An apparatus for measuring a subject's eye having an instrument axis, comprising a slit projector for projecting slits of light, at least one sensor. The apparatus being adapted to form a first image of light from a first slit on the at least one sensor after the light scatters from the eye along a first pathway. The apparatus adapted to form a second image of light from the first slit on the at least one sensor after the light scatters from the eye along a second pathway. The apparatus comprising a processor operatively coupled to receive the first image and the second image, the processor adapted to perform a projective transformation of the second image and to combine data from the first image and the second image, after it is transformed, to form a third image.