 524±148 μm (range: 201-683 μm), with 21 cases (80.8%) greater than 400 μm. ILM dragging and peeling were successfully performed in all cases. Most of the ILM-retina adhesive forces are severe (42.3%, 11/26), followed by mild (38.5%, 10/26), and moderate (19.2%, 5/26). The mean follow-up duration was 21.2±6.1mo. The IMH was closed in 25 (96.3%) eyes. Visual acuity (logMAR) improved significantly from 1.2±0.6 preoperatively to 0.7±0.5 postoperatively (P<0.001). CONCLUSION: Preexisting ILM-retina adhesive force is found in IMH patients. With assistance of this force, this modified technique may help to release the IMH edges and improve the closure rate of large IMH.     

Changes in corneal biomechanics and intraocular pressure following Femto-LASIK using Goldman applanation tonometry and ocular response analyzer

AIM:To compare intraocular pressure(IOP)measurements before and after laser in situ keratomileusis(LASIK)with a femtosecond laser for flap creation using ocular response analyzer(ORA)and Goldmann applanation tonometry,and to identify factors that may influence the preoperative and postoperative IOP.METHODS:A prospective study conducted on myopic patients who underwent LASIK using a femtosecond laser for flap fashioning.Enrolled patients were evaluated preoperatively,6 wk and 3 mo postoperatively for manifest refraction(MR),keratometric(K)readings and central corneal thickness(CCT)using a scheimpflug-based topography.Corneal resistance factor(CRF),corneal hysteresis(CH),Goldmann correlated IOP(IOPg)and corneal compensated IOP(IOPcc)were measured using ORA besides IOP assessment by Goldman applanation tonometry(GAT).RESULTS:There was a statistically significant decrease in measures of IOPg by 3.35±0.83 mm Hg,followed by GAT which decreased by 2.2±0.44 mm Hg,and the least affected by operation was IOPcc which decreased only by 0.87±0.1 mm Hg after 6 wk.After 3 mo follow up there was a statistically significant decrease in IOPcc which decreased only by 0.76±0.4 mm Hg,followed by IOP GAT by 1.6±0.5 mm Hg,and the most affected by operation was IOPg which decreased by 2.3±0.3 mm Hg.Correspondingly,there was a statistically significant decrease in CH and CRF after 6 wk and 3 mo.At 3 mo,the preoperative MR and preoperative GAT were prominent significant predictors of the postoperative GAT changes.The prediction equation was subsumed.CONCLUSION:IOP measurements and corneal biomechanical factors reduce significantly after LASIK with a femtosecond laser for flap creation.The IOPcc values are less influenced by changes in corneal properties than IOPg and GAT,indicating that IOPcc may provide the most reliable measurement of IOP after this procedure.     

Corneal biomechanical changes and intraocular pressure in patients with thyroid orbitopathy

AIM: To determine the relevance of the objective parameters addressing the altered biomechanical properties of cornea for glaucoma monitoring in patients with mild or moderate thyroid associated orbitopathy (TAO), and in healthy individuals. METHODS: Twenty-five patients with TAO (group 1) and 25 healthy adults (group 2) were included to the study. Both groups were of a similar age and the ratio women:man. For each patient, the following parameters of both eyes were measured with ocular response analyzer (ORA): corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann correlated intraocular pressure (IOPg) and corneal compensated intraocular pressure (IOPcc). In both groups participating in our study, all measurements were performed within minutes to reduce the diurnal effects. RESULTS: The mean age in group 1 was 56±11y and 76% were women, 24% were men. The mean age in group 2 was 64±11y and 68% were women, 32% were men. CH correlated negatively with IOPg in group 1 (r2=0.10, P<0.05). IOPg strongly correlated with IOPcc in both groups (group 1: r2=0.79, P<0.0001; group 2: r2=0.85, P<0.0001). There was positive correlation between CRF and IOPg in group 1 (r2=0.12, P<0.05) and in group 2 (r2=0.31, P<0.0001). Statistical analysis revealed no significant correlation between CRF and IOPcc in group 1 (r2=0.009, P>0.05) and also no significant correlation in group 2 (r2=0.04, P>0.05). CRF mean value in group 2 (11.51±1.72 mm Hg) was higher than in group 1 (10.85±1.45 mm Hg) (P<0.05). IOPg strongly correlated with IOPcc in both groups (group 1: r2=0.79, P<0.0001; group 2: r2=0.85, P<0.0001). There was also strong correlation between CRF and CH in both populations: group 1: (r2=0.58, P<0.0001), group 2: (r2=0.41, P<0.0001). CONCLUSION: Biomechanical parameters of cornea, as quantified by CH and CRF, and measured together with IOPcc, precisely reveal glaucoma staging in TAO and thus are reliable for diagnosing and follow-up in clinical practice.     

近视人群中角膜生物力学特性的分布

目的：分析伊朗近视眼及散光人群中角膜生物力学参数的分布特征。

方法：对接受激光矫正手术的近视眼及散光患者180眼进行前后节、显然验光等效球镜度、Orbscan II和Zywave全面的术前检查。用眼反应分析仪测量角膜滞后量,角膜阻力因子,模拟Goldmann眼压值及角膜补偿后眼压值。分析所有角膜生物力学的分布特性及其与显然验光等效球镜度、性别和年龄的相关性。数据采用SPSS 17软件进行统计学分析,以P<0.05为有显著性差异。

结果：平均年龄为28.20±6.78岁。平均显然验光等效球镜为-4.21±1.19D。平均角膜滞后量,角膜阻力因子,模拟Goldmann眼压值和角膜补偿后眼压值分别为10.00±1.28mmHg,10.17±1.45mmHg,15.71±2.67mmHg和 16.68±2.41mmHg。近视人群中,28.4%角膜滞后量约为10mmHg,71%从9mmHg增长到11mmHg。25.9%的近视人群的角膜阻力因子为10mmHg,48.7%为9mmHg增长到11mmHg。显然验光等效球镜与角膜滞后量(Rs=0.001,P=0.71)和显然验光等效球镜与角膜阻力因子(Rs=0.01,P=0.18)之间正相关性不明显。

结论：研究显示了伊朗近视眼人群中角膜生物力学的分布特征(角膜滞后量,角膜阻力因子,模拟Goldmann眼压值及角膜补偿后眼压值),并证实了角膜生物力学特性参数和显然验光等效球镜,年龄及性别之间没有统计学相关性。     

Effect of biometric characteristics on biomechanical properties of the cornea in cataract patient

AIM: To determine the impact of biometric characteristics on the biomechanical properties of the human cornea using the ocular response analyzer (ORA) and standard comprehensive ophthalmic examinations before and after standard phacoemulsification. METHODS: This study comprised 54 eyes with cataract with significant lens opacification in stages I or II that underwent phacoemulsification (2.8 mm incision). Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated intraocular pressure (IOPcc) were measured by ORA preoperatively and at 1mo postoperatively. Biometric characteristics were derived from corneal topography [TMS-5, anterior equivalent (EQTMS) and cylindric (CYLTMS) power], corneal tomography [Casia, anterior and posterior equivalent (EQaCASIC, EQpCASIA) and cylindric (CYLaCASIA, CYLpCASIA) power], keratometry [IOLMaster, anterior equivalent (EQIOL) and cylindric (CYLIOL) power] and autorefractor [anterior equivalent (EQAR)]. Results from ORA were analyzed and correlated with those from all other examinations taken at the same time point. RESULTS: Preoperatively, CH correlated with EQpCASIA and CYLpCASIA only (P=0.001, P=0.002). Postoperatively, IOPg and IOPcc correlated with all equivalent powers (EQTMS, EQIOL, EQAR, EQaCASIA and EQpCASIA) (P=0.001, P=0.007, P=0.001, P=0.015, P=0.03 for IOPg and P<0.001, P=0.003, P<0.001, P=0.009, P=0.014 for IOPcc). CH correlated postoperatively with EQaCASIA and EQpCASIC only (P=0.021, P=0.022). CONCLUSION: Biometric characteristics may significantly affect biomechanical properties of the cornea in terms of CH, IOPcc and IOPg before, but even more after cataract surgery.     

Corneal biomechanical properties changes after coaxial 2.2-mm microincision and standard 3.0-mm phacoemulsification

AIM: To compare the changes in corneal biomechanics measured by ocular response analyzer (ORA) after 2.2-mm microincision cataract surgery and 3.0-mm standard coaxial phacoemulsification. METHODS: The prospective nonrandomized study comprised eyes with cataract that had 2.2-mm coaxial microincision or 3.0-mm standard incision phacoemulsification. The corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPcc) and Goldmann-correlated intraocular pressure (IOPg) were measured by ORA preoperatively and at 1d, 1-, 2-, 3- and 4-week postoperatively. Results were analyzed and compared between groups. RESULTS: In both groups, CH decreased in the immediate postoperative period (P<0.05), returned to the preoperative level at one week (P=0.249) in the 2.2-mm group, and at two weeks in the 3.0-mm group (P=0.264); there was no significant change in CRF values. In 2.2-mm group, mean IOPcc and IOPg increased at 1d postoperatively (both P<0.05), and returned to preoperative level at one week (P=0.491 and P=0.923, respectively). In 3.0-mm group, mean IOPcc and IOPg increased at 1d and 1wk postoperatively (P=0.005 and P=0.029, respectively), and returned to preoperative level at 2wk (P=0.347 and P=0.887, respectively). CONCLUSION: Significant differences between preoperative and postoperative corneal biomechanical values were found for CH, IOPcc and IOPg. But the recovery time courses were different between the two groups. The 2.2-mm coaxial microincision cataract surgery group seemed recovery faster compared to the 3.0-mm standard coaxial phacoemulsification group.     

Influence of corneal astigmatism, corneal curvature and meridional differences on corneal hysteresis and corneal resistance factor

Background: This study investigated the influence of corneal astigmatism, corneal curvature and meridional differences on corneal hysteresis (CH) and the corneal resistance factor (CRF) in a group of normal Chinese persons. Methods: Ninety‐five participants were recruited and data from the eye with higher corneal astigmatism were analysed. The anterior corneal curvature was measured by corneal topography. The Goldmann‐correlated intraocular pressure (IOPg), corneal‐compensated intraocular pressure (IOPcc), CH and CRF at different meridians (default horizontal position, 10°, 20° and 30° along the superotemporal and inferonasal meridians) were obtained from an ocular response analyser. The corneal powers at these specific meridians also were calculated. Results: At the default position, the IOPg and CRF had weak correlations with corneal astigmatism, while the IOPcc and CH were not significantly correlated with corneal astigmatism. Both the IOPg and IOPcc were measured significantly higher at the default position. The CH and CRF were lower at the default position but the difference in the CRF from obliquity could not reach statistical significance. The CH was not significantly correlated with the corneal power at all meridians. The CRF correlated with the corneal power only at 30° superotemporal. Conclusion: Corneal astigmatism and head tilt did not have much effect on the measurement of CH and the CRF, both of which were lowest along the horizontal meridian. Clinically, the difference was small. The influence of corneal power on CH and the CRF was minimal.