CR2 and glaucoma: Despite the potential therapeutic evidence for BDNF, EPO, NRF2, C3, Scng guided CRISPR/Cas9, PEDF + hMSC, CR2-Crry, STC-1, NGB, sFasL, and miR-21, many shared limitations in all the studies included a limited model of glaucoma or related ocular disease, pre-emptive intravitreal injection of the gene therapy, and a lack of regulation of gene therapy expression.