A return to the original refractive state. This regression phenomenon occurs with both myopic [myopia] and hyperopic [hyperopia] corrections. It occurs more commonly with smaller ablation diameters and with abrupt transition zones at the edge of the laser treatment areas. Some surgeons have suggested that the epithelium overgrows as if nature abhors a vacuum and overreacts to fill in the space. Steroid medications can usually be used to regulate and control regression.