I am sorry to hear that your grandson has juvenile x-linked retinoschisis. Unfortunately there is no possible laser or other treatment to prevent detachment of retina. This is why it is important to regularly see an ophthalmologist so that if a detachment occurs it can be crrected by surgery as early cases carry a better prognosis. To read more on this you can follow this link -
http://www.kellogg.umich.edu/patientcare/conditions/retinoschisis.html. Thanks and best wishes.
Gene therapy may offer a therapeutic option in future as it is showing good results on animal models. Laser was performed to flatten peripheral schis cavities and also decrease the risk of detachment but in many cases it caused retinal detachment itself. I hope, that helps.Thanks.