Glial cell–derived neurotrophic factor, ciliary neurotrophic factor (CNTF), brain-derived neurotrophic factor (BDNF), basic fibroblast growth factor, and pigment epithelium–derived factor (PEDF) were shown to have beneficial effects in preventing photoreceptor death in several mouse models of retinal degeneration (Unsicker, 2013; Paulus and Campbell, 2016; Pardue and Allen, 2018). Here, BDNF is linked to retinal degeneration.