Polarimetric interferometry-derived isogyre parameters correlate with keratoconus severity: a retrospective observational study

Keratoconus involves progressive corneal thinning and stromal collagen disorganization that may precede conventional morphological detection. Polarimetric interferometry captures corneal birefringence related to collagen anisotropy and could serve as a non-invasive structural biomarker. We conducted a retrospective observational study of 95 keratoconus patients and 21 healthy controls who underwent corneal topography (Pentacam) and polarimetric interferometry (Lumaxis). Isogyre cross-pattern parameters, widest arm width, narrowest arm width, arm-width standard deviation, and centration indices (M1, M2), were quantified with GeoGebra and correlated with keratometric values, thinnest corneal thickness, Amsler-Krumeich staging, and Belin-Ambrosio ABCD classification. Widest arm width correlated strongly with Pentacam-derived AK stage (Spearman’s ρ = 0.798, p < 0.0001) and maximum keratometry (ρ = 0.730, p < 0.001), and moderately with thinnest corneal thickness (ρ = −0.488, p < 0.001). Arm-width asymmetry correlated inversely with thinnest corneal thickness (ρ = −0.381, p < 0.001). Receiver operating characteristic analysis showed promising discriminative performance: arm-width standard deviation (AUC 0.95) and widest arm (AUC 0.87) differentiated keratoconus from controls. Multivariable analyses confirmed independence from corneal curvature and thickness. Lumaxis-derived isogyre parameters correlate significantly with established keratoconus severity indices, supporting polarimetric interferometry as a complementary modality for assessing corneal stromal disorganization. Prospective longitudinal studies with automated image analysis are warranted.