Ortho-k can have both a corrective and preventive/control effect in childhood myopia. However, there are substantial variations in changes in eye length among children and there is no way to predict the effect for individual subjects.
See:
The longitudinal orthokeratology research in children (LORIC) in Hong Kong: a pilot study on refractive changes and myopic control.
Cho P, Cheung SW, Edwards M.
Curr Eye Res. 2005 Jan;30(1):71-80.
