LASIK术后角膜生物力学变化与眼压测量值的相关性

目的 观察LASIK术后角膜生物力学参数和眼压测量值的变化及角膜生物力学变化与眼压的相关性。设计 前瞻性病例系列。研究对象 哈尔滨医科大学附属第一医院2014年1-12月LASIK手术患者81例（162眼）。方法 应用非接触眼压计（non-contact tonometer,NCT）分别在术前及术后3个月测量眼压。同时应用眼反应分析仪（ocular response analyzer,ORA）测量角膜滞后量（corneal hysteresis,CH）、角膜阻力因子（corneal resistance factor, CRF）、模拟Goldmann 眼压（Goldmann intraocular pressure,IOPg）和角膜补偿眼压（corneal-compensated intraocular pressure,IOPcc）。比较手术前后各参数的变化并分析术后角膜生物力学参数变化与眼压测量值的相关性。 主要指标 手术前后NCT、IOPcc、IOPg、CH、CRF。 结果 LASIK术后3个月CH、CRF、IOPcc、IOPg、NCT测量值与术前比较均显著降低,术后IOPcc与IOPg和NCT之间比较差异均有统计学意义（P<0.05）;△CH、△CRF与△IOPcc、△IOPcc- IOPg和△IOPcc-△NCT均成负相关,△CH、△CRF与△IOPg和△NCT均成正相关（P<0.05）;CH和CRF的减少量与眼压测量值下降具有相关性（P<0.05）。结论 LASIK术后角膜生物力学参数和眼压测量值均较术前显著降低,眼压测量值下降与CH和CRF的减少量具有相关性,说明眼压下降的程度可能受角膜生物力学特性的影响。     

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。     

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.     

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。     

角膜补偿眼压与前房穿刺测量眼内压的比较

目的 比较角膜补偿眼压(IOPcc)与前房穿刺测量眼压(direct intracameral IOP,IOPintra),探讨角膜生物特性对眼压测量的影响.方法 双肓前瞻性研究.拟行超声乳化手术患者73例(73只眼),随机选择1只眼.超声测厚仪测量中央角膜厚度(CCT),ORA测量IOPcc和角膜生物属性:角膜滞后性(cornealhysteresis,CH).角膜阻力因子(corneal resistance factor,CRF).应用IOD眼压测量装置行前房穿刺测量IOPintra.结果 IOPintra为(15.48±4.64)mmHg,IOPcc为(16.63±3.68)mmHg;IOPcc高出IOPintra(1.15±4.12)mmHg(P=0.019);IOPcc和IOPintra与CH、CRF相关,IOPcc,IOPintra及两者的差异与CCT不相关;IOPcc与IOPintra的差异与cH相关(r=-0.283 P=0.015).结论 IOPcc读数比IOPintra高1.15mmHg,其差异受CH影响.角膜生物属性对眼压测量的影响需慎重考虑.     

FS-LASIK联合胶原交联术后的早期临床观察

目的：探讨飞秒激光辅助准分子激光原位角膜磨镶术(femtosecond laser-assisted excimer laser in situ keratomileusis,FS-LASIK)联合胶原交联术后的早期安全性和有效性。

方法：选取2016-07/2017-08我院接受飞秒辅助LASIK联合胶原交联术近视患者30例60眼,分别于术前、术后1、3mo检查裸眼视力。应用角膜地形图(TMS)测量陡峭K值(Ks)、平坦K值(Kf)、角膜规则指数(SRI)、角膜非对称指数(SAI)。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)。伽利略眼前节分析值包括前后表面屈光度和角膜厚度分布。角膜内皮细胞计数仪器进行内皮计数检查,比较手术前后各指标的差异。

结果：术后1d 26眼(43%)、1mo 55眼(92%)、3mo 50眼(83%)裸眼视力保持0.8以上。术后1mo与术前比较,IOPcc、IOPg、CRF、CH较术前显著降低,差异均有统计学意义(P<0.01)。术后3mo与1mo比较,IOPcc、IOPg、CRF、CH值无统计学差异(P>0.05)。角膜地形图参数：术后1mo与术前比较,Ks、Kf显著下降(P<0.01),SRI、SAI显著上升(P<0.01); 术后3mo与1mo比较,Ks有显著升高(P<0.05),Kf变化无统计学差异(P>0.05),SRI、SAI有显著下降(P<0.05)。伽利略眼前节分析中：模拟角膜曲率计陡峭K值(Sim Ks)、模拟角膜曲率计平坦K值(Sim Kf)在3mo较1mo有0.94D和0.95D的增长。另外,前后表面Kf值3mo较1mo明显增加,差异有统计学意义(P<0.01); 而Ks值差异无统计学意义(P>0.05)。同时,中心点、厚度最薄点,术后3mo与1mo角膜厚度差异无统计学意义(P>0.05)。角膜内皮计数检查：术前(3059.95±247.87/mm²)与术后1mo(3052.87±267.71/mm²)比较,差异无统计学意义(t=0.279,P>0.05)。

结论：屈光角膜手术联合胶原交联术对于度数高和角膜薄、角膜厚度分布不均、地形图异常(除外圆锥角膜)的患者治疗安全有效。     

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。     

近视LASIK术后角膜生物力学参数变化的相关性

目的:观察近视LASIK术后角膜生物力学参数与形态参数变化的相关性。方法:近视患者69例136眼,于LASIK术前及术后1mo行眼反应分析仪(ORA)测量角膜滞后(CH)和角膜阻力因子(CRF),Pentacam眼前节分析仪测量眼前节参数。计算术后角膜生物力学参数变化ΔCH及ΔCRF,Pentacam测量角膜中央厚度变化ΔCCT,中央2,4,6mm平均角膜厚度变化(ΔCCT2mm,ΔCCT4mm和ΔCCT6mm),角膜容积变化ΔCV,角膜前后表面曲率半径变化ΔRa和ΔRp,分析ΔCH和ΔCRF与角膜形态参数的相关性。结果:LASIK术前平均CH及CRF(9.99±1.38和9.96±1.30mmHg)明显高于术后1moCH和CRF(7.90±1.16和6.49±1.28mmHg),差异具有统计学意义(P<0.05)。LASIK术后ΔCH和ΔCRF与ΔRp和ΔCCT6mm无相关性,ΔCH和ΔCRF与ΔCCT,ΔCCT2mm,ΔCCT4mm和ΔCV呈正相关(r:0.513,0.397,0.329和0.314,P<0.05;r:0.616,0.504,0.484和0.466,P<0.01);ΔCRF与ΔRa呈负相关(r:-0.374,P<0.01)。结论:近视LASIK术后角膜CH和CRF变化与角膜厚度及容积有关,CRF评价LASIK术后角膜生物力学变化比CH更有价值。     

Influence of preoperative astigmatism on corneal biomechanics and accurate intraocular pressure measurement after micro-incision phacoemulsification

AIM: To define the corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg) and corneal compensated intraocular pressure (IOPcc) prior to and following coaxial micro-incision phacoemulsification in patients with corneal astigmatism. METHODS: Of 97 patients with cataracts were enrolled in the study. Group 1 included patients with corneal astigmatism (K1-K2) values of K1-K2<+1.0 D, and group 2 with values of K1-K2 ≥+1.0 D and ≤+2.25 D. Coaxial micro-incision phacoemulsification of a corneal incision of 2.0 mm with intraocular lens (IOL) implantation was performed. CH, CRF, IOPg, IOPcc, waveform score (WS) were measured preoperatively and one week, one month postoperatively using an Ocular Response Analyzer. Axial length (AXL) was calculated by Tomey Optical Biometer OA 2000. RESULTS: Group 1 consisted of 51 patients with mean corneal astigmatism value of +0.49±0.25 D. Group 2 included 46 patients with astigmatism of +1.43±0.43 D. In group 1, CRF (t=2.68, P<0.05), CH (t=2.64, P<0.05) and WS (t=3.51, P<0.05) were significantly lower one week postoperatively, when compared to the preoperative values. CRF significantly decreased (t=3.61, P<0.05) when measured one month following the surgery. In group 2 CH (t=5.92, P<0.05), and WS (t=3.96, P<0.05) were significantly lowered one week after cataract surgery. Moreover, we observed a significant decrease in IOPg (t=2.24, P<0.05), CRF (t=5.05, P<0.05) and CH (t=2.31, P<0.05) one month after phacoemulsification. There was no statistically significant (t=-0.83, P=0.41) difference in AXL between study groups. CONCLUSION: CRF, CH and IOPg are reduced in patients with preoperative corneal astigmatism equal or higher than +1.0 D and lower than +2.25 D. Hence, bias of IOPg measurement in these patients may cause underestimation of the real IOP both before and after cataract surgery. The measurement of IOPcc allows the precise assessment of IOP pre- and postoperatively, independently on corneal astigmatism, CH and CRF values.     

Repeatability of intraocular pressure and corneal biomechanical properties measurements by the ocular response analyser

BACKGROUND: The Ocular Response Analyser (ORA, Reichert Ophthalmic Instruments) is a non-contact applanation tonometer, providing two measures of intraocular pressure (IOP) - IOPg which represents a Goldmann equivalent IOP measure and IOPcc, representing a measure of IOP independent of corneal effects. In addition, the device provides two measures believed to represent corneal biomechanical properties: corneal hysteresis (CH) and corneal resistance factor (CRF). The aim of this study was to assess the repeatability of these measurements. PATIENTS AND METHODS: One randomly chosen eye from 49 healthy volunteers was measured four times consecutively with the ORA prior to Goldmann applanation tonometry (GAT). The repeatability coefficient (RC), the coefficient of variation (CV) and the intraclass correlation coefficient (ICC) were calculated as a measure of intrasession repeatability. RESULTS: CH was the most variable and IOPg the most repeatable measure, with an RC of 2.61 and 1.97, respectively, and ICC of 0.86 and 0.92, respectively. CV ranged between 5.73 % for IOPg and 12.38 % for CH. ORA IOP measurements were higher than GAT (IOPcc = 17.43 +/- 3.23; IOPg = 17.53 +/- 3.0; GAT = 15.75 +/- 2.77 mmHg). CONCLUSIONS: ORA measurements show good short-term repeatability in normal volunteers. Thus, this device appears to be applicable in clinical practice.     

Corneal biomechanical properties in normal‐tension glaucoma

Purpose: To investigate the intraocular pressure (IOP) and corneal biomechanical properties of normal and normal‐tension glaucoma (NTG) eyes. Methods: This study included 83 normal and 83 NTG eyes. We measured corneal‐compensated IOP (IOPcc), Goldmann‐correlated IOP (IOPg), corneal resistance factor (CRF), corneal hysteresis (CH) and central corneal thickness (CCT) three times each for normal and NTG eyes using an Ocular Response Analyzer (ORA). Results: No significant difference in CCT was seen between normal eyes (541.4 ± 26.8 μm) and NTG eyes (535.4 ± 24.9 μm; p = 0.16). IOPcc was significantly higher in NTG eyes (16.1 ± 2.6 mmHg) than in normal eyes (15.1 ± 2.9 mmHg; p = 0.01), while IOPg was significantly lower in NTG eyes (14.1 ± 2.7 mmHg) than in normal eyes (15.1 ± 3.0 mmHg; p = 0.04). CRF and CH were significantly lower in NTG eyes (CRF, 8.9 ± 1.5 mmHg; CH, 9.2 ± 1.3 mmHg) than in normal eyes (CRF, 10.6 ± 1.4 mmHg; CH, 10.8 ± 1.3 mmHg; p < 0.0001 each). Conclusion: IOPcc was significantly higher in NTG eyes than in normal eyes. The ORA may be useful for distinguishing between the IOPcc of NTG eyes with normal IOP and that of normal eyes. In addition, the ORA enables CRF and CH to be measured in vivo, and weakness of the lamina cribrosa may be clinically inferred from the fact that CRF and CH were reduced in NTG eyes in our study. Low CRF and CH may be clues to the pathology of NTG.     

Ocular Response Analyzer in subjects with and without glaucoma.

PURPOSE: The Ocular Response Analyzer (ORA) is a newly introduced tonometer that uniquely measures and then integrates corneal biomechanical data into its intraocular pressure (IOP) estimates in an effort to improve accuracy of IOP assessment. This study was devised to investigate whether ORA-derived IOP and corneal biomechanical variables might be useful in discriminating between subjects with and without primary open-angle glaucoma (GLC). METHODS: All patients seen in the Albuquerque VAMC eye clinic over a 10-week period who demonstrated acceptable ORA signal profiles were retrospectively identified. In subjects classified as normal (NML), ocular hypertension (OH), glaucoma suspect (GS), and GLC, the following variables were compared: age, ethnicity, Goldmann IOP, central corneal thickness (CCT), and ORA-derived data: Goldmann-correlated IOP (IOPg), corneal-compensated IOP (IOPcc), corneal resistance factor (CRF), corneal hysteresis (CH), and difference between IOPcc and IOPg (DIOP; IOPcc - IOPg). RESULTS: Right eyes in 71 NML, 58 OH, 70 GS, and 99 GLC subjects were studied. Using analysis of variance, higher mean age, higher mean DIOP, and lower mean CH were found in the GLC group compared with OH, GS, and NML groups. In multivariate regression analyses, factors that independently discriminated between groups were: age, IOPcc, and DIOP (GLC vs. NML); age and IOPcc (GLC vs. GS); age and CRF (GLC vs. OH). When DIOP was left out of the models, CH replaced DIOP in the GLC vs. NML analysis with nearly equal statistical power. CONCLUSIONS: Our results suggest that ORA-generated parameters may be useful for differentiating subjects with and without GLC. Furthermore, the discriminatory power of each ORA variable seems to depend on the diagnostic groups that are being compared. Finally, our findings also suggest that measured IOP may be significantly underestimated in glaucoma patients compared with non-glaucoma patients.     

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.     

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.     

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.     

Effect of pathological myopia on biomechanical properties: a study by ocular response analyzer

AIM: To evaluate the ocular response analyzer (ORA) measurements of patients with pathological myopia in comparison with those of emmetropic control subjects, and to investigate the correlation between these ORA measurements and spherical equivalent (SE). METHODS: Measurements of 53 eyes of 53 subjects with pathological myopia (SE>-6.00 D) were compared with those of 60 eyes of 60 emmetropic controls. Corneal hysteresis (CH), corneal resistance factor (CRF), noncontact tonometer intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) were obtained for each subject. The refractive error value was determined as SE via a cycloplegic refraction test. RESULTS: The mean age was 54.1±18.9y (ranging from 5 to 88) in the pathological myopic group and 56.2±19.0y (ranging from 6 to 89) in the control group. There were no significant differences between the groups concerning age and sex. CH and CRF were significantly lower in the pathological myopic group than in the control group (P<0.001, P=0.005, respectively). IOPcc and IOPg were significantly higher in the pathological myopic group than in the control group (P<0.001, P=0.009, respectively). There were significantly positive correlations between CH and SE (r=0.565, P<0.001) and between CRF and SE (r=0.364, P=0.007). There were significantly negative correlations between IOPcc and SE (r=-0.432, P=0.001) and between IOPg and SE (r=-0.401, P=0.003). CONCLUSION: The present study displayed that pathological myopia affected biomechanical properties measured by ORA. The results of corneal biomechanical properties measured by ORA may need to be appreciated by taking refraction into account. Further, pathological myopia might be related with the increased IOP.     

Reproducibility of viscoelastic property and intraocular pressure measurements obtained with the Ocular Response Analyzer

Purpose: To analyse the reproducibility of corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann‐correlated intraocular pressure (IOPg) and corneal‐compensated intraocular pressure (IOPcc) obtained with the ocular response analyzer (ORA). Methods: This is a prospective study, nonmasked, of eight successive examinations with the ORA device in 60 normal eyes. Using 30 eyes (one eye per subject), the reproducibility was assessed by comparing the first series of four examinations to the second four and by calculating the within‐subject coefficient of variation. The correlation and difference with the fellow eye were analysed, respectively. Results: The mean values were 10.7 ± 1.8 mmHg, CRF; 10.6 ± 1.6 mmHg, CH; 15.9 ± 3.9 mmHg, IOPg and 16.2 ± 3.7 mmHg, IOPcc. The reproducibility was significantly different for CRF (5.2 ± 5.9%), CH (7.3 ± 8.6%), IOPg (7.7 ± 6.7%) and IOPcc (10.1 ± 8.0%); p < 0.001. Considering the reproducibility, CRF correlated with CH (rs = 0.55; p < 0.001) and showed to be independent of IOPg and IOPcc. The score spread was best for CRF (2.6 ± 1.5 mmHg; 24.0%) compared to IOPg (4.3 ± 1.5 mmHg; 28.1%) and CH (3.1 ± 1.7 mmHg; 29.9%) and worst for IOPcc (5.5 ± 2.5 mmHg; 34.4%). The lowest difference with the fellow eye was observed for CRF (5.0%; p = 0.09). The correlation with the fellow eye was high, especially for IOPcc and CRF (rs > 0.9; p < 0.001) followed by IOPg and CH (rs > 0.8; p < 0.001). Conclusion: The ORA device provides reproducible information on viscoelastic properties of the cornea in normal eyes notably CRF and CH. IOPcc was less reproducible. Four measurements per eye were necessary to reach a 10% precision and six for 5%.     

Impact of dehydration and fasting on intraocular pressure and corneal biomechanics measured by the Ocular Response Analyzer

Purpose

To investigate the effects of dehydration and fasting on the intraocular pressure (IOP) and corneal biomechanics during Ramadan in healthy subjects.

Methods

A total of 36 healthy fasting male volunteers with a mean age of 32.7 ± 5.1 years (range 28–38 years) were enrolled in the study. A Reichert Ocular Response Analyzer (ORA) was used to measure the corneal resistance factor (CRF), corneal hysteresis (CH), Goldman-correlated IOP (IOPg), and corneal-compensated IOP (IOPcc), additionally IOP with Goldmann applanation tonometer (IOP-GAT) was taken. All measurements were recorded at 8:00 am and 4:00 p.m. during Ramadan and during a 1-month follow-up after Ramadan was over.

Results

Statistical analysis demonstrated no difference in the ORA measurements including CH, CRF, IOPcc, and IOPg; CCT and CV values between fasting and non-fasting periods or within a single day (diurnal changes). Nine volunteers (25% of total subjects) were excluded because eyedrops were believed to disrupt the Ramadan fast consequently IOP-GAT could not be measured from these subjects. No statistically significant difference was noted between IOP-GAT and IOPg measurements of twenty-seven subjects at the different periods and time points.

Conclusions

Our results reveal that fasting during Ramadan does not profoundly affect corneal biomechanics and IOP values in healthy volunteers without ocular diseases such as glaucoma. When planning corneal refractive surgery and determining IOP, the ORA measurements can be done safely during a Ramadan fast. Moreover, ORA may be a better alternative for patients that refuse IOP measurement via GAT for examining the accuracy of IOP during fasting. Further studies are needed to better understand the role of these parameters on corneal disease and glaucoma during fasting.