Background: - X-linked juvenile retinoschisis (XLRS) is caused by changes in the RS1 gene. These changes cause abnormal function of the eye protein retinoschisin. Without normal retinoschisin, the layers of the retina split and vision is lost. Researchers want to try to introduce a healthy RS1 gene into eye cells, to see if this helps retinal cells make healthy retinoschisin. They will put the gene in a virus. The gene and virus package is known as a gene transfer vector (AAV-RS1 vector). Objectives: - To see if the AAV-RS1 vector is safe to use in people. Eligibility: - Adults 18 and older with a mutation of the RS1 gene, 20/63 vision or worse in one eye, and XLRS. Design: * Participants will be screened with genetic tests to confirm XLRS. They will have a medical history and physical and eye exams. * At visits 1-2, participants will have some or all of the following: * Medical history * Physical exam * Blood and urine tests * Tuberculosis skin test * Eye exam * Vision tests (for one test an intravenous line will be placed in the arm. A dye will be injected that will travel to the blood vessels in the eye). * At visit 3, the AAV-RS1 vector will be injected with a needle in the study eye. Participants pupils will be dilated. They will get numbing eye drops. * Visits 4-13 will occur in the 18 months after gene transfer. Many of the above tests will be repeated. Participants will discuss any side effects. * Visits 14-17 will occur yearly between years 2 and 5. * After year 5, participants will be contacted yearly by phone for up to 15 years.