Previous research has shown that COVID-19 can impact ocular health.
Research has shown that COVID-19 can have ocular manifestations and that retinal changes may occur as a result of secondary microvascular and immunological changes. Even more, real-time polymerase chain reaction and immunological methods have suggested that S and N proteins may be present in the eyes of infected patients.
To further evaluate the presumed presence of the virus particles and related proteins in the eyes, a team of Brazilian investigators, led by Carlla Araujo-Silva, MSc, examined fluorescence microcopy of tissues immunostained for S1 and nucleocapsid proteins as well as transmission electron microscopy of thin sections among deceased patients.
Araujo-Silva’s team processed the retinas from the 3 patients at a hospital in São Paulo, Brazil from June 23 – July 2, 2020. Of the 3 individuals, 2 were men, and the age at death ranged from 69 – 78 years.
All patients had been admitted to the intensive care unit, received mechanical ventillation, and experienced severe pulmonary involvement from COVID-19, with >50% of their lungs showing multifocal pulmonary ground-glass opacities according to chest tomography imaging.
They were receiving heparin, antibiotics, and corticosteroids prior to death.
Their eyes were enucleated within 2 hours post-death, and “the anterior and posterior segments were separated at the ora serata and then fixed in a freshly prepared solution in a 0.1 M cacodylate buffer; pH 7.2 of glutaraldehyde, 2.5%; and formal- dehyde, 4%, for at least 30 days before further processing.”
The team then analyzed ultrastructure analysis of various retinal and choroid sections from the patients.
“The presence of particles between with a diameter varying from 60 to 70 nm was seen in the perinuclear region of cells of the inner nuclear layer (INL), especially in double- membrane reticular structures recently characterized as derived from the changes in the endoplasmic reticulum in- duced by SARS-CoV-2,” the investigators wrote.
These particles were also observed in capillary endothelial cells within the INL. Images showed surface projections that looked similar to those observed in isolated and well-preserved virus particles. Electrodense granularity was seen in the particle.
Virus particles were also found in the perinuclear and cytoplasmic region within the outer nuclear layer.
Overall, they were able to visualize S and N viral proteins and identify virus particles with morphology similar to particles observed in COVID-19-infected cell cultures.
“Given that these findings support the presence of viruses that presumably are SARS-CoV-2 in the retina, research should assess whether retinal changes are related only to secondary microvascular and immunological changes, coincidence to a very prevalent infection or the virus’ direct presence, or a combination of these,” Araujo-Silva and colleagues wrote.
They further indicated that their findings could help shed light on the virus’ pathophysiological mechanisms, which, in turn, may provide additional direction for future research.
The study, “Presumed SARS-CoV-2 Viral Particles in the Human Retina of Patients With COVID-19,” was published online in JAMA Ophthalmology.