Elastic properties of human posterior eye

Abstract

This study examines the elastic properties of the human posterior retina, choroid, and sclera. Twenty-four human eyes from 30- to 74-year-old donors were obtained from an eye bank. Vertically and horizontally oriented tissue strips of the retina, choroid, and sclera (ideally n = 12 in each group) were harvested from the posterior eyes. Their thicknesses were estimated optically. The samples were stretched at 1 mm/s in 37°C saline. Stress and strain were obtained from the mechanical tests, and then the transition stress, transition strain, toe modulus, and heel modulus were calculated. Statistical analysis was performed for comparison between groups. Linear regression analyses were used to explore the relationship between the mechanical parameters and age. We found that the stress-strain relationship of the retina, choroid, and sclera were nonlinear. Except for the retinal transition strain (p = 0.0124), no statistical difference was found between the vertical and horizontal meridian in the mechanical parameters (p > 0.05). Furthermore, weak relationship was observed between some of the mechanical parameters and the donors' age. Our results suggest that there is significant anisotropy in the retina, and mechanical properties of each layer may change with age.

Collagen Structure and Mechanical Properties of the Human Sclera: Analysis for the Effects of Age

“…Using biaxial experiments on human scleral strip specimens, Eilaghi et al [57] reported measures of stiffness between 0.5 MPa and 7.5 MPa. A recent uniaxial mechanical characterization of the sclera using uniaxial strip tests reported values of toe moduli vary ing between 1 kPa and 95 kPa, and heel moduli varying between 0.5 MPa and 13 MPa [58]. One could argue that the variability observed in those experiments cannot be compared to that observed in the present study because of the differences in experi mental protocol.…”

Predictions of Optic Nerve Traction Forces and Peripapillary Tissue Stresses Following Horizontal Eye Movements

“…30 This is likely to influence peripapillary tissue stresses and thus the potential development of peripapillary zones. Accordingly, we aimed to further investigate the sensitivity of ppBM stresses to variations in connective tissue stiffness.…”

A method to determine the mechanical properties of the retina based on an experiment in vivo

“…Although the mechanical properties of the retina are believed to be nonlinear by some researchers [13][14][15][16]18], a common understanding for the right constitutive model of the retina has not yet been reached. Mechanical properties of the retina are simplified as linear elasticity in most studies.…”

“…The choroid, lying between the retina and the sclera, is considerably stiffer than the retina and more resistant to mechanical deformation [12]. A classical approach to determine the mechanical properties is to perform a simple uniaxial test such as tensile or compression test, which involves significant simplifications and assumptions [6,7,11,[13][14][15][16][17][18]. The mechanical properties of porcine retinal tissue have been studied using tensile tests and the results show that Young's modulus was a factor 10 higher in the choroid compared with the retina [18].…”

“…The mechanical properties of porcine retinal tissue have been studied using tensile tests and the results show that Young's modulus was a factor 10 higher in the choroid compared with the retina [18]. Other works show that mechanical characteristics of the porcine retina are anisotropic and inhomogeneous [13][14][15]. The results of Chen et al show that the retina, choroid, and sclera behave nonlinearly, but only the retina exhibits surface anisotropy between the vertical and horizontal directions in body-temperature saline [14].…”