Role of corneal epithelial mapping, Corvis biomechanical index, and artificial intelligence-based tomographic biomechanical index in diagnosing spectrum of keratoconus.

Abstract

The aim of the study was to evaluate the utility of epithelial mapping, Corvis biomechanical index (CBI), and tomographic biomechanical index (TBI) in diagnosing the spectrum of keratoconus (KC). This was a retrospective study where KC subjects with an age between 11 and 50 years were enrolled. Subjects with ocular diseases, history of previous corneal surgery, corneal scars or hydrops, ocular trauma, ocular surface disorder, systemic disease, and poor-quality scans were excluded. KC was classified using Belin ABCD classification system. Epithelial thickness, corneal tomography, and corneal biomechanical measurements were recorded using Fourier-domain optical coherence tomography Avanti with corneal adaptor module, Pentacam HR, and Corvis® ST, respectively. To understand the utility of various corneal parameters in diagnosing spectrum of keratoconus, cutoff values for epithelial thickness at the thinnest location and its standard deviation (SD) were considered 45 and 3 microns, respectively, CBI of 0.5 and TBI of 0.29 was considered. Sixty-five eyes (45 - KC, 10 - subclinical KC (SBKC), and 10 - forme fruste [FF]) of 34 patients with a mean ± SD age of 30.73 ± 5.71 were included. In our keratoconic sample, epithelial mapping alone helped diagnose the 77.77% of cases, however, when combined with CBI, it helped diagnose 95.5% cases and when combined with TBI, it was useful in diagnosing 100% of cases. In SBKC group, 40% of cases were detected by epithelial mapping alone, and when combined with CBI, it helped diagnose 70% of cases and TBI further helped diagnose 90% of cases. We did not see any role of epithelial mapping in detecting FFKC cases whereas CBI and TBI helped diagnose 60% and 90% of cases, respectively. The utility of epithelial mapping as a solitary tool is limited in detecting the spectrum of KC, especially SB and FFKC. However, combining it with corneal biomechanical parameters could help improve the efficacy of diagnosis of KC.