Disclosed are, among other methods, methods for reactivating retinal ganglion cells in mammals by administering an effective amount of channelrhodopsins (such as ChrimsonR), or an effective amount of such channelrhodopsins (such as ChrimsonR) fused to a fluorescent protein, in the form of protein or nucleic acids, and compositions thereof. The methods may include a light stimuli level inducing RGCs response that is below radiation safety limit. The methods may include delivery by an adenoassociated virus vector. The methods may include use of a CAG promoter. The methods may result in a long term expression of an effective amount of the channelrhodopsins (such as ChrimsonR protein).