Non-24-hour sleep-wake disorder (Non-24) is a condition experienced primarily by totally blind individuals that results in abnormal night sleep patterns and chronic daytime sleepiness. This is a research protocol to develop a patient registry of subjects who may suffer from Non-24 and who are blind. Subjects participate in the study through a phone survey. This registry will be used to better understand, sleep related problems in blind individuals, including the investigation of a potential treatment, recruitment for future clinical studies, and to provide a forum for raising awareness about Non-24. The survey consists of questions regarding the degree of vision impairment and sleep problems that the subjects may be experiencing.