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Jourdan Colter, nathaniel cady, Brenda Mann, Barbara M Wirostko, Brittany Coats; Finite-element design of a carboxymethylated hyaluronic acid (CMHA-S) ocular bandage. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1976. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Novel CMHA-S provides a unique platform for ocular bandages designed to protect and promote healing of the corneal surface following battlefield injuries as they can be molded into any design. To date, it is unknown what geometric features, material properties, and sizing is required to immobilize a CMHA-S bandage on the eye, and withstand physiological forces. The goal of this numerical study was to use finite-element (FE) analysis to (1) compare conceptual versions of the CMHA-S ocular bandages for retention, (2) determine the extent to which these bandages fit a range of corneal sizes; and (3) parametrically evaluate the effects of elastic modulus and thickness on retention.
A CMHA-S bandage was modeled on a simplified eye consisting of a cornea and upper/lower eyelids. A sursumduction eye movement was applied, and the relative displacement between the bandage and cornea was measured. Eight versions of the bandage were tested in the model. The final selected version was evaluated on corneal sizes two standard deviations above and below the mean. Model simulations iterated the bandage’s elastic modulus between ±94% of the current modulus, and iterated thickness 2–7 times the original.
Bandages with internal surfaces molded to the shape of the cornea yielded relative displacements 66% lower than those forming a concave bridge around the cornea. Simulations with smaller corneas produced relative displacements very similar to average-sized corneas (0.01 mm difference), while simulations with larger corneas resulted in much greater relative displacements (>113% difference). Increasing elastic modulus of CMHA-S decreased the relative displacement between the bandage and the cornea; however, elastic moduli greater than the CMHA-S current modulus negligibly affected bandage displacement (< 0.05 mm). Bandage thickness did not greatly affect its displacement, in which all thickness iterations yielded relative displacements less than 0.05 mm.
Model outputs determined CMHA-S ocular bandages will perform best if molded to a larger than average size cornea. No modification to the current material properties of CMHA-S is needed. There is considerable flexibility in the allowable thickness of the bandage. This will be useful in accommodating drug-loading requirements, improve ease of handling, and relax thickness tolerances during manufacturing.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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