Is keratoconus limited to the cornea? A prospective analysis of corneal biomechanics using corneal visualisation Scheimpflug technology.

PURPOSE

This study aimed to evaluate whether corneal biomechanical alterations in keratoconus (KC) are associated with changes in the lamina cribrosa (LC), retinal nerve fibre layer (RNFL) and peripapillary microvascular structures by comparing these parameters with healthy controls.

METHODS

In this prospective, cross-sectional, case-control study, 66 eyes of 66 KC patients and 76 eyes of 76 healthy controls were enrolled. Corneal morphological and biomechanical parameters were measured using Scheimpflug imaging (Pentacam) and a dynamic Scheimpflug analyser (Corvis ST). Posterior segment structures were evaluated using swept-source optical coherence tomography (SS-OCT) and OCT angiography (SS-OCTA). The radial peripapillary capillary plexus (RPCP) density, RNFL thickness and LC parameters (lamina cribrosa thickness [LCT] and lamina cribrosa curvature index [LCCI]) were measured. The relationship between corneal biomechanical parameters and structural changes in the LC was evaluated by correlation analysis.

RESULTS

Biomechanical parameters were significantly poorer in the KC group compared to controls. RNFL thickness and RPCP density were significantly lower in KC patients (p < 0.05). LCT was significantly lower, whereas LCCI was significantly higher in KC patients compared with controls (p < 0.001 for both). Significant correlations were observed between LCT and minimum central corneal thickness (r = 0.26, p = 0.04) and maximum keratometry (r = -0.28, p = 0.03). However, no significant correlations existed between LCCI and biomechanical parameters.

CONCLUSION

This study suggests that corneal biomechanical changes in KC are associated with structural alterations in the LC, indicating that KC may not be limited to the cornea alone, but may be related to broader ocular collagen involvement.