The ocular lens stifiens dramatically with age, resulting in a loss of function. However, the mechanism of stifiening remains unknown, at least in part due to di±culties in making reliable measurements of the intrinsic mechanical properties of the lens. Recent experiments have employed manual compression testing to evaluate the stifiness of murine lenses which have genotypes pertinent to human lens diseases. These experiments compare the extrinsic stifiness of lenses from the genotype of interest to the wild-type lens in an efiort to reach conclusions regarding the cellular or molecular basis of lens stifiening. However, these comparisons are confounded by alterations in lens size and geometry which invariably accompany these genetic manipulations. Here, we utilize manual lens compression to characterize the stifiness of a porcine lens and a murine lens. An inverse elastographic technique was then developed to estimate the intrinsic shear modulus of each lens as well as the elastic modulus of the lens capsule. The results were in good agreement with the previous literature values.