Drained secant modulus for human and porcine peripapillary sclera using unconfined compression testing

Area of Science:

• Ocular Biomechanics
• Biomaterials Science
• Ophthalmology

Background:

• Glaucoma involves optic nerve head damage, potentially linked to scleral material properties.
• Previous research focused on scleral tensile behavior, neglecting its compressive stiffness.
• Understanding scleral compressive properties is crucial for biomechanical models of the optic nerve head.

Purpose of the Study:

• To characterize the compressive moduli of human and porcine peripapillary sclera.
• To investigate the effect of strain and age on scleral compressive behavior.
• To provide data for computational simulations of ocular tissues and glaucoma mechanisms.

Main Methods:

• Unconfined compression (UCC) tests were performed on human and porcine scleral samples.
• UCC stress-relaxation tests were conducted at sequential compressive strains (5%, 10%, 15%).
• Drained equilibrium stress and drained secant modulus were calculated.

Main Results:

• Human scleral drained equilibrium stress decreased linearly with age in males (79.4 Pa at 78 yrs to 40.1 Pa at 89 yrs).
• Drained secant modulus (E(5)) was 1.1 ± 0.08 kPa for human and 3.9 ± 0.57 kPa for porcine sclera.
• Drained equilibrium stress increased non-linearly with increasing compressive strain.

Conclusions:

• Scleral compressive stiffness data offer insights into peripapillary tissue mechanics.
• Age-related changes in scleral biomechanics may contribute to glaucoma's increasing prevalence.
• Findings support the development of advanced computational models for optic nerve head biomechanics.