PURPOSE: Retinal vascular occlusion is a leading cause of profound irreversible visual loss, but the understanding of the disease is insufficient. We systematically investigated the age, gender, and laterality at the onset of retinal artery occlusion (RAO) and retinal vein occlusion (RVO) in the IRIS® Registry (Intelligent Research in Sight). DESIGN: A retrospective registry cohort. PARTICIPANTS: Retinal vascular occlusion cases participating in the IRIS Registry. METHODS: All cases diagnosed as retinal vascular occlusion in the IRIS Registry between 2013 and 2017 were included. Cases with unspecified gender or laterality were excluded when conducting the relevant analyses. Cases were categorized based on diagnosis codes into RAO, with subtypes transient retinal artery occlusion (TRAO), partial retinal artery occlusion (PRAO), branch retinal artery occlusion (BRAO), and central retinal artery occlusion (CRAO), and into RVO, with subtypes venous engorgement (VE), branch retinal vein occlusion (BRVO), and central retinal vein occlusion (CRVO). Age was evaluated as a categorical variable (5-year increments). We investigated the association of age, gender, and laterality with the onset frequency of retinal vascular occlusion subtypes. MAIN OUTCOME MEASURES: The frequency of onset of RAO and RVO subtypes by age, gender and laterality. RESULTS: A total of 1,251,476 retinal vascular occlusion cases were included, 23.8% of which were RAO, while 76.2% were RVO. 1,248,656 and 798,089 cases were selected for analysis relevant to gender and laterality, respectively. The onset frequency of all subtypes increased with age. PRAO, BRAO, CRAO, and CRVO presented more frequently in men (53.5%, 51.3%, 52.6%, 50.4%), while TRAO, VE, and BRVO presented more frequently in women (54.9%, 56.0%, 54.5%). BRVO and all RAO subtypes showed a right-eye onset preference (BRVO 51.0%, TRAO 51.7%, PRAO 54.4%, BRAO 53.5%, CRAO 53.4%), while VE and CRVO exhibited a left-eye onset preference (VE 53.3%, CRVO 50.9%). CONCLUSIONS: While retinal vascular occlusion incidence increases with age regardless of subtypes, we found various subtype-specific disease onset differences related to gender and, in particular, ocular laterality. These findings may improve understanding of the specific etiology of retinal vascular occlusions of different subtypes and their relationship with structural and anatomic asymmetries of the vascular system.