Background/Objectives <p>Emerging research suggests obstructive sleep apnoea (OSA) as a potential risk factor for retinal vein occlusion (RVO), but the impact of sex, race, and ethnicity, and the role of OSA in RVO progression, remains unclear. This study explored demographic differences in the association between OSA and RVO and compared the severity of RVO in patients with and without OSA.</p> Subjects/Methods <p>This retrospective cohort study analysed aggregated, de-identified electronic health record data of US patients. Adults who received ophthalmological services were grouped by baseline RVO status (RVO-naïve and preexisting RVO). The RVO-naïve group was further stratified by sex, race, and ethnicity. Patients with and without OSA were compared within each group to evaluate the risk ratio for primary outcomes: new RVO diagnoses in RVO-naïve individuals and RVO complications or invasive treatments in those with preexisting RVO.</p> Results <p>Among RVO-naïve adults, OSA was associated with an increased risk of RVO in females (<i>n</i> = 148,036, RR = 1.28, CI = 1.14–1.45), males (<i>n</i> = 134,348, RR = 1.35, CI = 1.19–1.52), non-Hispanic White (<i>n</i> = 146,124, RR = 1.32, CI = 1.17–1.49), Hispanic/Latino (<i>n</i> = 30,898, RR = 1.77, CI = 1.30–2.40) patients. A marginally increased risk was seen in Black patients (<i>n</i> = 57,798, RR = 1.26, CI = 1.05–1.50), but not in Asian patients (<i>n</i> = 6860, RR = 1.21, CI = 0.71–2.07). Among 5264 adults with preexisting RVO, those with OSA had higher rates of macular oedema (RR = 3.70, CI = 3.17–4.31), vitreous haemorrhage (RR = 2.29, CI = 1.64–3.20), neovascularization (RR = 2.22, CI = 1.69–2.91), and photocoagulation (RR = 1.73, CI = 1.29–2.33), but not vitrectomy (RR = 1.13, CI = 0.74–1.72).</p> Conclusions <p>OSA is associated with an increased risk of RVO among various populations, especially among Hispanic/Latino. Among patients with preexisting RVO, OSA is associated with indicators of more severe RVO.</p>