Combined corneal biomechanical and tomographical indices in subclinical and forme fruste keratoconus

Abstract

Abstract Purpose: Evaluation of combined corneal tomographic and biomechanical parameters in subclinical/forme fruste keratoconus (ScKC/FFKC). Design: Cross-sectional observational case-control study Methods: Inclusion criteria: 31 eyes with ScKC (fellow eye of KC with any one sign: keratometry >47 diopters, cylinder >1.5D, central corneal thickness <500mm, with/without abnormal topography) or FFKC (fellow eye of KC with normal topography and slit lamp examination) >13 years (cases) and 44 eyes of age-matched 22 healthy subjects (controls). Exclusion criteria:Clinically diagnosed KC, presence of corneal scars, prior ocular surgery eyes. Study parameters:16 Pentacam, 15 Corvis ST and 5 Sirius parameters were analysed using paired sample t-test and sub-sample found to be significantly different was used in ROC analysis. Youden Index was calculated and Pearson’s correlation analysis was done. Results: 5 Pentacam, 3 Corvis ST and 2 Sirius parameters had AUC >0.75. TBI (cut-off 0.59, 95% specificity, 77% sensitivity), BAD (cut-off 1.8, 81% specificity, 80% sensitivity) and SIb (cut-off 0.16, 97% specificity, 67% sensitivity) best identified early KC. TBI strongly correlated with maximum Pentacam parameters in both cases and controls. CBI strongly correlated only in cases and SP-A1-SD weakly correlated in cases. Conclusion: Upon combined analysis, average sensitivity and specificity respectively of top three parameters (according to AUC) from Pentacam and Corvis ST was 74.1% and 95.4% for PE and TBI, 81.3% and 78.1% for BAD and SP-A1-SD and 77.1% and 82.9% for KI and CBI. Average sensitivity and specificity respectively of top two parameters (according to AUC) from Sirius was 66.1% and 97.6% for SIb and BCVb. Trial Registration: Trial registered in Clinical Trial Registry of India on Jan 28, 2022. Trial Registration Number is REF/2022/01/050638.