Not long after RK, or radial keratotomy, came a new technique for shortening the focal length of the nearsighted eyeball. This was the long awaited PRK, photorefractive keratotomy. The procedure reshapes the cornea, in effect, shortens the focal length. A laser with low-heat UV radiation removes corneal material literally microscopic layers at a time. The procedure is robotic; the laser is pre-programmed, literally vaporizing a few molecules with each pulse from just the right place on the corneal surface.