The methodology of digital image correlation of random white light speckle is applied to the measurement of strain in bovine retina tissue which is subjected to uniaxial tension loading.The digital image correlation compares an image of deformed "seeded" retinal tissue to an image of the same tissue in an undeformed state.The correlation of the deformed image with the undeformed image yields both the displacement and strain fields for the area of tissue which is being imaged.The "seeding" of the tissue is accomplished by randomly spreading micron sized steel spheres on the retinal tissue.The results of this study indicate that uniform strain fields are not obtained in simple tension tests of the non -homogeneous retinal tissue as one might assume in the mathematical modelling of such tests. The average strains in a center test section of the retinal strip are correlated and compared with the grip strains. In addition, the digital image correlation methodology is shown to have the capability to make predictions of strain in the proximity of blood vessels and other anomalies in the tissue.This feature of the digital imaging methodology yields valuable information concerning such problems as retinal tearing and separation.The mathematical and physical background of the digital image correlation methodology will be discussed. The limitations of this methodology to measure displacement and strain will be given.The experimental procedure which was used to test the bovine retina will be explained in detail and results from the uniaxial testing of this retina will be presented.
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