Apparatus for determining if a
cornea (whether
in vitro or
in vivo) has been modified (either surgically or otherwise). The method includes the steps of: passing a beam of
collimated light a (either coherent or incoherent) through the
cornea to produce a distorted
wavefront; determining the characteristics of the distorted
wavefront; and analyzing the distorted
wavefront for characteristics that identify the presence of a modification. The analysis of the distorted wavefront can be for the presence of higher order aberrations, or Gausian characteristics which are indicative of modifications. More particularly, the method includes the steps of providing an optical
system that has a
pupil plane and an
image plane at a
detector; positioning the
cornea in the
pupil plane; passing a collimated beam of light through the cornea to produce at least two images in the
image plane; determining the characteristics of the distorted wavefront; and analyzing the distorted wavefront for characteristics that identify the presence of a modification. The apparatus includes: a source of
collimated light: an optical
system including a distorted
grating and an
imaging lens (which have a
pupil plane, first and second virtual planes, and an
image plane); structure for positioning the cornea in the pupil plane; and a computer. The structure for positioning the cornea (which is immersed in a suitable storage fluid) includes first and second plano / plano lenses. The first and second plano lens, which are substantially and perpendicular to and centered with respect to the axis, have less than λ / 10 total distortions.