This diagram shows the curvature of the cornea, the outermost layer of the eyeball. When light hits the cornea, it bends to focus on the retina, the inner layer of the eye.
All corneas are individual and the center is steeper (more convex) that the periphery. This printout helps the doctors to most accurately fit contact lenses.
Both Lasik surgery and CRT Contact Lenses flatten the central steep portion of the cornea thereby eliminating myopia.
In this case, the steepness of the cornea is much greater in the vertical direction and flatter horizontally. This causes a visual distortion that requires eyeglasses or contact lenses that also have different powers vertically and horizontally.