Laser Eye Surgery has improved tremendously from the mid-1990s. New generation lasers have improved both the percentage of patients with 20/20 vision after surgery and the quality of vision. The reason behind this has to do with the shape of the cornea (the cornea is the clear front part of the eye which is reshaped by the laser treatment.)
In nature, there are 2 types of cornea shapes, prolate and oblate. Animals with great vision such as eagles and hawks have prolate corneas. Animals with not-so-great vision like frogs have oblate corneas. The human cornea is naturally prolate in shape like that of a hawk, so by nature we have great visual potential.