Liu and Ying et al. had suggested that 35 retinitis pigmentosa patients were treated with repeat intravitreal injections of NGF (30 μg/0.15 mL) (final concentration was about 6 μg/mL in the vitreous cavity) to protect the RPE after safety evaluation in rats and rabbits [33] and no toxic reactions or side-effects were evident. This evidence concerns the gene NGF and retinitis pigmentosa.