Participants will receive a dose of AAV5 hRKp.RPGR under the retina (low-dose or intermediate-dose) on Day 1 depending on the dosage administered in study MGT009 (NCT03252847) in the past. After receiving the treatment, participants will be assessed for safety.

Participants will receive the treatment dose of AAV5 hRKp.RPGR under the retina (low-dose or intermediate-dose) on Day 1 in the second eye once the safety will be determined in Cohort 1.

The participants who are not willing to undergo surgery or are not eligible for surgery will be assessed in this cohort. They will be assessed yearly until 5 years after their initial eye surgery in previous study MGT009.

AAV5-hRKp.RPGR will be administered sub-retinally.

An AE is any untoward medical occurrence in a clinical study participant administered a pharmaceutical (investigational or non investigational) product. An AE does not necessarily have a causal relationship with the intervention. An AE can be any unfavorable and unintended sign (including an abnormal finding), symptom, or disease temporally associated with the use of a medicinal (investigational or non investigational) product, whether or not related to that medicinal (investigational or non investigational) product.

Change from baseline in BCVA by ETDRS chart letter scores in monocular assessment of the second treated eye will be assessed. BCVA was measured using the ETDRS Scale (ranging from 0 to 100 letters) in the study eye. An increase in the number of letters read correctly means that vision has improved and vice-versa.

Change in LLVA by ETDRS chart letter scores from baseline in monocular assessment of second treated eye will be assessed. Visual function assessments included LLVA assessment in each eye by ETDRS letters. The letter score ranges from 0 (worse score) to 100 (best score), and a gain in LLVA from baseline indicates an improvement in visual acuity.