Is Keratoconus More Than Just a Corneal Disease?

Purpose: The aims of this study were to compare the scleral thickness (ST), lamina cribrosa thickness (LCT), and lamina cribrosa curvature index between patients with keratoconus and healthy controls and to evaluate the relationship between these values and corneal parameters. Methods: This cross-sectional study included 41 eyes of 41 patients with keratoconus and 30 eyes of 30 age-matched, sex-matched, and axial length-matched controls. Nasal and temporal STs were measured vertically, 4 mm posterior to the scleral spur, using anterior segment optical coherence tomography. The LCT was measured on the radial scans of the optic nerve head. The lamina cribrosa curvature index (lamina cribrosa curvature depth/curvature width x 100) was calculated to determine the degree of posterior bowing of the lamina cribrosa. Results: The nasal ST and temporal ST were significantly lower in the keratoconus group than in the control group (P = 0.016 and P = 0.023, respectively). The LCT was significantly lower in the keratoconus group compared with the control group (P < 0.001). There was no significant difference between the groups for the lamina cribrosa curvature index (P = 0.375). Correlation analysis revealed a significant correlation between the nasal and temporal STs and the central corneal thickness (r = 0.376, P < 0.001 and r = 0.387, P < 0.001, respectively). There was also a significant correlation between the temporal ST and the minimum corneal thickness in the keratoconus group (r = 0.332, P = 0.015). The LCT was significantly correlated with the central corneal thickness (r = 0.445, P < 0.001). Conclusions: Structural features of the cornea, sclera, and lamina cribrosa with similar collagen content may be similarly affected in patients with keratoconus. Further histologic studies are needed to confirm our results.