A biphasic biomechanical model of the cornea with concentration effects

M. R. Bryant, P. J. McDonnell

Research output: Contribution to journalArticlepeer-review


Purpose. To develop a biomechanica model of the cornea that includes fluid and solid material behaviors, ion concentration effects, and their mutual interactions. Methods. A modified biphasic formulation for the steady-state biomechanical behavior of the cornea was developed from mixture theory. The corneal stroma was considered to be a two-phase mixture of solid and fluid, with a distribution of negative charges (associated with the negative charge groups of the proteoglycans) fixed to the solid phase but acting as part of the fluid phase. The momentum equations for each phase were augmented with body force terms accounting for the concentration of free ions in the stroma. The equilibrium distribution of free ions was determined by requiring that gradients of the electrochemical potentials were zero at equilibrium, subject to the constraint of bulk charge electroneutrality of the free ions with the fixed negative charges of the stroma. Using a transversely isotropic constitutive assumption for the solid phase, the confined compression experiments of Hedbys and Dohlman (Exp Eye Res 1963;2:122-129) were simulated. Results. The swelling pressure-hydration response of the cornea measured by Hedbys and Dohlman was well represented by the model using the following solid phase material properties: inplane elastic modulus, 0.49 N/mm2; transverse modulus, 3.55e-5 N/mm2; inplane Poissons ratio, 0.49; transverse Poissons ratio, 0.0. Conclusions. The model accounts for the interaction of biomechanical stresses in the stroma with changes in stromal hydration and may provide new insights into the biomechanics of refractive surgery.

Original languageEnglish (US)
Pages (from-to)S69
JournalInvestigative Ophthalmology and Visual Science
Issue number3
StatePublished - Feb 15 1996
Externally publishedYes

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience


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