GDNF and central nervous system disorder: Once more, basic research on retinal dystrophies have paved the way with the identification of several neurotrophic factors, for example, ciliary neurotrophic factor, glial-cell derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF), which seem to arrest the pathological process irrespective of the genetic subtype.70–72 Neurotrophic factors can diffuse away from the cell from which they are secreted and this important property can be used to extend their therapeutic range, especially for central nervous system disorders.