An apparatus and method for measuring mechanical properties of tissue has a stereo optical surgical microscope with at least one objective lens and at least two digital cameras such that paired images obtained from the digital cameras form stereo pairs, and a digital image processing system adapted to determine surface topography of tissue from the stereo pairs of images and a resulting surface displacement map as a result from indentation. The apparatus has an one indenter; and mechanical modeling routines stored in memory of the image processing system, the mechanical modeling routines capable of constructing computer models of mechanical properties of tissue, and fitting parameters of the computer model to observed surface displacement maps generated by coregistering surface topography of tissue with and without the indenter positioned on the tissue. In an embodiment, fitted parameters of the computer model are displayed and used to adjust a surgical plan. An apparatus and method for measuring mechanical properties of tissue has a stereo optical surgical microscope with at least one objective lens and at least two digital cameras such that paired images obtained from the digital cameras form stereo pairs, and a digital image processing system adapted to determine surface topography of tissue from the stereo pairs of images and a resulting surface displacement map as a result from indentation. The apparatus has an one indenter; and mechanical modeling routines stored in memory of the image processing system, the mechanical modeling routines capable of constructing computer models of mechanical properties of tissue, and fitting parameters of the computer model to observed surface displacement maps generated by coregistering surface topography of tissue with and without the indenter positioned on the tissue. In an embodiment, fitted parameters of the computer model are displayed and used to adjust a surgical plan.