The study has been terminated due to limited participant enrollment.

Primary objective: To examine the short-term effects of of simvastatin on the vision on males with choroideremia, evaluated by full-field scotopic threshold testing. The investigators hypothesize that they will see a reversible decrease in the dark-adapted vision in participants taking simvastatin.

Inclusion Criteria:

• Participant is willing and able to give informed consent for participation in the study
• Male
• Diagnosed with choroideremia and in good health
• Willing to allow his general practitioner and consultant, if appropriate, to be notified of participation in the study
• Over age of 18 years

Exclusion Criteria:

• Female
• Significant health disease, disorder, or medication, which, in the opinion of the investigator, would put the patient at risk if he were to take simvastatin
• Already taking simvastatin or another statin