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Editors Selection IGR 13-3
Basic Research - Sclera: Biomechanical properties
Comment by Jonathan Vande Geest on:
46435 Biomechanical Changes in the Sclera of Monkey Eyes Exposed to Chronic IOP Elevations, Girard MJ; Suh JK; Bottlang M et al., Investigative Ophthalmology and Visual Science, 2011; 52: 5656-5669
What is the role of the biomechanical and structural properties of posterior ocular tissues in glaucoma? Is it causative? Correlative? Associative? Predictive? These questions are starting to be more thoroughly investigated by many researchers in the field of ocular biomechanics. In this work, Girard et al. (1151) set out to identify changes in the biomechanical properties of the posterior peripheral and peripapillary monkey sclera in response to elevated intraocular pressure (IOP). Experimental glaucoma (EG) was induced via laser treatment in eight monkeys, using a contralateral eye in each monkey as a normal control. Pressure inflation of each posterior scleral shell was performed, using a speckle interferometry technique to map heterogeneous scleral displacements. Inverse finite element modeling was then used to determine the values of the constitutive model parameters in a nonlinear, anisotropic, hyperelastic, and heterogeneous biomechanical model for the sclera. The authors then compare values of tangent modulus (an IOP-dependent measure of material stiffness) and a structural stiffness measure (which includes scleral thickness) across all eyes.
Remodeling occurs in the posterior sclera in response to elevated IOP
The authors found that five out of the eight EG monkey eyes exhibited some form of change in either the material or the structural stiffness of the sclera. While these changes were not consistent across all eyes, the general conclusion of the work is that EG eyes displayed increased stiffness, especially at higher IOP, than their contralateral control. The authors also found a non-significant trend towards scleral thinning in the EG eyes. This paper is perhaps one of the first to establish, using a well-controlled experimental model of glaucoma, that remodeling occurs in the posterior sclera in response to elevated IOP. Given that the role of the peripapillary sclera in protecting the lamina cribrosa has already been established, this work provides an important experimental link between scleral remodeling and potential glaucomatous damage. As a result, the authors have laid the groundwork for future investigations focusing on further elucidating the role of these tissues in the onset and progression of glaucoma.
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