Longitudinal biomechanical changes and progression-associated parameters in subclinical keratoconus: a prospective study

In this longitudinal study, we assessed biomechanical changes in eyes with subclinical keratoconus (SKC) and explored features associated with progression. A total of 283 patients were included. The mean follow-up was 24.8 ± 13.7 months and the longest follow-up was 76 months. Biomechanical parameters were obtained using the Corvis ST (OCULUS Optikgeräte GmbH, Wetzlar, Germany), and tomographic data with the Pentacam (OCULUS Optikgeräte GmbH, Wetzlar, Germany). Longitudinal trends were visualized with line plots, and linear mixed-effects models were used to evaluate longitudinal changes in biomechanical parameters over time. Receiver operating characteristic (ROC) analysis and univariable logistic regression were used to explore biomechanical parameters associated with progression. Of all SKC eyes, 24.4% demonstrated progression during follow-up. Biomechanical parameters showed greater variability than morphological parameters. Linear mixed-effects models showed significant longitudinal changes and significant progression × time interactions for CBI, TBI, SP-A1, DA Ratio Max (2 mm), and E-staging (all p < 0.05). DA Ratio Max (2 mm) showed the highest discriminative performance for progression (AUROC = 0.882), followed by CBI and TBI (AUROC = 0.813, 0.787, respectively). In univariable logistic regression analyses, higher TBI (OR = 1.499, 95% CI: 1.124–1.998; p = 0.006), CBI (OR = 1.503, 95% CI: 1.120–2.016; p = 0.007), and DA Ratio Max (2 mm) (OR = 1.362, 95% CI: 1.124–1.650; p = 0.002) were significantly associated with higher odds of progression. SKC eyes exhibited significant longitudinal biomechanical alterations. CBI, TBI, SP-A1, DA Ratio Max (2 mm), and E-staging showed differences between the progression and non-progression groups over time, while higher TBI, CBI, and DA Ratio Max (2 mm) were associated with progression. These findings suggest that biomechanical parameters may provide more useful information for characterizing early changes in SKC.