You just need to use it during the night and shape your eye in the way it is needed, and you will be able to see normally the whole next day without glasses. It saves you the trouble of wearing glasses or contacts during the daytime. But they are more expensive, usually the half price of lasik surgery.
If you have lower prescription, you will get your good vision very soon if you have OrthoK treatment.People will get significant vision improvement within two hours. They will achieve good vision within the first week. If you have higher prescription, it will take you two to four weeks to achieve good vision.