A method for measuring an optical system comprises transmitting an image with the optical system. Gradients of the optical system can be determined by separating the transmitted image with a lenslet array. An error-correcting change in the shape of the optical system can be mapped by integrating across the gradients. The change in elevation around the path is related to the accuracy of the gradient array. A system for measuring a wavefront of an eye includes an image source for projecting an image into the eye, lenslets, a detector for measuring angles of light rays of an optical surface of an eye, and a computer for mapping the errors of the eye. A tomographic wavefront map is made by deflecting the measurement path of the wavefront sensor. Aberrations are selected for treatment in response to an order of the aberration and a tissue structure corresponding to the aberration.