An Open Label Clinical Trial of Retinal Gene Therapy for Choroideremia

Inclusion Criteria: * The research subject is willing and able to give informed consent for participation in the study. * Male aged 18 years or above. * Diagnosed with choroideremia (with genotyping or evidence of lack of the gene product with immunohistochemistry) and in good health. * Active degeneration of the retina (the expectation of significant decline in visual function without any intervention over the subsequent 5 years) with OCT (optical coherent tomography) changes visible within the macula. * Willingness to allow his general physician and ophthalmologist, if appropriate, to be notified of participation in the study. Exclusion Criteria: The participant may not enter the study if ANY of the following apply. * Female or child research subject (under the age of 18). * Men unwilling to use barrier contraception methods, if relevant. * Previous history of retinal surgery or ocular inflammatory disease (uveitis). * Grossly asymmetrical retinal disease or other ocular morbidity which might confound adopting the fellow eye as a long-term comparator. * Any other significant systemic disease or disorder which, in the opinion of the investigator, may either put the research subject at risk because of participation in the study, or may influence the result of the study, or the research subject's ability to participate in the study. This would include a contraindication to oral prednisolone, such as a history of gastric ulcer). * Research subjects who have participated in another research study involving an investigational product within the past year.