Purpose <p>This study assessed posterior segment microvascular changes in patients with cytomegalovirus (CMV) anterior uveitis (AU) during acute episodes by comparing retinal and choroidal changes to those in patients with HLA-B27 AU and healthy controls, aiming to evaluate their impact on visual outcomes.</p> Methods <p>In this retrospective study, 85 patients with CMV AU, 93 with HLA-B27 AU, and 80 healthy controls underwent comprehensive ocular evaluations, including optical coherence tomography (SS-OCT) and OCT angiography (OCTA). Retinal thickness, vascular density (VD), and choroidal parameters were evaluated, and statistical comparisons were made among groups.</p> Results <p>Posterior microvascular changes were observed in both uveitis groups. In CMV AU, parafoveal superficial vascular plexus (SVP) VD, deep capillary plexus (DCP) VD, and choriocapillaris flow deficit (CCFD) areas were significantly associated with visual acuity. CMV AU patients showed lower parafoveal SVP and DCP VD and larger CCFD areas than healthy controls. Compared to HLA-B27 AU, CMV AU exhibited a lower DCP VD and higher CCFD area, indicating distinct retinal and choroidal changes.</p> Conclusion <p>Posterior microvascular changes occur in acute AU, affecting visual acuity, even without evident retinal or vitreous involvement. The effects of CMV AU on the retinal and choroidal microvasculature highlight the need for posterior segment evaluation to manage AU.</p>