Because of the heterogeneity of ROP well designed and specific clinical trials must show effectiveness of such therapy. So far there are no such trials with so called "stem cells". Retinal vessel damage needs to be corrected (laser, cryotherapy, anti VEGF antibodies, etc) before these stem cells (if they are really stem cells) are able to repair a tissue such as the retina.
I would be extremely careful in going to such clinics offering treatment without regulatory approval. You do not know what will be injected, but you are likely to pay a substantial amount for this "treatment". You may wish to discuss this topic with experts at http://focusrop.com/rop