A system measures a corneal topography of an eye. The system includes a group of first light sources arranged around a central axis, the group being separated from the axis by a radial distance defining an aperture in the group； a plurality of second light sources； a detector array； and an optical system adapted to provide light from the second light sources through the aperture to a cornea of an eye, and to provide images of the first light sources and images of the second light sources from the cornea, through the aperture, to the detector array. The optical system includes an optical element having a focal length,/ The second light sources are disposed to be in an optical path approximately one focal length,/ away from the optical element
