Orthokeratology, or Ortho-K, or simply OK, is using rigid contact lenses to reshape your corneas. This enables you to wear the lenses for a period of time, take them out, and be able to see without contact lenses or glasses at all, for a period of time. ANSWERS Modern Orthokeratology is the use of specially fitted hard gas permeable extended wear contact lenses that within a few days of full time wear can remove moderate amounts of nearsightedness for short periods of time. To maintain the change the lenses are worn as retainers while sleeping and taken off during the day until the changes become more permanent. Then the lenses are worn as needed any time to remove any blur that's returning.