COVID Eye Infection
updated January 29, 2024
The most recent variants exhibit a heightened ability to infect individuals, demonstrating a stronger affinity for ACE-2 receptors. These receptors are present not only in our nasal passages, throat, tonsils, and lungs but also throughout the entire body, including the eyes and ears.
While COVID-19's transmission through the eyes has been a relatively rare occurrence, the latest variants raise concerns about an increased likelihood of infection through ocular exposure. This can happen either through aerosolized droplets or by touching surfaces with viral particles and subsequently rubbing one's eyes.
Symptoms such as dry eyes, a sensation of foreign particles, blurred vision, or manifestations similar to pink eye may indicate a potential COVID-19 infection. Recognizing these signs becomes crucial in identifying and responding to the evolving dynamics of virus transmission.
Figure 1: “Proposed mechanisms of ocular COVID-19 transmission. The conjunctiva may serve as a direct inoculation site of infected droplets. Given a sufficiently high viral load, some virus may be able to evade the antimicrobial agents of the tear film and directly gain access to conjunctival and corneal cells before eventually entering general circulation. TMPRSS2 proteins found on the surface of ocular cells activate the virus spike protein through proteolytic cleavage. Once activated, the spike protein can bind to ACE2 receptor and enter a host cell.”(2)
"After incorporating the surface area of the eyelids and brows, roughly 4000 mm2 and 3000 mm2 respectively, the total ocular surface area surpasses 10,000 mm2. This is two orders of magnitude greater than the nares and mouth."(3)
Insights from Google Trends
Google searches for terms like "Pink eye" and "Conjunctivitis" have seen a significant surge since the mitigation protections were eased and eventually halted. While factors such as weakened immune systems might contribute to this increase, it is likely that a significant portion is attributed to COVID-19 infections.
Despite the fact that many individuals might not readily link these eye conditions with COVID-19, being mindful of these trends enables us to make that connection and aid in making better decisions regarding treatments. For example, antibiotic eye drops commonly prescribed to treat pinkeye won’t help and could aggravate the situation. By sharing this information with doctors, friends and family, we can contribute to raising awareness, helping others identify signs, and enhancing the protection of ourselves and our loved ones.
An early study in 2020, "found that the average duration of conjunctival congestion was 5.9 ± 4.5 days (mean [SD]), ranging from two to twenty-four days" (1)
Symptoms:
Dry eye
Blurred vision
Foreign body sensation
Ocular Pain
Conjunctivitis
“Outside of the passive defense elements in the cornea and conjunctiva, early responding non-specific immune cells are some of the most important defenses our eye use to control and fight infections. "Neutrophils reside in corneal endothelium after migrating through the limbal vasculature by diapedesis. The neutrophil-derived interferon-α (IFN-α) plays an important role in viral immunity" (4)
Neutrophils, residing in the corneal endothelium, produce interferon-α (IFN-α), a key player in viral immunity. However, a challenge arises as COVID has evolved to infect neutrophils, impacting peripheral blood lymphocyte counts and diminishing various immune cell populations, including CD19+ B cells, CD8+ T cells, and CD4+ T cells.
"Infected neutrophils had a direct effect on peripheral blood lymphocyte counts, with decreasing numbers of CD19+ B cells, CD8+ T cells, and CD4+ T cells."(5)
Another layer of defense comes from macrophages, strategically positioned in both the conjunctiva and corneal stroma, playing a crucial role in the initial defense by connecting the innate and adaptive immune systems.
"Macrophages are thought to be located in both conjunctiva and corneal stroma. Macrophages play an important role in initial defense connecting the innate and adaptive immune systems." (4)
Despite these defenses, COVID can still interfere with the immune response by infecting macrophages.
"SARS-CoV-2 infection drives an inflammatory response in human adipose tissue through infection of adipocytes and macrophages" (6)
This capability to infect various cells in the immune system and throughout the body raises concerns, especially with the enhanced binding to ACE-2 receptors, potentially leading to increased eye infections.
A study from 2021, found the presence of SARS-Cov-2 in tears and conjunctiva of patients with COVID. They conclude the ocular transmission is possible and preventative measures should be taken. (7)
Children, in particular, may be more susceptible to eye infection of COVID due to their proximity to others and their tendency to touch surfaces and then rub their eyes.
Maintaining excellent hand hygiene remains crucial, but the use of properly worn, high-quality N-95/KN-95 masks is equally important. These masks can help limit the spread of potentially infected aerosolized droplets, reducing exposure to high viral loads.
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References with additional quotes.
( Some references have additional X/Tweet size quotes for sharing)
1.(2020) "Ocular manifestations and clinical characteristics of 535 cases of COVID-19 in Wuhan, China: a cross-sectional study"
Conclusions: "Conjunctival congestion is one of the COVID related ocular symptoms, which could occur as the initial symptoms. Frequent hand–eye contact may be the risk factor for conjunctival congestion in COVID patients. Screening of patients with conjunctival congestion by ophthalmologists is advocated during the outbreak of COVID. It is essential to provide eye-care equipment and strengthen education on eye protection."
https://onlinelibrary.wiley.com/doi/full/10.1111/aos.14472
2. (2021) "Posterior ocular structural and vascular alterations in severe COVID-19 patients"
"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." https://link.springer.com/article/10.1007/s00417-021-05420-9
3.( 2021) "Ocular transmission and manifestation for coronavirus disease: a systematic review"
"the highest prevalence of ocular conjunctivitis associated with SARS-CoV-2 was 32%. Thus, SARS-CoV-2 can evidently infect the eye, as revealed in the conjunctival secretions of COVID-19 patients."
Conclusion: "The available data reflect the influence of the ocular structure on SARS-CoV-2. The analysis showed that ocular manifestation is an indication for SARS-CoV-2, particularly conjunctivitis." https://academic.oup.com/inthealth/article/14/2/113/6287220
4. (2022) "After incorporating the surface area of the eyelids and brows, roughly 4000 mm2 and 3000 mm2 respectively, the total ocular surface area surpasses 10,000 mm2. This is two orders of magnitude greater than the nares and mouth."
"As this large area frequently contacts respiratory droplets, contaminated fingers and fomites, it is important to consider possible transmission of SARS-CoV-2 through the eye."
"Proposed mechanisms of ocular COVID-19 transmission. The conjunctiva may serve as a direct inoculation site of infected droplets. Given a sufficiently high viral load, some virus may be able to evade the antimicrobial agents of the tear film and directly gain access to conjunctival and corneal cells before eventually entering general circulation. TMPRSS2 proteins found on the surface of ocular cells activate the virus spike protein through proteolytic cleavage. Once activated, the spike protein can bind to ACE2 receptor and enter a host cell. Other hypotheses focus on nasolacrimal transmission of SARS-CoV-2 from the eye to the lungs in humans. Virus may do this by spanning the length of the nasolacrimal duct through repeated reinfection and replication of neighboring cells. Alternatively, the virus may travel in a replication-independent manner via ciliary movement by the cells which line the nasolacrimal duct"
Conclusions: "Based on the existing literature, we assert that the eyes act as an additional entry point for SARS-CoV-2. While current data is controversial on the feasibility of viral RNA isolation from the tear films of COVID-19 patients, SARS-CoV-2 is likely to be found in the ocular secretions of high-viral load patients with active conjunctivitis. The infected ocular fluid serves as a nidus of replication and vector for transmission to conjunctival, corneal, scleral, and nasolacrimal tissue. Like other respiratory diseases, SARS-CoV-2 can persist in the tear film despite antimicrobial peptides and progresses to the respiratory or gastrointestinal tracts through the nasolacrimal duct."
https://link.springer.com/article/10.1007/s11010-021-04336-6
5. SARS-CoV-2 Dysregulates Neutrophil Degranulation and Reduces Lymphocyte Counts
" SARS-CoV-2-infected neutrophils had a direct effect on peripheral blood lymphocyte counts, with decreasing numbers of CD19+ B cells, CD8+ T cells, and CD4+ T cells. Together, this study highlights the independent role of neutrophils in contributing to the aberrant immune responses observed during SARS-CoV-2 infection that may be further dysregulated in the presence of other immune cells
https://www.mdpi.com/2227-9059/10/2/382
Tweet size for above: SARS-CoV-2 Dysregulates Neutrophil Degranulation and Reduces Lymphocyte Counts
"Infected neutrophils had a direct effect on peripheral blood lymphocyte counts, with decreasing numbers of CD19+ B cells, CD8+ T cells, and CD4+ T cells."
https://www.mdpi.com/2227-9059/10/2/382
6. "SARS-CoV-2 infection drives an inflammatory response in human adipose tissue through infection of adipocytes and macrophages"
"We identified two distinct cellular targets of infection: adipocytes and a subset of inflammatory adipose tissue–resident macrophages. Mature adipocytes were permissive to SARS-CoV-2 infection; although macrophages were abortively infected, SARS-CoV-2 initiated inflammatory responses within both the infected macrophages and bystander preadipocytes."
SCIENCE TRANSLATIONAL MEDICINE, 22 Sep 2022, Vol 14, Issue 674, DOI: 10.1126/scitranslmed.abm9151
https://www.science.org/doi/full/10.1126/scitranslmed.abm9151
Rodríguez-Ares T, Lamas-Francis D, Treviño M, Navarro D, Cea M, López-Valladares MJ, Martínez L, Gude F, Touriño R. SARS-CoV-2 in Conjunctiva and Tears and Ocular Symptoms of Patients with COVID-19. Vision (Basel). 2021 Oct 22;5(4):51. doi: 10.3390/vision5040051. PMID: 34698308; PMCID: PMC8544743. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8544743/
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