Animal basement membranes are networks of laminin, type IV collagen and other proteins essential for physiological functions. Deficiencies or abnormalities in the proteins can lead to muscular dystrophy, kidney disease, hearing loss, and, in the extreme, embryonic demise. In an effort to determine how the complex structure determines the functional properties of the basement membrane, the change in mechanical behavior is being investigated on samples with defective or absent associative proteins as compared to those with intact matrix components. A test was developed using the mouse model to take advantage of the genetic control possible in the mouse. The ocular lens capsule is a basement membrane which is large and thick, relative to others in the body, and which can be studied without major disruption. The lens is extracted from the eye and subjected to osmotic swelling, requiring minimal dissection and manipulation. The change in radius over time is evaluated with a mathematical model recently developed using porcine lenses to determine the elasticity of the capsule. Currently, data are being collected and analyzed to determine the elasticity of the normal mouse ocular lens capsule, which will serve as the control for future studies on mice with genetically-determined basement membrane modifications.