Orthokeratology (Ortho-K/OK lens) is the fitting of special customized gas permeable contact lenses that you wear overnight. While you are asleep, the lenses gently reshape the front surface of your eye (cornea) so you can see clearly the following day after you remove the lenses when you wake up.

This method can be used as an alternative to eyeglasses, refractive surgery, or for those who prefer not to wear contact lenses during the day.

More commonly, OK contact lenses are widely used for myopia control in children who have progressive myopia. Many studies have also shown the effectiveness of these lenses in controlling and stabilizing myopia in children. 

It also allows the children who do not tolerate glasses well or have an active lifestyle, to be glasses free throughout the day, and have myopia control present at the same time.