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G. Contraires, A. Curan, P. Dubois, J. F. Rouland; Biomechanical Properties of Human Cornea: Clinical Application in Penetrating Keratoplasty. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1763.
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The aim is to take part to the improvement of visual result in penetrating keratoplasty. We tried to understand mechanical behavior of human cornea with traction tests. Then, we gave an orientation to the graft to see consequences on final astigmatism.
3 Stages :- Orientation of the cornea right from the sample to obtain oriented specimens and oriented corneas.- Stage of the uniaxial traction tests on a Instron testing machine to obtain stress-strain relation on the oriented cornea standardized specimens. Cornea samples are oriented in 3 directions : Vertical, horizontal and oblique. We made rupture tests and cyclic tests.- Stage of oriented keratoplasty . 18 patients had an oriented graft at 90° or 180°. A comparative group had non oriented keratoplasty. We noted astigmatism and visual acuity 3, 6, and 12 years after penetrating keratoplasty.
- The mechanical study with stress strain tests confirms corneal anisotropy.For small deformation, cornea have a linear elastic behaviour. We can calculate Young modulus according to the different axis. Vertical (E= 0,25 MPa), horizontal (E=0,20 MPa) and oblique (E=0,125 MPa).- 3 months results of clinical study show that orientation of the graft during keratoplasty influence the values and the axis of astigmatisms. We also have a better visual acuity in the group with graft oriented at 90° (physiological position) than in the group with orientation at 180° or the group without orientation . We are waiting for 6 months and 12 months results.
We confirm corneal anisotropy. We observe that rigidity is predominantly vertical and then oblique and horizont. We can easly understand influence of graft orientation on the result of final astigmatism in penetrating keratoplasty.Graft orientation in penetrating keratoplasty could be interesting to improve final visual acuity.
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