© 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Purpose: This study aimed to evaluate posterior ocular structural and vascular changes in severe coronavirus disease 2019 (COVID-19) patients. Methods: This was an observational, prospective, and controlled study including 106 eyes of 53 severe COVID-19 patients, compared to after recovery and 106 eyes of 53 age- and gender-matched healthy controls. All subjects were previously healthy adults and were assessed using spectral domain optical coherence tomography (SD-OCT) and ImageJ software. Subfoveal over a 1500-μm span and macular over a 6000-μm span cross-sectional areas of the vascular, stromal, and total choroid were measured. Results: Of the 53 included patients, 28 (52.8%) were male, and 25 (47.2%) were female, with a mean age of 50.2 ± 7.4 years. In the active period of the disease, compared to after recovery and healthy controls, the outer plexiform layer thickness showed a significant increase (p = 0.004), and mean choroidal thickness was significantly higher (p < 0.0001); however, choroidal vascularity was significantly lower (p < 0.0001). The stromal area to vascular area (S/V) ratio of the choroid was significantly increased (p < 0.0001). All quadrants of the peripapillary retinal nerve fiber layer (RNFL) thicknesses were significantly increased (for all, p < 0.05). The reflectivity of OCT echo of the choroid and peripapillary RNFL was significantly higher (p = 0.023, p < 0.0001, respectively). Conclusion: This study detected significant posterior ocular structural and vascular alterations in patients with severe COVID-19 infections. These findings may be associated with direct host-virus interaction or linked to an autoimmune process, vasculopathy, or viral-mediated inflammation.