Relationship of Change in Biomechanical Properties of Ocular Rigidity After Laser Anterior Ciliary Procedure to Accommodative Function
Purpose
To measure the baseline material properties of porcine and human scleral tissue in order to correlate the laser ablations with a change in the biomechanical properties of the sclera at various stages of ocular rigidity relative to accommodative function.
Methods
Tensile tests were conducted to determine the average elastic modulus in porcine and human scleral tissue. Human samples included sclera tissue of young and old patients in various age groups: 45-50;51-55;56-60 within 24 hours postmortem varying in ocular rigidity. Elastic modulus was measured with stress-strain tests in the circumferential and longitudinal direction. Strips were subjected to a constant strain rate to measure force. Stress-strain curves were generated and analyzed to determine the elastic modulus. LaserACE microablations at various depths were made and compared to baseline data. Ultimate stress, ultimate strain and Young's modulus at 10% strain were used for analysis.
Results
Stress-strain curves were generated and analyzed to determine the elastic modulus. Scleral stiffness was relatively low between 5 mmHg and 10 mmHg, and elastic modulus varied with age. Data and model were validated statistically and baseline data created. Similar stress strain curves were generated for LaserACE treatment groups at various ages. Material property changes related to the treatment are presented.
Conclusion
Stress-strain curves and elastic modulus indicate biomechanics of the sclera vary with age. Biomechanical models based upon the results may be useful to investigate scleral procedures aimed at altering ocular rigidity. FEA is important for more comprehensive investigation of the relationship between ocular rigidity and accommodation efficiency. Techniques such as the LaserACE procedure which aim to reduce ocular rigidity may improve accommodation efficiency through biomechanical property modification.
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