This is a prospective, observational study designed to evaluate the long-term safety and efficacy of RGX-314. Eligible participants are those who were previously enrolled in a clinical study in which they received a single subretinal administration of RGX-314 in their study eye. Enrollment of each participant in the current study should occur after the participant has completed either the end of study or early termination visit in the previous (parent) clinical study. Participants will be followed for up to 5 years post-RGX-314 administration (inclusive of the parent study). After enrollment and a 6-month follow-up visit, participants will attend at least annual study visits through the end of the 5-year post-RGX-314 administration follow-up period. Additionally, an interventional fellow eye treatment substudy will evaluate the safety, efficacy, and immunogenicity of subretinal RGX-314 administration in the fellow eye of participants having bilateral disease who previously received a subretinal injection of RGX-314 in their study eye. Participants who qualify for the substudy will receive subretinal administration of RGX-314 in their fellow eye and complete 13 study visits in a 54-week period. Following completion of the substudy participants will continue in the observational portion of the study for up to 5 years post RGX-314 administration in their fellow eye.