We chose to treat our animals at P5 both because it represents a physiologically appropriate intervention time and because previous rds gene therapy trials have reported difficulties correcting the ERG defect in adult rds mice, whereas correction was observed following neonatal gene transfer [30], [31]. The high rates of transfectivity we report here after P5 injection of rds +/− mice combined with the high rates of transfectivity we previously reported after subretinal injection in adult WT mice [13] show that these DNA-nanoparticles can effectively transfect both mitotic and post-mitotic (terminally differentiated) retinal cells. Furthermore, our ability to drive long-term expression (up to four months) suggests that CK30PEG-compacted DNA-nanoparticles may not be subject to some of the practical impediments that have limited the utility of other forms of non-viral gene therapy. We have shown partial structural and functional rescue of the rds +/− phenotype by delivery of compacted DNA-nanoparticles containing WT Rds. These nanoparticles offer a promising gene therapy modality that, with further development, may find practical applications in the treatment of a wide variety of hereditary ocular diseases.