Research progress on the stress-strain index of Corvis ST / 国际眼科杂志(Guoji Yanke Zazhi)

Corneal visualization Scheimpflug technology(Corvis ST)is currently the most commonly used clinical device for assessing in vivo corneal biomechanics. The new parameter stress-strain index(SSI)has been a hot topic of clinical research in recent years, which not only directly reflect corneal biomaterial stiffness, but also closely correlates with the progression of certain diseases. SSI was generated based on the predictions of corneal behavior using finite element(FE)numerical modeling to simulate the effects of intraocular pressure and Corvis ST jets. The SSI algorithm does not change with central corneal thickness(CCT), intraocular pressure, or biomechanically corrected intraocular pressure(BIOP), but it is clearly associated with altered collagen fibres in the corneosclera. The principles of SSI, the relationship between age and SSI, the relationship between axial length and SSI, the relationship between myopia and SSI, and the application of SSI are summarized and concluded.

In vivo corneal elastography: A topical review of challenges and opportunities.

Clinical measurement of corneal biomechanics can aid in the early diagnosis, progression tracking, and treatment evaluation of ocular diseases. Over the past two decades, interdisciplinary collaborations between investigators in optical engineering, analytical biomechanical modeling, and clinical research has expanded our knowledge of corneal biomechanics. These advances have led to innovations in testing methods (ex vivo, and recently, in vivo) across multiple spatial and strain scales. However, in vivo measurement of corneal biomechanics remains a long-standing challenge and is currently an active area of research. Here, we review the existing and emerging approaches for in vivo corneal biomechanics evaluation, which include corneal applanation methods, such as ocular response analyzer (ORA) and corneal visualization Scheimpflug technology (Corvis ST), Brillouin microscopy, and elastography methods, and the emerging field of optical coherence elastography (OCE). We describe the fundamental concepts, analytical methods, and current clinical status for each of these methods. Finally, we discuss open questions for the current state of in vivo biomechanics assessment techniques and requirements for wider use that will further broaden our understanding of corneal biomechanics for the detection and management of ocular diseases, and improve the safety and efficacy of future clinical practice.

Changes in corneal biomechanics after small incision lenticule extraction and femtosecond laser-assisted laser in situ keratomileusis evaluated by corneal visualization Scheimpflug technology / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To evaluate the changes in corneal biomechanics of patients with moderate refractive error after receiving small-incision lenticule extraction(SMILE)and femtosecond laser-assisted laser in situ keratomileusis(FS-LASIK)using the corneal visualization Scheimpflug technology(Corvis ST).METHODS:Prospective cohort study. A total of 65 moderate myopia patients(65 eyes)who were scheduled to undergo refractive surgery at the Ophthalmic Refractive Surgery Center of the Ningxia Eye Hospital from November 2020 to November 2021 were included in the study, and there were 30 eyes in the SMILE group and 35 eyes in the FS-LASIK group. The changes in corneal biomechanical parameters, including integrated radius(IR), inverse concave radius(ICR), deformation amplitude ratio 2mm(DAR2), stiffness parameter at first applanation(SP-A1), ambrosio relational thickness(ARTh)and the central curvature radius at highest concavity(HC-Radius)were observed by Corvis ST between both groups preoperatively and 1 and 3mo postoperatively.RESULTS: There were no statistical significance in biomechanical parameters between two groups of patients 1 and 3mo postoperatively(P>0.05). IR, ICR and DAR2 of each groups of patients 1 and 3mo postoperatively were significantly increased than those preoperatively, and SP-A1, ARTh and HC-Radius were significantly decreased than those preoperatively(all P<0.05). The biomechanical parameters at 1mo and 3mo postoperatively showed no statistical significance(P>0.05). In addition, a positive correlation was found between central corneal thickness(CCT)and ARTh and SP-A1 of the two groups of patients at 3mo postoperatively(FS-LASIK group: r=0.727, 0.819, SMLIE group: r=0.683, 0.434, all P<0.05), while a negative correlation was found between CCT and IR and ICR at 3mo postoperatively.(FS-LASIK group: r=-0.697, -0.622, SMLIE group: r=-0.447, -0.491, all P<0.05).CONCLUSION:For patients with moderate myopia, both SMILE and FS-LASIK can reduce corneal biomechanical stability. Both surgeries showed no significant differences in the effect on biomechanical, and the biomechanical has been stabilized at 1mo postoperatively. A correlation was found between postoperative CCT and ARTh, SP-A1, IR and ICR.

Characteristics of new corneal biomechanical parameters in different degrees of myopia / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To study the characteristics of new corneal biomechanical parameters in different degrees of myopia and analyze the correlation of the new parameter stress-strain index(SSI).METHODS: A cross-sectional study was conducted on 366 adult patients(718 eyes)with different degrees of myopia who received treatment at the First Affiliated Hospital of Dali University from October 2021 to November 2021, aged 18-50 years, and the spherical equivalent(SE)was -0.50～-16.75D. The axial length(AL)of the eye was measured by IOL master, and the new corneal biomechanical parameters, central corneal thickness(CCT)and intraocular pressure(IOP)were measured by corneal visualization Scheimpflug technology(Corvis ST). The subjects were categorized into low myopia, moderate myopia and high myopia groups according to SE. The data were analyzed by ANOVA and Pearson correlation.RESULTS: The ratio of the thinnest corneal thickness to horizontal thickness change rate(ARTh)and SSI were statistically significant(P<0.001), while the remaining parameters were not statistically significant(P>0.05). SSI was positively correlated with age(r=0.102, P=0.006), SE(r=0.361, P<0.001), IOP(r=0.175, P<0.001), CCT(r=0.098, P=0.009), SPA1(r=0.182, P<0.001), negatively correlated with AL(r=-0.331, P<0.001), IR(r=-0.545, P<0.001)and had no correlation with other corneal biomechanical parameters(P>0.05).CONCLUSION: With the increase of myopia degree and the elongation of the axial length, the SSI value becomes smaller and the corneal hardness decreases. SSI may be a helpful corneal biomechanical indicator for future research on myopia.

Corrigendum: A potential screening index of corneal biomechanics in healthy subjects, forme fruste keratoconus patients and clinical keratoconus patients.

[This corrects the article DOI: 10.3389/fbioe.2021.766605.].

Correlation analysis between corneal biomechanical parameters and high-order aberrations in myopia children / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To investigate the correlation between corneal biomechanical parameters measured by the corneal visualization Scheimpflug Technology(Corvis ST)and corneal high-order aberrations(HOAs)in children with mild to moderate myopia.METHODS:A cross-sectional study. A total of 255 pediatric patients with myopia enrolled from April to July 2021 in Tianjin Medical University Eye Hospital were continuously collected, and all the right eyes were taken for analysis. Corneal biomechanical parameters were obtained from Corvis ST. Pentacam three-dimensional anterior segment analyzer was used to measure total corneal higher-order aberrations(RMSh), third order aberrations(RMS3)and fourth order aberrations(RMS4).RESULTS:RMS3 was positively correlated with the second applanation time(A2T)(r=0.175, P=0.009)and negatively correlated with the axis length(AL)(r=-0.155, P=0.014). RMS4 was negatively correlated with the highest concavity radius(HCR)(r=-0.165, P=0.009). RMSh was negatively correlated with HCR and AL(r=-0.152, P=0.037; r=-0.175, P=0.005).CONCLUSION:There is a correlation between corneal biomechanical parameters and HOAs in children with myopia. Cornea with higher stiffness and stronger deformation resistance has smaller RMS3, RMS4 and RMSh.

Comparative analysis of the morphological and biomechanical properties of normal cornea and keratoconus at different stages.

PURPOSE: To compare the morphological and biomechanical properties of normal cornea and keratoconus at different stages. METHODS: A total of 408 patients (517 eyes) with keratoconus were included in this study. According to the Topographic Keratoconus (TKC) grading method, keratoconus was divided into stage I (TKC = 1, 130 eyes), stage II (TKC = 1-2, 2, 164 eyes), stage III (TKC = 2-3, 3, 125 eyes) and stage IV (TKC = 3-4, 4, 98 eyes). A total of 158 normal subjects (158 eyes) were recruited as the normal group. The corneal morphological parameters and biomechanical parameters were obtained with Scheimpflug tomography (Pentacam) and corneal visualization Scheimpflug technology (Corvis ST), and the receiver operating characteristic (ROC) curves were drawn. RESULTS: Each corneal morphological and most biomechanical parameters of the keratoconic eyes were significantly different from those of the normal eyes in this study (p < 0.001). ROC curve demonstrated that most parameters in this study showed high efficiency in diagnosing keratoconus (the area under the ROC (AUC) was > 0.9), with the Belin-Ambrósio deviation (BAD-D) and Tomographic and Biomechanical Index (TBI) showing higher efficiency. The efficiency of BAD-D and TBI was high in differentiating keratoconus at different stages (AUC > 0.963). The comparison of ROC curves of keratoconus at different stages did not reveal statistically significant differences for TBI. CONCLUSION: BAD-D and TBI can effectively diagnose stage I keratoconus. Moreover, the efficiency of TBI is the same in diagnosing keratoconus at all stages, while the diagnostic efficiency of other parameters increases with the increase in keratoconus stages.

Corneal biomechanical properties after soft contact lens wear measured on a dynamic Scheimpflug analyzer: A before and after study.

OBJECTIVES: To evaluate the corneal biomechanics before and after daily use of contact lenses (CLs), measured by Scheimpflug-based devices. METHODS: This prospective clinical study includes participants who were scheduled to use CLs daily for refractive error. The biomechanical parameters were measured by the Corneal Visualization Scheimpflug Technology (Corvis ST) before and one month after using the soft CLs. RESULTS: Twenty-three subjects (46 eyes), including 16 female (76.2%) with a mean age of 28±7.29 years, were enrolled. There was no significant difference among biomechanical factors measured before and after contact lens wear (P>0.05). Using regression analysis of the biomechanical markers, we found a statistically significant association between second applanation length (A2 length) (P=0.001), highest concavity radius (HCR) (P=0.05), deflection amplitude ratio (DA_ratio) (P=0.05) and integrated radius (P<0.001) with age. Regarding spherical equivalent, we found a statistically significant association between central corneal thickness (CCT) (P=0.05), A2 length (P=0.03) and stiffness parameter at first applanation (SPA1) (P=0.02). CONCLUSIONS: We did not find a significant difference in terms of corneal biomechanical parameters between baseline and month 1; but regression analyses showed a statistically significant association between A2 length, HCR, DA_ratio, integrated radius, CCT and SPA1 and certain subject characteristics.

Influence of Corneal Visualization Scheimpflug Technology Tonometry on Intraocular Pressure.

Purpose: To investigate the effect of Corneal Visualization Scheimpflug Technology tonometry (CST) on intraocular pressure (IOP). Design: Cohort study. Participants: Patients with and without primary open-angle glaucoma (POAG) were included. Methods: Intraocular pressure was measured using the Icare rebound tonometer (ICRT; Icare Finland Oy) and the biomechanically corrected IOP (bIOP) using the CST. Intraocular pressure was measured at baseline with ICRT, followed by a CST measurement in one eye with the fellow eye acting as a control. Icare measurements were repeated at 10 seconds and 1, 2, 4, 8, 15, 30, and 60 minutes in both eyes. The ratio of test eye IOP to fellow eye IOP was used to control for intrasubject variation. Main Outcome Measures: Intraocular pressure change following Corneal Visualization Scheimflug Technology tonometry. Results: Forty participants (mean age, 54.09 ± 20.08 years) were included comprising 20 patients with POAG and 20 patients with no ocular abnormalities other than cataract. Mean central corneal thickness was similar in those without POAG (547.4 ± 55.05 µm) and with POAG (520.22 ± 37.59 µm; P = 0.14). No significant change was found in IOP measured with the ICRT in the fellow eye versus the 1-hour period in either the healthy (P = 0.87) or POAG (P = 0.92) group. Significant changes were found in IOP after CST measurement for both healthy (P < 0.01) and glaucomatous (P < 0.01) eyes. After the CST measurement, the IOP reduced continuously from a mean of 13.75 mmHg to 10.84 mmHg at 4 minutes for healthy eyes and from 13.28 mmHg to 11.11 mmHg at 8 minutes for glaucomatous eyes before approaching (83% for healthy eyes and 92% POAG eyes) the pre-CST measurement at 1 hour. Conclusions: Corneal Visualization Scheimpflug Technology tonometry causes a significant reduction in IOP in both glaucomatous and healthy eyes that lasts for at least 1 hour afterward.

Relationship between corneal stiffness parameters and lamina cribrosa curvature in normal tension glaucoma.

PURPOSE: To evaluate the relationship between corneal biomechanical parameters and lamina cribrosa (LC) curvature in normal tension glaucoma (NTG). METHODS: 95 eyes of 56 NTG patients were enrolled in this prospective, observational study. Corneal biomechanical parameters, including stiffness parameters at applanation 1 (SP-A1), deformation amplitude ratio (DA ratio), inverse concave radius and biomechanically corrected intraocular pressure estimate (bIOP), were captured using the Corneal Visualization Scheimpflug Technology instrument (Corvis-ST). LC curvature was evaluated by mean adjusted LC curvature index (maLCCI) averaged by the measurements on 12 radial B-scan images obtained using swept-source optical coherence tomography (SS-OCT). Linear mixed models were constructed to assess the relationship between corneal biomechanical parameters and LC curvature. RESULTS: The mean age of participants was 51.04 ± 13.74 years (range, 24-82 years). The SP-A1 and maLCCI were 93.50 ± 13.82 mm Hg/mm and 7.57 ± 1.58, respectively. In univariate and multivariate analysis, SP-A1 (p < 0.001 and p = 0.001) and age (p = 0.010 and p = 0.024) were both significantly associated with maLCCI. The LC curvature increased with softer cornea demonstrated by lower SP-A1 and younger eyes. There was no statistical significance interaction between SP-A1 and age (p = 0.194). CONCLUSIONS: The greater posterior LC curvature was associated with lower corneal stiffness parameters and younger eyes in NTG patients. CLINICAL TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR1900021465.

A Potential Screening Index of Corneal Biomechanics in Healthy Subjects, Forme Fruste Keratoconus Patients and Clinical Keratoconus Patients.

Purpose: This study aims to evaluate the validity of corneal elastic modulus (E) calculated from corneal visualization Scheimpflug technology (Corvis ST) in diagnosing keratoconus (KC) and forme fruste keratoconus (FFKC). Methods: Fifty KC patients (50 eyes), 36 FFKC patients (36 eyes, the eyes were without morphological abnormality, while the contralateral eye was diagnosed as clinical keratoconus), and 50 healthy patients (50 eyes) were enrolled and underwent Corvis measurements. We calculated E according to the relation between airpuff force and corneal apical displacement. One-way analysis of variance (ANOVA) and receiver operating characteristic (ROC) curve analysis were used to identify the predictive accuracy of the E and other dynamic corneal response (DCR) parameters. Besides, we used backpropagation (BP) neural network to establish the keratoconus diagnosis model. Results: 1) There was significant difference between KC and healthy subjects in the following DCR parameters: the first/second applanation time (A1T/A2T), velocity at first/second applanation (A1V/A2V), the highest concavity time (HCT), peak distance (PD), deformation amplitude (DA), Ambrosio relational thickness to the horizontal profile (ARTh). 2) A1T and E were smaller in FFKC and KC compared with healthy subjects. 3) ROC analysis showed that E (AUC = 0.746) was more accurate than other DCR parameters in detecting FFKC (AUC of these DCR parameters was not more than 0.719). 4) Keratoconus diagnosis model by BP neural network showed a more accurate diagnostic efficiency of 92.5%. The ROC analysis showed that the predicted value (AUC = 0.877) of BP neural network model was more sensitive in the detection FFKC than the Corvis built-in parameters CBI (AUC = 0.610, p = 0.041) and TBI (AUC = 0.659, p = 0.034). Conclusion: Corneal elastic modulus was found to have improved predictability in detecting FFKC patients from healthy subjects and may be used as an additional parameter for the diagnosis of keratoconus.

Corneal biomechanical alterations after phacoemulsitication with 2.4mm corneal incision / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To investigate the corneal biomechanical parameters alteration after phacoemulsitication with 2.4mm corneal incision within 1mo by Corvist ST.<p>METHODS: A self control study was performed. Twenty-eight age related cataract patients(56 eyes), who were in accordance with the inclusion criteria, received phacoemulsification with 2.4mm corneal incision from March to September in 2019. Corneal biomechanical parameters were measured preoperatively and postoperatively on 3d, 6d and 30d by Corvis ST.<p>RESULTS: The first applanation length(A1L), the second applanation time(A2T)and corneal thickness(CCT)were significantly different between preoperation and postoperation(<i>F</i>=10.534, 11.655, 14.734; all <i>P</i><0.05). The value of A1L on 3d postoperative was significantly increased than that on the day before operation, 6d and 30d postoperative, while the A2T value was significantly reduced(<i>P</i><0.05). But there was no different in A2L and A2T between preoperation and 6d postoperative(<i>P</i>>0.05). The value of central corneal thickness(CCT)was significantly increased on 3d and 6d postoperative compared with the preoperative parameter(<i>P</i><0.05). The value of CCT got the maximum value on the 3d after surgery, and recovered to the preoperative level on the 30d after surgery. <p>CONCLUSION: Phacoemulsitication with 2.4mm corneal incision change the corneal biomechanical preoperties. The corneal biomechanical parameters are basically recovered in the 30d postoperative.

Keratoconus Detection Based on a Single Scheimpflug Image.

Purpose: To introduce a new approach for keratoconus detection based on corneal microstructure observed in vivo derived from a single Scheimpflug image. Methods: Scheimpflug single-image snapshots from 25 control subjects and 25 keratoconus eyes were analyzed; from each group, five subjects were randomly selected to provide out-of-sample data. Each corneal image was segmented, after which the stromal pixel intensities were statistically modeled with a Weibull distribution. Distribution estimated parameters α and ß, characterizing corneal microstructure, were used in combination with a macrostructure parameter, central corneal thickness (CCT), for the detection of keratoconus. In addition, receiver operating characteristic curves were used to determine the sensitivity and specificity of each parameter for keratoconus detection. Results: The combination of CCT (sensitivity = 88%; specificity = 84%) with microscopic parameters extracted from statistical modeling of light intensity distribution, α (sensitivity = 76%; specificity = 76%) and ß (sensitivity = 96%; specificity = 88%), from a single Scheimpflug image was found to be a successful tool to differentiate between keratoconus and control eyes with no misclassifications (sensitivity = 100%; specificity = 100%) with coefficients of variation up to 2.5%. Conclusions: The combination of microscopic and macroscopic corneal parameters extracted from a static Scheimpflug image is a promising, non-invasive tool to differentiate corneal diseases without the need to perform measurements based on induced deformation of the corneal structure. Translational Relevance: The proposed methodology has the potential to support clinicians in the detection of keratoconus, without compromising patient comfort.

Biomechanical Changes after in vivo Enzyme-Induced Corneal Crosslinking in Rabbits.

INTRODUCTION: Enzyme-induced corneal crosslinking (CXL) may be a promising and effective method to stiffen the cornea. However, there have been no reports on the effect of corneal CXL with enzyme in vivo. OBJECTIVE: To evaluate the biomechanical efficacy after in vivo enzyme-induced corneal CXL in rabbits using noninvasive imaging. METHODS: The eyes of 10 white New Zealand rabbits were unilaterally treated with CXL enzyme (transglutaminases [Tgases]). The contralateral eyes served as negative controls. In every rabbit, a 1 U/mL solution of Tgases was applied to the corneal surface. Corneal dynamic deformation by an air puff was measured using high-speed Scheimpflug imaging on day 14 after the procedure. Biomechanical parameters, central corneal thickness, and intraocular pressure were recorded and assessed. Then, corneal buttons were excised from euthanized animals for hematoxylin and eosin staining to evaluate changes in corneal collagen distribution and cell damage. RESULTS: Some biomechanical parameters showed statistically significant changes after in vivo CXL. The deformation amplitude and maximum corneal velocity during the second applanations were significantly lower than those of the untreated control group. The second applanations were significantly increased compared to the control group. No changes were found in other parameters. The morphology of the corneal stroma was similar in CXL-treated and untreated corneas. No obvious cell apoptosis was observed. CONCLUSIONS: Corneal stiffness increased after in vivo CXL induced by Tgases. This CXL method may be useful for corneal ectasia.

Effects of LASIK on Biomechanical Properties of Human Cornea / 医用生物力学

Objective To study the changes in biomechanical properties of human cornea after laser in situ keratomileusis (LASIK) and predict corneal stiffness after the LASIK surgery. Methods According to the measurement results from corneal visualization scheimpflug technology (Corvis ST), the corneal tangent stiffness coefficient (STSC) and energy absorbed area (Aabsorbed) were calculated. The change patterns of corneal stiffness and viscosity after refractive surgery were analyzed. Results The difference of corneal STSC and Aabsorbed before and after LASIK had a statistical significance (P<0.05). The obtained formula for predicting corneal stiffness after refractive surgery was: Sbefore surgery =1.055bIOPbefore surgery + 0.015CCTbefore surgery，Safter surgery =0.937Sbefore surgery +0.019CCTafter surgery. Conclusions LASIK surgery not only changes corneal thickness, but also reduces corneal stiffness and viscosity. Prediction of corneal stiffness after surgery can provide guidance for the design of clinical surgery and improve the safety of surgery.

[A comparative study of viscoelasticity between normal cornea and keratoconus].

Study of the mechanical properties of in vivo corneal materials is an important basis for further study of corneal physiological and pathological phenomena by means of finite element method. In this paper, the elastic coefficient ( E) and viscous coefficient ( η) of normal cornea and keratoconus under pulse pressure are calculated by using standard linear solid model with the data provided by corneal visualization scheimpflug technology. The results showed that there was a significant difference of E and η between normal cornea and keratoconus cornea ( P < 0.05). Receiver operating characteristic curve analysis showed that the area under curve (AUC) for E, η and their combined indicators were 0.776, 0.895 and 0.948, respectively, which indicated that keratoconus could be predicted by E and η. The results of this study may provide a reference for the early diagnosis of keratoconus and avoid the occurrence of keratoconus after operation, so it has a certain clinical value.

Evaluation of corneal elastic modulus based on Corneal Visualization Scheimpflug Technology.

BACKGROUND: Corneal biomechanical properties are important for the diagnosis of corneal diseases, individualized design and prognosis of corneal surgery. Clinical available devices such as Ocular Response Analyzer (ORA) and Corneal Visualization Scheimpflug Technology (Corvis ST) can provide corneal biomechanics related parameters, while corneal elastic modulus cannot be extracted directly from them at present. The aim of this study is to suggest a method to determine corneal elastic modulus based on the results of Corvis ST test according to Reissner's theory on the relation between stress and small displacement in shallow spherical shell. RESULTS: Five rabbits (10 eyes) and 10 healthy humans (20 eyes) were measured with Corvis ST to obtain the normal range of corneal elastic modulus. Results showed Corneal elastic modulus of rabbit was 0.16 MPa to 0.35 MPa, human corneal elastic modulus was 0.16-0.30 MPa. Rabbit corneas were also measured at different intraocular pressures (IOP), and results showed corneal elastic modulus, first applanation time (A1T) and stiffness parameter (SP-A1) were positively correlated with IOP. Deformation amplitude (DA), the second applanations time (A2T), and peak distance (PD) were negatively correlated with IOP. Finite element method was used to simulate the Corvis measurements according to the calculated elastic modulus and the simulated corneal apical displacements were agreement with experimental results in general. CONCLUSIONS: The method to determine corneal elastic modulus based on Corvis test according to the relationship between force and displacements of shallow spherical shell is convenient and effective.

A comparative study of viscoelasticity between normal cornea and keratoconus / 生物医学工程学杂志

Study of the mechanical properties of in vivo corneal materials is an important basis for further study of corneal physiological and pathological phenomena by means of finite element method. In this paper, the elastic coefficient ( ) and viscous coefficient ( ) of normal cornea and keratoconus under pulse pressure are calculated by using standard linear solid model with the data provided by corneal visualization scheimpflug technology. The results showed that there was a significant difference of and between normal cornea and keratoconus cornea ( < 0.05). Receiver operating characteristic curve analysis showed that the area under curve (AUC) for , and their combined indicators were 0.776, 0.895 and 0.948, respectively, which indicated that keratoconus could be predicted by and . The results of this study may provide a reference for the early diagnosis of keratoconus and avoid the occurrence of keratoconus after operation, so it has a certain clinical value.

Evaluation of the sensitivity and specificity of corneal visualization scheimpflug technology biomechanical index in the diagnosis of keratoconus / 中华实验眼科杂志

Objective To study the sensitivity and specificity of parameter Corvis biomechanical index (CBI)— a new biomechanical index of Corvis ST in the diagnosis of keratoconus and evaluate the role of CBI in the diagnosis of keratoconus and the change of biomechanic.Methods A diagnostic trial study was adopted,and 66 eyes from 49 keratoconic patients (keratoconus group) and 91 right eyes from 91 myopic patients (control group) from April in 2018 to August in 2018 in Henan Eye Hospital were enrolled.Pentacam and Corvis ST examinations were performed by the same operator after the basic eye examinations.Using the evaluation of diagnostic test,consistency test,and receiver operating characteristic (ROC) curve analysis,gain the outcome of the sensitivity,specificity,consistency,Youden index,and area under the ROC curve of the parameter CBI.This study protocol was approved by Ethic Committee of Henan Eye Hospital and followed the Declaration of Helsinki.Written informed consent was obtained from each patient prior to any medical examination.Results Sixty eyes were diagnosed as keratoconus by the parameter CBI of Corvis ST.Evaluation of diagnosis test:the sensitivity was 97.0％,and the specificity was 97.8％;consistency check:Kappa =0.948,P＜0.05.ROC curve analysis:the sensitivity was 98.5％,the specificity was 96.8％,Youden index was 96.3％,P＜0.000 1 and AUC was 0.996.Conclusions CBI can separate healthy eyes from keratoconic eyes with highly sensitivity and specificity,which was highly consistency with results of Rabinowitz keratoconus diagnostic criteria.CBI could be used as a new biomechanical indicator for the diagnosis of keratoconus.

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.