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.     

Corneal biomechanics measured with the ocular response analyser in patients with unilateral open‐angle glaucoma

Purpose: To evaluate the relationship between biomechanical properties of the cornea and intraocular pressure (IOP) and the role of biomechanical properties in eyes of patients with unilateral primary open‐angle glaucoma (POAG). Methods: The biomechanical properties of corneal hysteresis (CH) and the corneal resistance factor (CRF) were measured with the ocular response analyser (ORA). In an experimental setting, three human donor eyes with Schiotz‐tonometry‐controlled IOP were investigated. In addition, a series of patients with unilateral POAG were evaluated. Main outcome measures were CH, CRF, corneal‐compensated IOP (IOPcc), standard automated perimetry parameters mean defect (MD) and pattern standard deviation, central corneal thickness, Goldmann applanation tonometry (GAT), and cup‐to‐disc ratio. Results: A highly significant linear correlation between CH and the corneal‐compensated IOP (IOPcc, r = ?0.926; p < 0.001) was found. The correlation between IOP_CC and CRF was not significant (r = 0.335; p = 0.08). In total, 36 eyes of 18 patients with unilateral POAG were examined. Regarding uncorrected CH (mean 7.73 ± 1.46 mmHg glaucomatous eye and 9.28 ± 1.42 mmHg fellow eye), there was a highly significant difference between both eyes. This difference disappears, when CH was corrected for IOP (9.44 ± 3.78 mmHg and 9.97 ± 3.22 mmHg, respectively). Conclusions: Corneal hysteresis but not corneal resistance factor is dependent on IOP. In patients with unilateral POAG, IOP is higher in the affected eye. When CH is corrected for IOP, corneal biomechanical properties do not differ in both eyes of patients with unilateral POAG.     

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。     

Relationship Between Corneal Hysteresis and Corneal Resistance Factor with Other Ocular Parameters

Abstract

Purpose: To evaluate the relationship between corneal hysteresis (CH) and corneal resistance factor (CRF) with age, central corneal thickness (CCT), corneal curvature (KM), corneal volume (CV), and refractive error in naïve eyes. Methods: 105 healthy subjects (58 male and 47 female) were included in this study. The ages ranged from 19 to 82 years (mean 43.1?±?15.4 years) and refraction between ?11?D and +6?D (mean ?0.79?±?2.95?D). CH and CRF obtained with the Ocular Response Analyzer (ORA) were correlated with age, refractive error, Goldmann Applanation Tonometry (GAT), and with CCT, KM, CV obtained with the Pentacam, and with Corneal-Compensated Intraocular Pressure (IOPcc) and Goldmann-correlated intraocular pressure measurement (IOPg) obtained with ORA. A multivariable mixed effect model was used to evaluate associations among these parameters. Results: CH ranged from 6.9 to 14.6?mmHg (mean 10.26?±?1.49?mmHg); CRF ranged from 5.8 to 17?mmHg (mean 10.38?±?1.64?mmHg). Multivariate analysis showed a statistically significant correlation between CH with CCT (p?<?0.001), and KM (p?<?0.001), and between CRF with CCT (p?<?0.001) and GAT (p?<?0.001). Conclusions: Our findings support the hypothesis that CH and CRF are related to the corneal shape and thickness, and show a decrease of CH with age.     

Corneal biochemical features of patients with vernal keratoconjunctivitis

Background

Vernal keratoconjunctivitis (VKC) is a chronic, bilateral, seasonally exacerbated, allergic inflammation of the ocular surface, involving bulbar and ? or tarsal conjunctiva and cornea. The ocular response analyzer (ORA) measures corneal biomechanical properties in vivo by monitoring and analyzing the corneal behavior when its structure is submitted to a force induced by an air jet. This study was designed to examine corneal biomechanical properties and intraocular pressure in patients with VKC, and to compare with control eyes.

Methods

ORA measurements were performed on the both eyes of 26 patients with VKC (group I) and 14 healthy children who served as the control group (group II). Corneal hysteresis (CH), corneal resistance factor (CRF) and intraocular pressure [Goldmann correlated (IOPg) and corneal compensated (IOPcc)] were recorded with ORA.

Results

Mean age of patients with VKC and control groups were 11.3?±?5.8 and 10.6?±?1.9 years for groups I and II respectively. Mean (± SD) of the CH and CRF readings were 10.1?±?1.6 versus 10.5 ±1.6 (p?>?0.05) and 9.5?±?1.7 versus 10.8?±?1.7 mmHg (p?<?0.05), in groups I and II respectively. Mean (± SD) of the IOPg and IOPcc recordings were 13.3 ±3.4 versus 16.6 ±3.6 mmHg (p?<?0.05) and 14.3?±?3.4 versus 16.9?±?3.7 mmHg (p?>?0.05) in groups I and II respectively. Statistical analysis revealed significant differences for CRF and IOPg between the study groups.

Conclusion

The mean CRF and IOPg values of patients with VKC were lower than those of controls. According to the results of our study, one can conclude that corneal biomechanical property, CRF, could be different in VKC patients compared to normals.     

Are There Any Changes in Corneal Biomechanics and Central Corneal Thickness in Fuchs’ Uveitis?

Purpose: To compare corneal biomechanics, intraocular pressure (IOP) and central corneal thickness (CCT) of 38 patients with unilateral Fuchs’ uveitis (FU) with 42 healthy controls.

Methods: Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated and corneal-compensated IOP (IOPg and IOPcc, respectively) and CCT were measured.

Results: The mean CH, CRF, and IOPg of the involved FU eyes were significantly lower (9.5?±?1.6, 9.0?±?1.9 and 13.1?±?4.3?mmHg) than contralateral eyes (10.1?±?1.7, 9.9?±?1.7 and 14.6?±?3.4?mmHg), and controls (10.5?±?1.5, 10.3?±?1.5 and 14.8?±?2.5?mmHg), respectively. There was no significant difference for mean IOPcc between involved FU or contralateral eyes and controls (14.8?±?4.1, 15.5?±?3.4 and 15.0?±?2.7?mmHg). The CCT values correlated with CH and CRF in the involved and contralateral eyes.

Conclusions: Involved FU eyes had lower CH, CRF, and IOPg than contralateral eyes and controls, with no difference regarding IOPcc.     

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.     

Corneal Biomechanical Characteristics in Patıents with Behçet Disease

Aim: To examine corneal biomechanical properties, intraocular pressure, and central corneal thickness in uveitic eyes with Behçet disease (BD) and to compare them with healthy controls. Methods: This study included 40 eyes of 34 patients with ocular BD and 20 eyes of 20 healthy controls. Eyes with ocular BD were subdivided into active and inactive groups. Ocular response analyzer (ORA) measurements were performed on the 20 eyes of 16 patients with active BD (group 1), 20 eyes of 18 patients with inactive BD (group 2), and 20 eyes of 20 healthy volunteers who served as the control group (group 3). Corneal hysteresis (CH), corneal resistance factor (CRF), intraocular pressure (Goldmann correlated [IOPg], and corneal compensated [IOPcc]) and central corneal thickness (CCT) values were recorded. Results: Mean age of patients in groups 1, 2, and 3 was 33.81?±?9.36, 32.38?±?9.08, and 31.05?±?5.85 years, respectively (p?=?0.76). Mean CH, CRF, IOPg, IOPcc, and CCT values in groups 1, 2, and 3 were [8.51?±?1.88, 9.72?±?2.11, 19.87?±?2.92, 16.13?±?3.29, and 592.50?±?39.95], [8.46?±?1.82, 8.45?±?1.98, 15.89?±?2.68, 15.35?±?2.91, and 528.35?±?19.18], and [8.47?±?1.48, 8.43?±?1.58, 15.59?±?2.74, 15.42?±?3.19, and 526.30?±?18.21], respectively [(p₁?=?0.040, 0.904, <0.001, 0.495 and <0.001 for CRF, CH, IOPg, IOPcc and CCT in group 1, respectively), (p₂?=?0.989, 0.904, 0.659, 0.989, and 0.989 for CRF, CH, IOPg, IOPcc and CCT in group 2, respectively), (p₃?=?0.989, 0.904, 0.660, 0.989, and 0.989 for CRF, CH, IOPg, IOPcc and CCT in group 3, respectively)]. Conclusion: CRF, IOPg, and CCT values altered in active BD group when compared with inactive BD and control group (p?相似文献   

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。     

Age-related change in corneal biomechanical parameters in a healthy Caucasian population

Purpose: To determine the effect of aging on corneal biomechanical parameters measured via ocular response analyzer in a homogenous healthy Caucasian population.

Methods: A total of 2039 Caucasian adults were consecutively recruited and divided into seven groups according to decades of age. The difference in mean corneal hysteresis (CH), mean corneal resistance factor (CRF), mean Goldmann-correlated intraocular pressure (IOPg), and mean corneal-compensated IOP (IOPcc) between decades of age were investigated. The strength of the correlations between corneal biomechanical parameters, and between each biomechanical parameter and age were evaluated. The effect of age on each corneal biomechanical parameter was analyzed.

Results: Mean age of the participants (1173 female and 866 male) was 43.30 ± 14.64 years. Mean CH, CRF, IOPcc, and IOPg were 11.49 ± 1.89 mmHg, 11.40 ± 2.30 mmHg, 15.01 ± 3.11 mmHg, and 15.72 ± 3.80 mmHg, respectively. There were significant differences in mean CH, CRF, IOPcc, and IOPg between groups (p < 0.001 for all parameters). There was a significant negative correlation between age and CH (r = –0.067 and p = 0.003), and a significant negative correlation between age and CRF (r = –0.053 and p = 0.017). There was a significant positive correlation between age and IOPg (r = 0.25 and p < 0.001), and between age and IOPcc (r = 0.20 and p < 0.001). Linear regression analysis showed that for every 1-year increase CH decreased 0.011 mmHg, CRF decreased 0.004 mmHg, IOPcc increased 0.053 mmHg, and IOPg increased 0.047 mmHg.

Conclusions: Aging can cause significant changes in corneal biomechanical parameters. Corneal biomechanical parameters were correlated with each other, and each was correlated with aging.     

Ocular response analyser measurements and central corneal thickness in ocular rosacea patients

Rosacea is a chronic cutaneous disorder which is known to cause inflammation and increased proteolytic activity on the ocular surface that might lead to corneal biomechanical alterations. The aim of this study is to evaluate the corneal biomechanical properties of ocular rosacea patients and compare the measurements with healthy individuals as measured with Reichert ocular response analyser (ORA). Besides full eye examination [best corrected visual acuity (BCVA), intraocular pressure (IOP) measured with Goldmann applanation tonometry (IOP-G)], central corneal thickness (CCT), and ORA [corneal hysteresis (CH), corneal resistance factor (CRF), corneal compensated IOP (IOPcc), Goldmann correlated IOP (IOPg)] measurements of 30 eyes of 15 ocular rosacea patients (study group) and 30 eyes of 15 healthy individuals (control group) were performed. For comparisons paired t test was used. Mean age of study group was 45.26 ± 11.65 (range 25 and 63) and control group was 45.00 ± 8.91 (range 26 and 58) years (p = 0.865). No significant difference in BCVA, CCT, IOP-G, IOPcc was detected among groups. However, IOPg, CH, and CRF in the study group were significantly lower than in the control group (p = 0.013, p = 0.013, p = 0.009, respectively). IOPg, CH, and CRF parameters of ocular rosacea patients were significantly lower than normal individuals. These differences and their probable clinical reflections that might effect making decisions in conditions such as glaucoma should be investigated in larger number of patients.     

Corneal biomechanical characteristics in children with diabetes mellitus

To compare the corneal biomechanical properties in children with type 1 diabetes mellitus (DM) and healthy children. In this cross-sectional study, the study and control groups were composed of 68 children with DM and 74 healthy children, respectively. The corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg) and corneal-compensated intraocular pressure (IOPcc) were measured with the ocular response analyzer (ORA). Associations between ocular and diabetic parameters were also evaluated. There were no statistically significant differences between the two groups in age or gender distribution. The mean CH was 10.8 ± 1.5 and 10.7 ± 1.7 mmHg while the mean CRF was 10.9 ± 1.9 and 10.5 ± 1.6 mmHg in the diabetic group and control group, respectively. The mean IOPg was 15.9 ± 3.7 and 15.2 ± 3.4 mmHg, and the mean IOPcc was 15.8 ± 3.0 and 15.3 ± 3.4 mmHg in the diabetic and control group, respectively. There were no statistically significant differences between the two groups for CH, CRF, IOPg, and IOPcc measurements (independent t test, p = 0.624, p = 0.207, p = 0.263, p = 0.395, respectively). This study shows that type 1 DM does not have any effect on the corneal biomechanical parameters in childhood.     

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.     

Evaluation of Corneal Biomechanical Properties Following Penetrating Keratoplasty Using the Ocular Response Analyzer

Purpose

To evaluate corneal biomechanical properties in eyes that had previously undergone penetrating keratoplasty (PK) using the ocular response analyzer (ORA).

Methods

We recruited 26 patients who had received unilateral PK. Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and cornea-compensated intraocular pressure (IOPcc) were measured with the ORA and were compared to the measurements from the contralateral eyes that did not undergo PK.

Results

The CH was 8.95±2.59 mmHg in eyes that underwent PK and 9.78±1.45 mmHg in the contralateral eyes that did not undergo PK (p=0.077). The CRF was 10.26±2.64 mmHg in post-PK eyes and 9.75±1.45 mmHg in the contralateral eyes (p=0.509), and the CH-CRF was significantly smaller in post-PK eyes (-1.31±2.32 mmHg in post-PK eyes vs. 0.03±0.88 mmHg in fellow eyes, p=0.016). The IOPg and IOPcc were significantly higher in the PK group than they were in the control group. The IOPcc''s were 20.81±7.81 mmHg and 16.27±2.49 mmHg in post-PK and control eyes, respectively (p=0.011); and the IOPg''s were 19.22±7.34 mmHg and 15.07±3.03 mmHg in post-PK and control eyes, respectively (p=0.019). The IOPcc-g''s were 1.59±2.81 mmHg and 1.21±1.30 mmHg in post-PK and control eyes, respectively (p=0.412), and the central corneal thickness (CCT)''s were 489.11±90.60 µm and 556.24±42.84 µm in post-PK and control eyes, respectively (p=0.068).

Conclusions

Following PK, CH tended to decrease while CRF tended to increase, significantly decreasing CH-CRF. A significantly higher intraocular pressure and a thinner CCT following PK may have contributed to the observed changes in these corneal biomechanical parameters.     

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.     

Evaluation of corneal biomechanical properties following penetrating keratoplasty using ocular response analyzer

Purpose:

To evaluate corneal biomechanical properties in eyes that has undergone penetrating keratoplasty (PK).

Materials and Methods:

Retrospective observational study in a tertiary care centre. Data recorded included ocular response analyzer (ORA) values of normal and post-keratoplasty eyes [corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and cornea-compensated intraocular pressure (IOPcc)], corneal topography, and central corneal thickness (CCT). Wilcoxon signed rank test was used to analyze the difference in ORA parameter between post-PK eyes and normal eyes. Correlation between parameters was evaluated with Spearman''s rho correlation.

Results:

The ORA study of 100 eyes of 50 normal subjects and 54 post-keratoplasty eyes of 51 patients showed CH of 8.340 ± 1.85 and 9.923 ± 1.558, CRF of 8.846 ± 2.39 and 9.577 ± 1.631 in post-PK eyes and normal eyes, respectively. CH and CRF did not correlate with post-keratoplasty astigmatism (P =0.311 and 0.276, respectively) while a significant correlation was observed with IOPg (P =0.004) and IOPcc (P < 0.001).

Conclusion:

Biomechanical profiles were significantly decreased in post-keratoplasty eyes with significant correlation with higher IOP as compared with that in normal eyes.     

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。     

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.     

Effect of topical corneal anaesthesia on ocular response analyzer parameters: pilot study

Purpose The effect of topical corneal anaesthesia on corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal compensated IOP (IOPcc) was measured by ocular response analyzer (ORA). Design Observational, cross-sectional study. Method We examined both eyes of 23 healthy volunteers. Patients with external eye disease, previous refractive surgery, contact lenses or topical medication were excluded. ORA parameters were first measured in both eyes. Oxybuprocaïne 0.4% eye drop was instilled in the right eyes (RE) and physiologic saline in the left eyes (LE) as a control to rule out the lubrication effect. After 2 min, the ORA measurements were performed again. Goldmann applanation tonometry (GAT) was finally done. Data are expressed as mean ± standard deviation (SD). The medians of the four CH, CRF, IOPg, and IOPcc values measured before and after instillation were compared by using Wilcoxon signed ranks tests for RE and LE. Results The mean age was 39.5 ± 11.6 years. The mean GAT was 13.1 ± 2.5 mmHg for RE and 12.8 ± 2.5 mmHg for LE. In the RE, the respective values for the two sequences were IOPcc = 15.6 ± 2.6 mmHg and 15 ± 2.8 mmHg (P = 0.036); IOPg = 15.3 ± 3.3 mmHg and 15.4 ± 3.5 mmHg (P = 0.806); CH = 11 ± 1.3 mmHg and 11.1 ± 1.4 mmHg (P = 0.563); CRF = 11.1 ± 1.8 mmHg and 10.9 ± 1.9 mmHg (P = 0.053). In the LE, the respective values for the two sequences were IOPcc = 15.4 ± 2.6 mmHg and 15.6 ± 2.8 mmHg (P = 0.903); IOPg = 15.5 ± 3.5 mmHg and 15.4 ± 3.4 mmHg (P = 0.208); CH = 10.8 ± 1.4 mmHg and 10.7 ± 1.7 mmHg (P = 0.494); CRF = 10.7 ± 1.8 mmHg and 10.7 ± 2.2 mmHg (P = 0.626). Conclusion Two minutes after instillation, topical corneal anaesthetic slightly decreases IOPcc and also—but not statistically significantly—CRF. We did not find any statistical significant difference in CH or IOPg before and after topical corneal anaesthesia. Further investigation with more patients should be advised.     

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.