The associations between corneal biomechanical parameters and glaucoma / 中华实验眼科杂志

Glaucoma is one of the leading causes of blindness worldwide.Various factors are related to the development and progression of glaucoma.High intraocular pressure is an important risk factor.In recent years,many studies have focused on other potential risk factors for glaucoma,such as intraocular pressure-independent factors,including vascular factors,central corneal thickness,etc.The relationship between corneal biomechanical parameters and glaucoma has been attracting more and more attentions.The corneal biomechanics measurement instruments include ocular response analyzer (ORA) and corneal visualization scheimpflug technology (Corvis-ST),which are all commonly used in clinical practice.Some studies showed that the corneas in glaucoma patients were more easily to deform.Corneal biomechanical characteristics may reflect the anatomic structure weakness of the eyeball.For example,more easily deforming of cornea results in smaller tolerance of sclera and lamina cribros to intraocular pressure,which makes the optic disc more vulnerable.This may be one of the causes of glaucomatous optic nerve damage.Corneal biomechanical parameters have a certain extent relationship with the severity of glaucoma.In order to probe into the pathogenesis of glaucoma deeply,we reviewed corneal biomechanics characteristics,application of corneal biomechanical properties measuring instruments in clinical practice and the relationships between corneal biomechanics characteristics and the development and progression of glaucoma,as well as the therapeutic effectiveness of glaucoma.

Agreement between corneal-compensated intraocular pressure (IOPcc) and five corrected intraocular pressures and the correlation of ocular biometries with IOPcc and Goldmann correlated intraocular pressure / 眼科新进展

Objective To compare the agreement between corneal-compensated intraocular pressure (IOPcc) measured by ocular response analyzer (ORA) and 5 corrected intraocular pressures from Sirius anterior system,and analyze the correlation of ocular biometries with IOPcc and Goldmann-correlated IOP (IOPg).Methods Together 90 eyes of 90 patients,aged 18-37 (24.47 ± 5.57) years,without refractive surgery contraindications undergoing myopic laser treatment were enrolled in this study.Each eye was measured 3 times by Sirius anterior system,with the best results of IOPcc and IOPg was selected.And patients' corneal biomechanical parameters were measured using an ORA (Reichert,Inc.,USA).The IOPg from ORA were entered into the 5 IOP formulas embedded in Sirius anterior system to generate the corrected IOPs,which were recorded as the Dresdner corrected IOP,Ehlers corrected IOP,Kohlhaas corrected IOP,Orssengo/Pye corrected IOP and Shah corrected IOP,accordingly.Meanwhile the agreement of the 5 corrected IOPs and the IOP measured non-contact tonometer with IOPcc was analyzed,respectively.Corneal biomechanics,including corneal hysteresis and corneal resistance factor,and ocular biometries were also recorded,and the correlation of these parameters with IOPcc and IOPg was assessed with correlation coefficient.Resuits The pair comparison of IOPcc and Kohlhaas corrected IOP was statistically significant (P ＜ 0.05).Dresdner corrected IOP and Orssengo/Pye corrected IOP showed a good agreement with IOPcc,and the 95％ limits of agreements (LoA) were (-2.09 ～2.55)mmHg (1 kPa=7.5 mmHg) and (-2.38～2.37) mmHg,respectively.The 95％LoA of Dresdner's corrected IOP and IOPcc was the narrowest.No statistical significance was found between IOPcc and corneal hysteresis,corneal resistance factor,ocular biometries,but there was a positive correlation between IOPg and corneal resistance factor,central corneal thickness,and corneal volume (all P ＜ 0.05).Conclusion Dresdner and Orssengo/Pye corrected IOP had a good agreement with IOPcc,and most ocular biometries have a little effect on IOPcc.

Comparison on biomechanical stability between femtosecond laser assisted LASIK and LASEK with ocular response analyzer / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To compare the difference of biomechanical stability after a femtosecond laser-assisted <i>in situ</i> keratomileusis(FS-LASIK)and laser-assisted subepithelial keratomileusis(LASEK)by ocular response analyzer(ORA). <p>METHODS: This prospective study was conducted at the First Affiliated Hospital of Harbin Medical University, and myopic patients with the equivalent sphere between -2.00 and -5.00 diopters from January 2016 and December 2017 were enrolled. All the subjects were divided into FS-LASIK and LASEK group respectively according to different surgical methods. There were 64 patients(100 eyes)participated in the FS-LASIK group while 53 patients(100 eyes)in the LASEK surgery group. Corneal hysteresis value(CH)and corneal resistance factor value(CRF)were measured pre-, 1mo and 3mo postoperation of all the subjects. And the variance analysis of two groups was repeated to compare the overall difference between the two modes of operation from pre-operation to post operation. <p>RESULTS: The CH and CRF value of the two groups were different before and after operation(<i>P</i><0.05). The comparison results of repeated measurements showed that the CH value and CRF value of the surgical methods were reduced in 1 and 3mo after operation, respectively, and there was significance(<i>P</i><0.05). The CH and CRF of FS-LASIK group was lower than LASEK group only in 1mo after the operation(<i>P</i><0.05). <p>CONCLUSION: Both surgeries could affect the biomechanical stability of cornea. From the point of view of biomechanical stability, LASEK operation is safer than FS-LASIK operation and reduces the possibility of postoperative refractive regression.

Detection of the early keratoconus based on corneal biomechanical properties in the refractive surgery candidates.

Context: Subclinical keratoconus is contraindication to refractive surgery. The currently used methods of preoperative screening do not always allow differentiating between healthy eyes and those with subclinical keratoconus. Aim: To evaluate biomechanical parameters of the cornea, waveform score (WS), and intraocular pressure (IOP) as potentially useful adjuncts to the diagnostic algorithm for precise detection of the early keratoconus stages and selection of refractive surgery candidates. Settings and Design: Department of Ophthalmology and prospective cross‑sectional study. Patients and Methods: Patients enrolled in the study were diagnosed with refractive disorders. We assessed parameters of corneal biomechanics such as corneal hysteresis (CH), corneal resistance factor (CRF), Goldman‑correlated IOP (IOPg), corneal compensated IOP, WS, and keratoconus match index (KMI). They were classified into one of three groups based on the predefined KMI range: Group 1 (from 0.352 to 0.757) – 45 eyes, Group 2 (from −0.08 to 0.313) – 52 eyes, and Group 0 ‑ control group (from 0.761 to 1.642) – 80 eyes. Results: In both study groups, IOPg, CRF, and CH were decreased when compared to control (P < 0.0001). In control group, there was positive correlation between CH and KMI (P < 0.05), with no correlations in any of the two study groups. CRF correlated positively with KMI in control (P < 0.0001) and in Group 2 (P < 0.05). Conclusions: CH and CRF, together with WS and IOPg, consist a clinically useful adjunct to detect subclinical keratoconus in patients referred for refractive surgery when based on KMI staging.

Progress on the measurement of corneal biomechanical properties / 国际眼科杂志(Guoji Yanke Zazhi)

Cornea is the major refractive components of the eye. As a viscoelastic tissue, cornea exhibits complicated biomechanical properties: non - linear elasticity, anisotropy and viscoelasticity. The biomechanical properties play an important role in keeping the normal structureand function. Changes in biomechanical properties are always earlier than the clinical symptoms. So quantitative measurement of the biomechanical properties benefits the early diagnosis and treatment of diseases. Different methods to measure the biomechanical properties of cornea were reviewed in detail, including classic ex vivo destructive tests, commercially available in vivo measuring methods and other emerging methods with the potential for clinical application but not validated for in vivo measurement. The operating principles, advantages as well as limitations of these methods were also described.

The latest progress of corneal biomechanical measurement and its clinical application / 医学研究生学报

Cornea is a very important component of the human eyeball wall.It maintains the physiological structure of eyeball and provides protection for eye content and it is an important part of refractive media.As human inhomogeneous viscoelastic material, the cornea possesses many biomechanical properties such as the elastic, viscosity and non linear elastic.Currently, ocular response an-alyzer and corneal visualization scheimpflug technology are often used in vivo measurement and analysis to assist in the diagnosis and treatment of clinical diseases such as keratoconus, and to assess the feasibility and prognosis of refractive surgery.The latest progress of corneal biomechanical measurement and its clinical application are reviewed in this paper.

Comparación en la medición de presión intraocular con los tonómetros de Goldmann, Pascal® y ORA (Ocular Response Analyzer) / Intraocular pressure measurement with Goldmann, Pascal and ORA tonometers

Introducción: el glaucoma es la principal causa de ceguera irreversible en el mundo, siendo la presión intraocular alta el factor de riesgo más importante para desarrollarlo, por eso la importancia de realizar una adecuada medición de la presión intraocular (PIO) durante el examen oftalmológico. Objetivo: evaluar la concordancia de la medida de la presión intraocular tomada con los tonómetros de Goldmann, Pascal® y ORA, en pacientes con glaucoma de la consulta externa del servicio de oftalmología del Hospital de San José. Diseño: estudio descriptivo, de corte transversal y concordancia. Métodos: se compararon las medidas de Goldmann corregido, Pascal® y ORA corregido en 90 pacientes (167 ojos) con diagnóstico de glaucoma que asisten a consulta de oftalmología del Hospital de San José. Resultados: el coeficiente de correlación y concordancia de Lin entre Goldmann corregido y Pascal® es de 0.61; entre Goldmann corregido y ORA corregido de 0.64 y entre Pascal® y ORA corregido de 0.81. Conclusiones: se encontró una concordancia moderada para los tres tonómetros en la medición de la PIO en los ojos con glaucoma del servicio de oftalmología del Hospital de San José. Los tres métodos no son reemplazables, por lo tanto el seguimiento de los pacientes siempre debe ser tomado con un mismo método.

Introduction: glaucoma is the leading cause of worldwide irreversible blindness, high intraocular pressure remains the most important risk factor; because of that, it is essential to measure accurately the intraocular pressure (IOP). Objective: to evaluate the intraocular pressure correspondence of Goldmann-correlated IOP, Pascal® dynamic contour tonometer and Reichert Ocular Response Analyzer ORA tonometers in patients with glaucoma diagnosis at Ophthalmology Service, Hospital de San José. Design: a descriptive, cross-sectional and matching. Methods: measurements of Goldmann correlated IOP, Pascal® and ORA corneal compensated IOP were compared, in patients (167 eyes) diagnosed with glaucoma attending at ophthalmology Hospital San José. Results: the correlation coeffi cient and concordance Lin between Goldmann correlated IOP and Pascal® is 0.61; between ORA and Goldmann correlated IOP is 0.64 and between Pascal® and ORA is 0.81. Conclusions: we found a moderate agreement for the three tonometers for measuring IOP in eyes glaucoma attending at ophthalmology Hospital San José. The three methods are not replaceable, therefore monitoring of patients should always be taken with the same method.

Diagnostic Availability of Ocular Response Analyzer in Korean Patients with Normal Tension Glaucoma

PURPOSE: To compare the parameters measured with the ocular response analyzer (ORA; Reichert Inc., Depew, NY, USA) between normal control subjects and patients with normal tension glaucoma (NTG) and to investigate clinical usefulness of ORA. METHODS: Intraocular pressure (IOP) and central corneal thickness (CCT) were measured using the Goldmann applanation tonometer (GAT) in 100 eyes of 100 normal subjects and 100 eyes of 100 NTG patients. Four types of ORA parameters, corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated IOP (IOPg), and corneal-compensated IOP (IOPcc) were also measured. RESULTS: The mean CH values were 11.2 mm Hg and 10.3 mm Hg and the mean CRF values were 10.8 mm Hg and 9.9 mm Hg in the normal subjects group and the NTG group, respectively. Mean CH and CRF were significantly lower in NTG patients (p < 0.001) and the IOPcc were higher than normal subjects (p = 0.004). IOPg was in agreement with the GAT IOP (ICC = 0.811) and IOPcc was not correlated with CCT. The cut-off value of 'IOPcc - IOPg' as the diagnostic standard parameter was -0.05 mm Hg (sensitivity; 76%, specificity; 55%). CONCLUSIONS: IOPg measurements were similar to GAT IOP, and other ORA parameters (CH, CRF, IOPcc) were significantly different between normal subjects and NTG patients. Consequently, the difference of IOPcc and IOPg could be a useful parameter in NTG diagnosis.

Diurnal Variation in Intraocular Pressure Measured by Ocular Response Analyzer in Korean Patients with Normal Tension Glaucoma

PURPOSE: To analyze the diurnal change in intraocular pressure (IOP) and corneal biomechanical properties measured using the Ocular Response Analyzer (ORA; Reichert Inc., Depew, NY, USA) in Korean patients with normal tension glaucoma (NTG) patients. METHODS: Intraocular pressure (Goldmann applanation tonometer IOP [GAT IOP], Goldmann-correlated IOP [IOPg], corneal-compensated IOP [IOPcc]) and corneal hysteresis (CH), corneal resistance factor (CRF) and central corneal thickness (CCT) were measured in 21 eye of NTG patients (12 males, 9 female) at 3 hour intervals for 48 hours using ORA. We recorded the time of each parameter that showed the lowest and the highest values of during the 48 hour testing period (Day 1 and Day 2) and evaluated the change of diurnal variation using Repeated measures analysis of variance (Re-ANOVA). RESULTS: Peak IOP measured with GAT and ORA occurred at 6 AM-9 AM, 3 PM-6 PM and the trough IOP at 9 PM-12 AM during the 48 hour period. CCT, GAT IOP, IOPcc and IOPg measurements showed statistically significant variations (p0.05). CONCLUSIONS: In Korean NTG patients, IOP exhibits significant diurnal variation, with higher values during the dawn and afternoon and lower values before retiring. Clinically, measurements of IOP performed in the afternoon could aid in the detection of relatively elevated IOP.

Change in Corneal Biomechanical Parameters in Diabetes Mellitus

PURPOSE: In this study, we examined the changes in corneal biomechanical parameters in patients with diabetes mellitus (DM). METHODS: Fifty patients with DM were divided into 2 subgroups, 25 diabetic patients with glycated hemoglobin (HbA1c 7%) and compared with the eyes of 80 healthy subjects. Corneal biomechanical parameters were measured using ocular response analyzer (ORA). Differences in corneal biomechanical properties between healthy subjects and diabetic patients were compared. Additionally, differences in corneal biomechanical properties between diabetic patients with HbA1c 7% were compared. RESULTS: Corneal hysteresis, corneal resistance factor and central corneal thickness (CCT) were statistically significantly higher in patients with diabetes compared to healthy subjects. Goldmann tonometer, non-contact tonometer and Goldmann-correlated intraocular pressure (IOPg) were statistically significantly higher in patients with DM compared to healthy subjects, but corneal compensated IOP (IOPcc) was not statistically significantly different between healthy subjects and diabetic patients. However, corneal biomechanical parameters, which were statistically significantly different between healthy subjects and DM patients, were not statistically significantly different between diabetic patients with HbA1c 7%. CONCLUSIONS: Considering that corneal properties are different between diabetic patients and healthy subject, IOPcc measured with ORA is considered clinically useful for measuring IOP as it reflects CCT and biomechanical properties that should be revised. In diabetes, changes in corneal biomechanical properties depend on long-term glucose control rather than short-term glucose control.

Corneal Biomechanical Properties of Normal Tension Glaucoma in Young Patients Evaluated with the Ocular Response Analyzer

PURPOSE: To evaluate the corneal biomechanical properties and clinical characteristic of normal tension glaucoma (NTG) in young patients. METHODS: We compared corneal biomechanical properties using an Ocular response analyzer (ORA) of under age 40 of 37 eyes of patients with NTG and 42 eyes of normal group. RESULTS: The mean corneal resistance factor (CRF) and mean corneal hysteresis (CH) were significantly lower in NTG eyes (CRF, 9.2 +/- 2.1 mm Hg; CH, 9.8 +/- 1.8 mm Hg) than in normal eyes (CRF, 10.7 +/- 2.3 mm Hg; CH, 10.9 +/- 2.0 mm Hg; p = 0.01, p < 0.01). CH and CRF were associated with central corneal thickness (CCT) (CH; beta = 0.354, p < 0.01, CRF; beta = 0.348, p < 0.01) and glaucoma status (p < 0.01, p < 0.01). CONCLUSIONS: The CRF and CH were significantly lower in NTG group while IOP cc was not significantly different between the group. In diagnosing the NTG in young patients, ORA maybe useful for distinguishing between the glaucoma eyes and normal eyes.

The Association Between Corneal Biomechanical Properties and Progression of Visual Field Loss in Normal Tension Glaucoma

PURPOSE: To evaluate the association between corneal biomechanical properties and progression of visual field loss in normal tension glaucoma. METHODS: This study enrolled 73 eyes of 73 patients with normal tension glaucoma who were undergoing medical treatment, and classified them into progressing and nonprogressing groups by visual field trend analysis. The corneal biomechanical properties measured by the Ocular Response Analyzer (ORA; Reichert Instruments, Depew, NY, USA), central corneal thickness, and Goldmann applanation tonometry were comparatively analyzed between the 2 groups. RESULTS: Twenty-six eyes reached a progression endpoint. The prevalence of hypertension was higher in the progressing group (42.3%, progressing, 17.0%, nonprogressing; p = 0.03). Progressing eyes had lower corneal hysteresis (9.1 +/- 1.3 vs. 9.8 +/- 1.5 mm Hg, p = 0.03) and lower corneal resistance factor (9.5 +/- 1.5 vs. 10.4 +/- 1.4 mm Hg, p = 0.01) compared with nonprogressing eyes. Upon multivariate analysis, the presence of hypertension (odds ratio [OR] = 3.46, p = 0.03) and corneal hysteresis (CH) (OR = 0.66 per mm Hg lower, p = 0.02) remained statistically significant. CONCLUSIONS: The CH measurement with ORA was significantly associated with risk of visual field progression in normal tension glaucoma. Eyes with lower CH had a greater risk of progression of visual field loss than those with higher CH.

Biomechanical Property of Keratoconus Measured by ORA

PURPOSE: To compare the biomechanical properties of keratoconus, keratoconus suspect, and normal subjects measured by ocular response analyzer. METHODS: A total of 72 patients were divided into 3 groups: keratoconus, suspected keratoconus, and normal control subjects. The 3 age-matched groups were evaluated according to age, sex, and visual acuity. Slit lamp examinations, Pentacam, and ocular response analyzer (ORA) examinations were performed. Mean corneal refractive power, central corneal thickness, corneal hysteresis (CH), and corneal resistance factor (CRF) were evaluated and analyzed. RESULTS: Twenty-four eyes were included in each group. The mean age was 23.8 years in keratoconus, 26.0 years in suspected keratoconus and 26.1 years in normal subject groups. Mean corneal refractive power was significantly higher in keratoconus (p < 0.001) and suspected keratoconus (p = 0.001) groups than in the normal subject group. Mean central corneal thickness showed significant differences among the 3 groups (p < 0.05). CH was significantly lower in keratoconus than suspected keratoconus (p = 0.025) and normal subject groups (p = 0.005), but showed no significant difference between suspected keratoconus and normal subject groups. CRF showed significant differences among all 3 groups (p < 0.05). CH and CRF had negative correlations with mean corneal refractive power and positive correlations with central corneal thickness. CONCLUSIONS: CH and CRF measured by ORA were significantly different between keratoconus and normal subject groups and had significant correlations with mean corneal refractive power and central corneal thickness. CRF may be a useful method to differentiate between suspected keratoconus and normal cornea patients.

The development of the applications of ocular response analyzer in excimer laser surgery / 眼科研究

Research on the application of ocular response analyzer has become one of the main issues in ophthalmology.The ocular response analyzer has been used in the measurement of ocular bioparameters of glaucoma,cataract,heretability and refractive surgery.As a newly invented non-contact tonometric device,the ocular response analyzer is helpful not only in the measurement of intraocular pressure (IOP),but also in the determination and calculation of two corneal biomechanical properties:corneal hysteresis (CH) and corneal resistance factor (CRF).It offers the possibility of measuring corneal biomechanical properties in vivo.This article primarily reviewed the application of the ocular response analyzer in terms of pre-operative examination and post-operative follow-up in excimer laser surgery.

Factors Affecting the Ocular Response Analyzer Parameters in Normal Korean

PURPOSE: To identify the normal range of factors which can be measured with Ocular Response Analyzer (ORA, Reichert Inc., Depew, NY, USA) in normal Korean, and to analyze factors affecting ORA by measuring intraocular pressure (IOP) of noncontact tonometer (NCT) and central corneal thickness (CCT). METHODS: Three hundred and one normal Korean subjects who did not have specific ophthalmological diseases and surgeries in the past were recruited for this study. Corneal hysteresis (CH), corneal response factor (CRF), corneal-compensated IOP (IOPcc), and Goldmann correlated IOP (IOPg) were measured using ORA. In addition, IOP of NCT and CCT were measured and the results and factors analyzed. RESULTS: The mean CH measured among normal Korean subjects in this study was 10.70 mmHg. The mean CRF was 10.40 mmHg. CH and CRF were significantly higher in the juvenile group. IOPcc and IOPg as measures of IOP using the ORA had significant correlation with IOP of NCT. In particular, IOPcc appeared to be independent of CCT. CONCLUSIONS: CH and CRF were different according to age, indicating a difference in biomechanical properties of the cornea. In particular, IOPcc is more important as it is independent of corneal thickness and should be compensated in general measurements of IOP reflecting biomechanical properties.