Inclusion Criteria:  Have RPGR-associated retinal dystrophy Are able to give informed consent or assent, with the guidance of their parent/guardian where appropriate Are able to undertake age-appropriate clinical assessments as specified in the protocol  Exclusion Criteria:  Are unable or unwilling to undertake consent or clinical testing Participated in another research study and had intraocular surgery within 3 months of screening Significant ophthalmologic diseases