How safe is ortho k treatment for nearsighted eyes?

Mostly: Ortho k is a systemic of molding mildly myopic eyes to correct the vision by wearing a series of too flat hard lenses which push the center of the eye inwards. It is a tradeoff since to maintain any improvement, you have to wear a "keeper" lens at night. It was developed as a way to keep non-professionals like optometrists in the vision correction game. It reverses when you stop the lenses.