A Study to Optimize Subretinal Surgical Delivery and to Evaluate Safety and Activity of Opregen in Participants With Geographic Atrophy Secondary to Age-Related Macular Degeneration (GAlette); Adaptive Optics (AO) Retinal Imaging Substudy in Association With Study GR44251

Inclusion Criteria: * Ability to undergo a vitreoretinal surgical procedure under monitored anesthesia care * Diagnosis of GA secondary to AMD * Best corrected visual acuity (BCVA) score ≥ 29 letters and ≤ 60 letters in the study eye as assessed by Early Treatment Diabetic Retinopathy Study (ETDRS) * Pseudophakic (study eye) Exclusion Criteria: * Pregnancy or breastfeeding * History of cognitive impairment or dementia * Any type of systemic disease or its treatment, in the opinion of the investigator, including any medical conditions that could be expected to progress, recur, or change to such an extent that it may bias the assessment of the clinical status of the participant to a significant degree or put the participant at special risk Ocular Exclusion Criteria for Study Eye: * Any current or history of ocular disease other than GA that may confound assessment of the macula * History of retinal detachment * History of vitrectomy, glaucoma-filtering surgery, or corneal transplant * Uncontrolled glaucoma or advanced glaucoma * Any cataract surgery or intraocular surgery within 3 months prior to subretinal surgical delivery of OpRegen * History of other ocular or intraocular conditions that contraindicate the use of an investigational drug or may affect interpretation of the study results or may render the participant at high risk for treatment complications * Any existing posterior segment device or implant Substudy: Inclusion Criteria: \- Participants must meet all of the inclusion criteria described in the parent study GR44251 and have the ability to comply with the substudy protocol Exclusion Criteria: * Participants who meet any exclusion criteria listed in the parent study GR44251 * Past history of seizures, or epileptic seizures due to any cause except for a single febrile seizure in childhood