With millions of cases of COVID-19 worldwide, doctors are learning more and more about this virus, including its impact on the eyes.
Recent studies show that 3% of COVID-19 patients have ocular complications.
However, the true number actually varies between studies when calculated by a meta-analysis of six studies comprising 854 COVID-19 patients.
An article on the topic of Covid-19 and the eyes was published in the Clinical and Experimental Ophthalmology journal in June, 2020.
According to this article, scientists in Turkey examined 93 patients that had been hospitalized with Covid-19. Out of the 93 patients, 20 of these patients (21.5%) presented with at least one of the following ocular symptoms:
- Hyperemia (red eye): 20 patients (21.5%)
- Photophobia (light intolerance): 15 patients (16.1%)
- Itchiness: 13 patients (15.7%)
- Epiphora (watery eyes): 9 patients (9.7%)
- Follicular conjunctivitis (severe conjunctiva swelling): 8 patients (8.6%)
- Burning sensation: 7 patients (8.4%)
- Increased discharge (green or yellow): 6 patients (6.5%)
- Gritty feeling (feels like sand in the eye): 5 patients (6.0%)
- Blurred vision: 4 patients (4.8%)
- Chemosis (swelling of conjunctiva): 3 patients (3.2%)
- Episcleritis (inflammation of eye sclera): 2 patients (2.2%)
The article noted that the primary risk factors for Covid-19 ocular problems included high fever (which served as a biomarker of systemic inflammation) and older age.
Another study cited in the article noted ocular symptoms in 12 (31.6%) out of 38 patients with COVID-19.
A third study conducted in Mexico, found that none of 114 COVID-19 patients that participated in the study had any ocular symptoms.
The retina and optic nerve connection
In the May edition of the Ocular Immunology and Inflammation journal, an article stated that researchers in Germany detected COVID-19 genetic material in the retina of three out of 12 deceased patients. Moreover, prior research has also found the expression of ACE2 (the main receptor SARS-CoV-2 uses to infect cells) in the human retina.
The retina is the back part of the eye where the optic nerve sits. Any information the retina receives from the eyes is relayed to the brain via the optic nerve.
In the May edition of The Lancet, a published research study also shed light on this topic. Using a noninvasive, eye imaging technique called optical coherence tomography (OCT), researchers at the Paulista Institute of Studies and Research in Ophthalmology in Brazil detected damage to the retina and optic nerve in all 12 COVID-19 patients tested.
However, interestingly, these patients experienced no visual impairments.
Later in July, another study was published in the Journal of Medical Virology in which Ophthalmologists at the Hospital Clinico Universitario in San Carlos,Spain performed an OCT scan for five patients with COVID-19. According to the results, increased optic nerve inflammation was noted in all five patients, as compared to the state of their optic nerves prior to COVID-19 exposure.
Similar to the previous study, none of these patients experienced visual impairments. This seems to imply that the optic nerve inflammation they experienced may not have been severe enough to damage the nerve completely.
Important note: The most common early signs of COVID-19 are fever, cough, and shortness of breath — none of which are ocular symptoms.
If you notice any COVID-19 symptoms, seek appropriate medical attention as soon as possible.