Below are 2 sets (or slides) of topographical ring and "point spread function images" (PSF) of the same pair of eyes of a patient that underwent both RK and LASIK surgery.
Although you can see the distorted ring images on the photos (slide) on top, what is most interesting are the "point spread function images" (PSF) that can be seen in the upper portions of both sets of images. Look carefully at both the upper and lower sets of PSF images. These images show how a very small beam of light "spreads" after passing through a pair post-surgical (LASIK) corneas and on the same corneas with scleral lenses (lower set of slides). The very small red dot represents a fine beam of light. In the upper set of images, note the white-grey "web-like" patterns around the red beam of light. This represents how light is "spread out" when passing through a distorted post-LASIK cornea. Note how the left PSF image (the image on the right side of the slide) is significantly more distorted than the right PSF image. This is because the left cornea is more distorted than the right cornea. This is why eyeglasses and soft contact lenses cannot provide the post-LASIK distorted cornea with clear, crisp vision. Note the PSF images of same pair of eyes with scleral lenses on the lower set of slides. Note that the small beam of light has virtually no distortion after passing through the scleral lenses. Also note that the ring images in the lower half of the bottom set of slides are perfectly round. Note how the topographical rings in the lower half of the upper set of slides are significantly distorted. Scleral lenses in effect replace the cornea as an optical surface.