Extensibility of the normo-hydrated human cornea.

The extensibility of 10 human corneas was evaluated in vitro by measuring central epithelial side and endothelial side tangential strain induced by intraocular pressure loads ranging from 2 to 100 mmHg. Corneal normo-hydration was attempted by immersing and perfusing the eyes with 8% Dextran 500 in isotonic saline. The relationship between corneal strain and intraocular pressure was found to be non-linear, showing a typical stress-stiffening behaviour. Strain changes were approximately 10% higher on the endothelial side compared with the epithelial side. This difference could be fully explained by pressure induced changes in corneal volume. Compared to previous experiments performed on swollen corneas, the stiffness of the normo-hydrated human cornea was found to be higher. Young's modulus of elasticity for the corneal stroma was estimated to 3, 9, and 20 MPa for intraocular pressure intervals of 2-10, 10-25, and 25-100 mmHg, respectively.

[1]  T. Olsen,et al.  The swelling pressure of the human corneal stroma as determined by a new method. , 1987, Experimental eye research.

[2]  W. A. Schlegel,et al.  Nonlinear material properties of intact cornea and sclera. , 1972, Experimental eye research.

[3]  K. Buzard.  Introduction to biomechanics of the cornea. , 1992, Refractive & corneal surgery.

[4]  D. Maurice,et al.  The mechanical properties of the rabbit and human cornea. , 1986, Journal of biomechanics.

[5]  D. Poinoosawmy,et al.  Variations in visual acuity, refraction, and corneal curvature with changes in applanation tension. , 1974, The British journal of ophthalmology.

[6]  Y. Fung,et al.  Biomechanics: Mechanical Properties of Living Tissues , 1981 .

[7]  G O Waring,et al.  Computer simulation of arcuate keratotomy for astigmatism. , 1992, Refractive & corneal surgery.

[8]  G O Waring,et al.  Preliminary computer simulation of the effects of radial keratotomy. , 1989, Archives of ophthalmology.

[9]  P. Pinsky,et al.  A microstructurally-based finite element model of the incised human cornea. , 1991, Journal of biomechanics.

[10]  D. Hoeltzel,et al.  Strip Extensiometry for Comparison of the Mechanical Response of Bovine, Rabbit, and Human Corneas , 1992 .

[11]  P. Kiely,et al.  Diurnal Variations of Corneal Topography and Thickness , 1982, American journal of optometry and physiological optics.

[12]  P R Greene,et al.  Comparison of mechanical properties of keratoconus and normal corneas. , 1982, Experimental eye research.

[13]  H. Oxlund,et al.  Biomechanical properties of keratoconus and normal corneas. , 1980, Experimental eye research.

[14]  R P Vito,et al.  Finite element based mechanical models of the cornea for pressure and indenter loading. , 1992, Refractive & corneal surgery.

[15]  P. K. Jensen,et al.  In vitro measurement of corneal strain, thickness, and curvature using digital image processing. , 2009, Acta ophthalmologica Scandinavica.

[16]  Erik Sjøntoft,et al.  In vivo determination of young's modulus for the human cornea , 1987, Bulletin of mathematical biology.

[17]  Hansen Fk.  A clinical study of the normal human central corneal thickness. , 1971 .