Personal light exposure is a modifiable component of the health exposome, but its everyday determinants remain poorly understood. We conducted an observational, harmonised, multi-country wearable study of ocular light exposure in 191 adults across nine sites in Sweden, the Netherlands, Germany, Spain, Turkey, Costa Rica, and Ghana, comprising 1,480 participant-days. Participants wore calibrated light loggers near the corneal plane and at chest level and completed repeated contextual assessments. Average daytime exposure remained below recommended melanopic levels, with adherence varying by site, daily phase and photoperiod. Exposure generally increased with latitude despite greater year-round sunlight at lower latitudes, consistent with behavioural filtering through shade-seeking, indoor living or heat avoidance. Individual and activity-level differences explained more variation than site. Daylight access, outdoor activity and micro-environment were the strongest correlates. These findings support personalized, context-sensitive light interventions and establish ocular light exposure as a measurable exposomic factor relevant to health.