Spatial heterogeneity of corneal biomechanical properties in myopia at nanoscale: A preliminary study

Purpose

To investigate the spatial heterogeneity of the corneal biomechanical properties in individuals with non-high and high myopia.

Methods

Atomic force microscopy was used to quantify the region-dependent elastic modulus (E) of 34 corneal lenticules from keratorefractive lenticule extraction surgery. The local E values of the central region, as well as the superior, inferior, nasal, and temporal points at the pericentral region, were measured. Differences between non-high myopia (−6.0 D < spherical equivalent [SE] ≤ −0.5 D) and high myopia (SE ≤ −6.0 D) were compared.

Results

E was significantly higher in the non-high myopia group than in the high myopia group (P < 0.0001). In non-high myopia, the central cornea exhibited a higher E than its pericentral counterpart (P < 0.0001), and the pericentral region E was higher in the horizontal direction than in the vertical direction (P = 0.0393). However, these values converged to be similar in high myopia (P = 0.5973, P = 0.7799). No significant differences in E were found between the superior and inferior pericentral corneas, nor between the nasal and temporal in both non-high (P = 0.0931, P = 0.1800) and high myopia (P = 0.5154, P = 0.1007). The E values of central and pericentral cornea were positively correlated with the mean radius of the posterior corneal surface (r = 0.3747, P = 0.0290; r = 0.3961, P = 0.0204).

Conclusion

In non-high myopia, region-dependent corneal biomechanics revealed higher stiffness centrally than pericentrally, with pericentral cornea stiffer horizontally than vertically. High myopia exhibited a reduced E and a gradual loss of spatial heterogeneity. Emphasizing spatial heterogeneity is crucial for a comprehensive understanding of the biomechanical behavior in myopia.