A simplified screening test for the identification of individuals with diminished vision in developing countries

The mammalian visual system, particularly retinal ganglion cells, has been used for studying the functions of neurotrophic factors on neurons for many years. The major biological effects of neurotrophic factors on retinal ganglion cells observed so far are the promotion of viability and axonal regeneration. However, there are still some controversies regarding the effects of neurotrophic factors on retinal ganglion cells in the literature. This review is aimed to summarize the available information on the biological actions of these neurotrophic factors on survival and axonal regeneration of retinal ganglion cells and the expressions of neurotrophic factor receptors in the retina. Generally, brain-derived neurotrophic factor, neurotrophin-4/5, fibroblast growth factor and glial cell line-derived neurotrophic factor increase the survival of retinal ganglion cells while the effect of ciliary neurotrophic factor on the viability of adult retinal ganglion cells is controversial. The ciliary neurotrophic factor is the only effective factor in promoting long distance axonal regeneration of retinal ganglion cells whereas brain-derived neurotrophic factor and neurotrophin-4/5 only enhance neurite sprouting within the retina.