Aim: To assess retinal structure and function over a 3-year period in a group of five RPE65-/- dogs treated by unilateral rAAV-mediated subretinal gene transfer. Methods: Post-operative functional follow-ups were performed using simultaneous, bilateral, full-field ERGs. Structure was evaluated by SLO using FL and ICG angiography and by EM. Results: Significant improvement of retinal function was observed through ERGs approximately 4 weeks following surgery. Scotopic b-wave amplitudes peaked 3 months after surgery. Then there was a successive reduction, although greater amplitudes than base-line values were observed at all post-operative time points. A-wave amplitudes increased at a later time than b-wave amplitudes and were sustained throughout the follow-up period. The increased cone function was preserved longer than the rod function. Angiography showed structural changes at the site of injection, corroborated by photoreceptor destruction observed ultrastructurally. Immediately adjacent to the subretinal injection area photoreceptor outer segments appeared normal. Conclusion: Despite local structural alterations at the subretinal injection site, subretinal gene transfer in the RPE65 null mutation dog effectively increases retinal function for at least 3 years after surgery.