Scleral shape and its correlation with corneal parameters in keratoconus.

Purpose: To assess the correlation of the scleral shape and corneal tomographic parameters in keratoconus.

Methods: Twenty eyes of 15 keratoconus patients with no previous specialty lens wear or ocular surgery were included in this study. Corneal imaging was obtained with the Pentacam HR and three-dimensional (3D) corneoscleral maps were acquired using the Eye Surface Profiler, ESP. Sagittal height was calculated at the central corneal level (annulus of 0-4 mm radius), peripheral cornea (annulus 4-6 mm radius) and sclera (annulus 6-8 mm radius) using ESP maps and Pentacam HR (exclusively for the central cornea). The flattest and steepest regions of each annulus and the circumferential scleral asymmetry were calculated based on custom-made software. The Pearson correlation coefficient (r) was used to evaluate the correlation between corneal parameters as measured by Pentacam HR and scleral asymmetry.

Results: Anterior corneal parameters, such as flattest and steepest keratometry, were found to be correlated with scleral asymmetry in keratoconus (all r>0.5, p < 0.05). In contrast, anterior astigmatism showed poor correlation with the level of scleral irregularity (r=-0.11; p = 0.32). Other disease-specific parameters pertaining to the posterior corneal curvature and corneal thickness were not correlated with scleral asymmetry. The steepest regions of the central cornea, peripheral cornea, and sclera tended to share a common angle (r = 0.92; p < 0.001 for central cornea compared to sclera).

Conclusion: Anterior corneal parameters measured by corneal imaging are associated with the level of scleral asymmetry and the orientation of the steepest area of the sclera in eyes with keratoconus.