Orthokeratology lenses are custom-made lenses which the child has to use overnight. When the child wakes up they can see clearly and be free of glasses throughout the day. These lenses mold the shape of the front surface of the cornea gently and precisely, making the optical signals fall directly onto the retina. Orthokeratology (Ortho-k) lenses treat myopia by flattening the cornea in the center. Previous studies have shown 40-60% reduction in the rate of myopia progression in Ortho-K compared to common eye glasses.