The MOONLENS Orthokeratology (Ortho K) Contact Lens System for Overnight. This is a unique contact lens product with a progressive lens design and fitting system that helps manage and temporarily correct myopia, as well as mild astigmatism. The Ortho K MOONLENS is meant to be worn overnight. It works by altering the curvature of the cornea while the patient sleeps, which thereby reduces the excessive focusing power of the myopic eye.