A novel metric to monitor early progression in keratoconus: epithelial backscatter

To assess the keratoconus progression over the course of one-year using epithelial and anterior stromal backscatter, Belin ABCD progression display, and various Pentacam^® parameters and to determine whether backscatter measurements can be utilized to monitor progression.

This single-centre, retrospective, longitudinal, observational study evaluated change in epithelial and anterior stromal backscatter (using the line densitometry feature of the Pentacam^®) and the flat, steep, mean and maximum keratometry, Belin ABCD progression display, corneal elevations, Belin/Ambrósio enhanced ectasia display (BAD-D), pachymetric progression index (PPI), maximum Ambrósio relational thickness (ARTmax), and topometric indices, between baseline and one-year in 37 eyes (37 patients) with keratoconus.

When compared to the baseline after one-year, epithelial backscatter increased (p < 0.05); posterior radius of curvature, BAD-D, average PPI, index of vertical asymmetry (IVA), and index of height decentration (IHD) worsened (p < 0.05); and the anterior stromal backscatter, keratometry values, Belin ABCD stages, thinnest pachymetry, elevations, and ARTmax remained stable (p > 0.05). There were statistically significant weak-to-moderate correlations between the backscatter values and Pentacam^® parameters (p < 0.05).

Epithelial backscatter can be considered a novel parameter to monitor the progression of keratoconus, as it was found to have similar abilities to those of the posterior radius of curvature, BAD-D, average PPI, IVA, and IHD, all of which demonstrated early evolution during one-year of follow-up, while the front keratometric data exhibited no progression. Moreover, by generalizing single-point backscatter data to the entire corneal surface, epithelial backscatter can be integrated into Pentacam^® maps as a novel feature in keratoconus diagnosis and progression follow-up.