Kim J, et al. - In this first nationwide population-based epidemiologic study, researchers investigated how the development of retinal vein occlusion (RVO) is associated with blood high-density lipoprotein cholesterol (HDL-C). Between January 2009 and December 2012, 23,149,403 people aged 20 years or older who underwent the Korean National Health Screening Program examination were included. The RVO group comprised 117,639 patients with an initial diagnosis of RVO made between 2009 and 2015. Outcomes of this retrospective, nationwide, population-based cohort study suggest that low HDL-C have a significant correlation with RVO development. Patients with a younger age, male sex, current smoking habit, diabetes mellitus (DM), and hypercholesterolemia showed a higher association between the development of RVO and HDL-C. Furthermore, they noted a significant synergistic effect of low HDL-C level with obesity and hypertension.