SARS-CoV-2 particles found in deep retinal layers in patients with COVID-19

Using microscopy, investigators in Brazil analyzed enucleated eyes of patients who had died of the SARS-CoV-2 virus to determine whether viral particles and associated proteins had penetrated into the retinas.

Study design

Fluorescence microcopy of retinal tissue from three retinas were immunostained for S1 and nucleocapsid proteins, and transmission electron microscopy of thin sections was performed. Infection with SARS-CoV-2 was confirmed with nasal swab PCR. All patients had severe pulmonary involvement of COVID-19 requiring intensive care unit management and mechanical ventilation, and eyes were enucleated within 2 hours of death.

Outcomes

The patients ranged in age from 69 to 78 years; two were male. The SARS-CoV-2 spike protein and the nucleocapsid protein were seen in various areas of the retina, including the ganglion cell layer, inner and outer plexiform layers, and inner and outer nuclear layers, as well as the pigment epithelium and choroid. Findings from both electron microscopy and confocal laser scanning microscopy demonstrated that double-membrane vacuoles were located in the perinuclear region of the cells.

Limitations

The study involved a small sample size due to challenges in obtaining the eyes. Complete ophthalmologic exams were not performed on all patients. Additionally, the images obtained in this study did not show the virus structure with the same quality of those obtained in cell cultures.

Clinical significance

The study demonstrated that presumed SARS-CoV-2 viral particles may reach the many layers of the human retina. The results may help clarify the pathophysiologic mechanisms of SARS-CoV-2 and improve our understanding of the sequelae of COVID-19. The study results may also direct avenues of future research to determine whether the ocular manifestations of COVID-19 are due to direct viral invasion or occur as a result of the microvascular and immunologic changes of the virus.