ObjectiveProgressive retinal atrophy has been described after subretinal gene therapy utilizing the adeno-associated virus (AAV) vector platform. To elucidate whether thIS atrophy is a consequence of inherent properties of AAV, or if it is related to the surgical trauma of subretinal delivery, we analyzed data from an IND-enabling study for PDE6A gene therapy in non-human primates. DesignAnimal study (non-human primates), retrospective data analysis SubjectsForty eyes of thirty healthy non-human primates (macaca fascicularis) were included in the analysis. Two AAV dose levels (low: 1x10E11, high: 1x10E12) were compared to sham-injection (balanced saline solution; BSS). Twenty untreated eyes were not analysed. MethodsAnimals were treated with a sutureless 23G vitrectomy and single subretinal injections of AAV.PDE6A and/or BSS. The follow up period was 12 weeks. Atrophy development was followed using fundus-autofluorescence (AF), optical coherence tomography (OCT), fluorescence angiography (FA) and indocyanine green angiography (ICGA). Main Outcome MeasuresArea [mm2] of retinal pigment epithelium (RPE) atrophy on AF. Presence of outer retinal atrophy on OCT. Area [mm2] of hyperfluorescence in FA and hypofluorescence in ICGA. ResultsProgressive atrophy at the injection site developed in 54% of high dose, 27% of low dose, and 0% of sham-treated eyes. At the end of observation, the mean±SD area of atrophy in AF was 1.19±1.75 mm2, 0.25±0.50 mm2 and 0.0±0.0 mm2 respectively (sham x high dose: p=0.01). Atrophic lesions in AF (p=0.01) and FA (p=0.02) were significantly larger in high dose eyes, compared to sham-treated eyes. Rate of progression in high dose eyes was 4.1x higher compared to low dose eyes. ConclusionSubretinal injection of AAV.PDE6A induced dose-dependent, progressive retinal atrophy at the site of injection. Findings from multimodal imaging were in line with focal, transient inflammation within the retina and choroid and secondary atrophy. Atrophic changes after gene therapy with AAV-based vector systems are not primarily due to surgical trauma and increase with the dose given.