As the eyeball grows, the retina moves further back in relation to the cornea and lens. Hence it is likely that a minus number may increase with time. There is no medically accepted method by which this can be prevented, including use of contact lens. In fact this is like making your child wear a hard hat over his head to prevent the height from increasing! However, it is a fact that numbers, like height are genetically predetermined and so a child’s minus number could stop increasing suddenly at say age 12 or 14. If at that time, the child was doing natural exercises or wearing a contact lens or putting honey in the eyes or even practicing urine therapy, that particular treatment is given wide publicity by gullible parents. This results in neighbours, friends and relatives insisting that this or that therapy is incredibly successful in preventing increase in numbers!
There is growing evidence that children who spend more time outdoors in physical activity have less increase in minus number.