ABSTRACT
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.
ABSTRACT
Objective@#To evaluate the repeatability of corneal biomechanics parameters measured by Corneal Visualization Scheimpflug Technology (Corvis ST) and explore the factors that influence the repeatability.@*Methods@#A diagnostic test study was performed.A total of 190 eyes in 95 myopia patients (34 males and 61 females) were enrolled from September to October 2017 in Henan Eye Hospital.All the subjects underwent 5 repeated examinations with the Corvis ST.The intraclass correlation coefficient (ICC), Cronbach α coefficients and repeatability coefficient (RC) were computed to evaluate repeatability of Corvis ST parameters.The multiple linear regression analysis was used to study the factors that affect the magnitude of the test-retest variability (within subject SD) of new Corvis ST parameters.This study was approved by the Ethics Committee of Henan Eye Hospital (HNEECKY-2019[5]), and written informed consent was obtained from each subject.@*Results@#Among the 39 biomechanics parameters, The ICC and Cronbach α were greater than 0.75 for 26 parameters, within 0.60-0.75 for 4 parameters, and lower than 0.60 for deflection amplitude max time (DLAMT). The ICC and Cronbach α of DA ratio max[1 mm], DA ratio max [2 mm], max inverse radius, Ambrósio's relational thickness horizontal (ARTh), biomechanical intraocular pressure (bIOP), integrated radius, stiffness parameter applanation 1 (SPA1) and Corvis biomechanical index (CBI)were all above 0.920.The multivariate regression results indicated that the within subject SD of bIOP increased with the increase of IOP (β=0.210, P=0.010). The within subjects SD of DA Ratio Max [1 mm]decreased with the increase of central corneal thickness (CCT) (β=-0.218, P=0.008). The within subjects SD of DA Ratio Max [2 mm]decreased with the increase of CCT(β=-0.295, P<0.001). The within subject SD of CBI decreased with the increase of astigmatism, axial lengths and CCT (β=-0.190、-0.148、-0.428, all P<0.05).@*Conclusion@#The Corvis ST parameters showed favorable measurement repeatability in myopia patients, especially for the new parameters.Astigmatism, axial lengths and CCT significantly affected the repeatability of CBI.
