An Exploratory Analysis of Forme Fruste Keratoconus Sensitivity Diagnostic Parameters

Abstract Purpose: To re-statistical analysis of the Pentacam or Corvis ST parameters from literatures, and to obtain more sensitive diagnostic parameters for clinical keratoconus (CKC) and forme fruste keratoconus (FFKC), respectively. Methods: The parameters and the corresponding area of ROC curve (AUC) in previous studies were extracted and screened to obtain the database of CKC (Data-CKC) and FFKC (Data-FFKC), respectively. Two different importance evaluation methods (%IncMSE and IncNodePurity) of random forest were used to preliminary select the important parameters. Then, based on the partial dependency analysis, the sensitive diagnostic parameters that had promotion to the diagnostic performance were obtained. Data-FFKC was analyzed in the same way. Finally, a diagnostic test meta-analysis on the sensitive parameter of interest was conducted to verify the reliability of the above analysis methods.Results: There were 88 parameters with 766 records in Data-CKC, 57 parameters with 346 records in Data-FFKC. Based on two importance evaluation methods, 60 important parameters were obtained, of which 20 were further screened as sensitive parameters of keratoconus, and most of these parameters were related to the thinnest point of cornea. The stiffness parameter at first applanation (SPA1) was the only Corvis ST output parameter sensitive to FFKC except the Tomographic and Biomechanical Index (TBI) and the Corvis Biomechanical Parameter (CBI). A total of 4 records were included in the meta-analysis of diagnostic tests on SPA1. The results showed that there was threshold effect, but no significant heterogeneity (I2=33%), and the area under the SROC curve was 0.87 (95% CI, 0.84-0.90).Conclusions: the sensitive diagnostic parameters of keratoconus mainly include the 7 categories. The diagnostic value of SPA1, which represents the biomechanical properties of cornea, is worthy of further attention in the diagnosis of keratoconus in forme fruste keratoconus. Moreover, the morphological parameters based on the typical position of the thinnest point of corneal thickness have potential special significance for the diagnosis of disease.