A lot of attention has been placed on the use of face coverings to limit COVID-19 transmission, but there has been less focus on ocular involvement and ocular protection strategies. The author reviews the literature and discusses possible solutions.
The COVID-19 outbreak has been declared a pandemic by the World Health Organization (WHO) [1]. The global impact of COVID-19 is unprecedented in modern times. As of 21 May 2020, the WHO has reported 4.9 million cases globally and over 320,000 deaths [2]. By early April, 3.9 billion people globally were under a government enforced lockdown of some form, representing over half the world’s population [3].
The International Monetary Fund (IMF) have estimated that revenue measures and government spending globally through mid-April 2020 has reached $3.3 trillion to sustain economic activity, with an additional $4.5 trillion in loans, guarantees and equity injections [4].
The causative novel human coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), possesses a high transmission efficiency with reported reproductive numbers higher than that of the 2009 H1N1 influenza virus [5,6]. SARS-CoV-2 is primarily transmitted by respiratory droplet spread, direct contact and can also survive in air [7,8]. The virus can be transmitted by asymptomatic carriers [9]. Thus, it is of paramount importance that effective public health policies are employed to limit human-to-human transmission, including hand hygiene, self-isolation and social distancing [1,10].
“Ocular features can be the first or indeed only features seen in COVID-19”
There has been significant attention on the role of facemasks and face coverings to limit droplet spread of SARS-CoV-2, but less attention on ocular involvement and the importance of eye protection [11,12]. This review aims to analyse the literature of ocular involvement in COVID-19, followed by a discussion of protective strategies for the general public and healthcare professionals.
Ocular involvement
A number of ocular manifestations of COVID-19 have been described [13,14]. In the landmark paper by Guan et al. describing clinical characteristics of COVID-19 in China, nine (0.8%) of 1,099 patients from 552 hospitals in China were reported to have conjunctival congestion (redness) [15].
More recently, the largest ophthalmology-specific study by Wu et al. reported ocular symptoms in 12 (31.6%) of 38 patients admitted to hospital for treatment of COVID-19 [16]. These included chemosis (seven patients), epiphora (seven patients), increased secretions (seven patients) and hyperaemia (three patients). Significantly, one patient presented with epiphora as their first presenting symptom of COVID-19. Of the 12 patients with eye symptoms, two patients (16.7%) had positive conjunctival swab results for SARS-CoV-2 on reverse-transcriptase polymerase chain reaction (RT-PCT). Interestingly in the blood test results, Wu et al. observed that inflammatory markers including white cell count, neutrophil count and C-reactive protein were found in higher levels in those patients with eye symptoms. There is significant correlation between these inflammatory markers and disease severity [17].
Scalinci et al. reported a case series of five patients with conjunctivitis as the sole presenting sign of COVID-19 [18]. All five were diagnosed with COVID-19 confirmed by naso-pharyngeal swabs using RT-PCR. Surprisingly, none of the five patients developed the typical symptoms of fever or cough, thus conjunctivitis remained the sole manifestation throughout their illness.
Xia et al. reported that one (3.3%) out of 30 patients hospitalised with COVID-19 had viral conjunctivitis [19]. This patient had no severe fever or respiratory symptoms at the time of testing, yet they tested positive for SARS-CoV-2 in two samples of tears and conjunctival secretions using RT-PCT. Similarly, Seah et al. reported one (5.8%) out of 17 patients developed conjunctival injection and chemosis whilst hospitalised [20].
In addition, there have been several published case reports of ocular involvement in COVID-19 [21-24]. Reported findings include redness, tearing, foreign body sensation, lid swelling, palpebral conjunctival follicles and keratitis [21,22]. Navel et al. reported late (>2 weeks) eye complications including tarsal haemorrhages, mucous filaments and tarsal pseudomembranes [23]. In addition, Salducci et al. reported a case of severe bilateral conjunctivitis with secretions, chemosis, pseudomembranes and associated preauricular lymph node swelling and enlarged submaxillaries.
Protective strategies
The eye is an important site of entry for potential pathogens [14]. Transmission could be direct, such as from sneezing or coughing into the eyes, or indirect, such as transferral from infected surfaces to the eyes via the hands. It is currently unclear whether ocular exposure alone could confer COVID-19, but one possible mechanism could be drainage via the nasolacrimal duct to the respiratory tract [25]. In their article supporting the use of facemasks or face coverings for the public, Greenhalgh et al. suggest application of the ‘precautionary principle’ – “a strategy for approaching issues of potential harm when extensive scientific knowledge on the matter is lacking” [11]. The same principle could reasonably be applied for protecting the eyes from potential infection. The following are protective strategies for the general public and healthcare professionals to reduce the risk of eye infection.
Practice hand hygiene and social distancing
The Centers for Disease Control and Prevention (CDC) have recommended frequent hand washing using soap and water for at least 20 seconds, particularly after touching the face, sneezing or coughing [10]. This is echoed by the American Academy of Ophthalmology (AAO) and Royal College of Ophthalmologists (RCOphth) [26,27]. Where soap and water are not available, the CDC recommend hand sanitiser containing at least 60% alcohol. The CDC advise the use of face coverings for the general public, a recommendation echoed by Greenhalgh et al. [10,11]. Coughs and sneezes should be covered by the face covering when in public, or a tissue or inner elbow followed by hand washing. The CDC advise against touching the eyes or face with unwashed hands. Importantly, social distancing should be practised with a minimum distance of six feet from other people to minimise the risk of transmission. Even while social distancing or isolating, patients should continue to seek medical attention for any urgent eye issues such as eye injuries, reduction or loss of vision [26].
Avoid eye rubbing
The AAO have warned against eye rubbing, as this increases the risk of transferring virus from infected hands to the eyes [26]. If this urge is due to dryness, then lubricating eye drops can be used to alleviate dry eye symptoms. Hand washing should be performed before and after applying eye drops. If the urge to rub the eyes cannot be overcome, the AAO recommend the use of a clean tissue followed by hand washing.
Switch contact lenses to glasses
For contact lens wearers, the American Academy of Ophthalmology (AAO) recommend a rigorous hygiene protocol when applying contact lenses [28]. Currently there is no evidence that contact lens wearers are at increased risk of contracting COVID-19. However, in light of the COVID-19 pandemic, the AAO have recommended switching from contact lenses to spectacles wherever possible [26].
The AAO argue that contact lens wearers tend to touch their eyes more frequently, increasing the risk of accidental transfer of virus particles from the hands to the eyes. Furthermore, wearing glasses may add an additional layer of protection against respiratory droplets, as well as limiting eye touching or rubbing. It should be noted that conventional glasses do not fully protect against the virus entering the eyes, unlike properly fitted goggles or face shields.
Should eye protection be used by the public?
The WHO have recommended eye protection (goggles or face shield) for healthcare workers at risk of SARS-CoV-2 transmission via close contact or aerosol generating procedures (AGPs) [29]. However, a recent review by Khunti et al. concluded that there is “no direct evidence from randomised trials that eye protection equipment alone prevents transmission of COVID-19”, but it is still important to take precautions as healthcare workers’ eyes could be exposed to infective droplets or aerosols during close contact [30].
“The eye is an important site of entry for potential pathogens”
With regards to the general public, there is no evidence supporting the widespread use of goggles or other eye protection. The AAO state that safety goggles offer defence for those caring for a sick patient or potentially exposed person, but they have not recommended the widespread use of goggles for the public. Applying the precautionary principle, safety goggles are relatively low cost with no direct harm conveyed to the user, yet they may confer additional protection against potential COVID-19. Thus, it may be reasonable for members of the general public to use safety goggles in addition to face coverings, especially in enclosed spaces such as public transport if this is unavoidable.
Other measures for healthcare professionals
Eye protection, such as goggles and face shields, are recommended by the WHO, along with full personal protective equipment (PPE) such as medical masks, gowns and gloves, with specific recommendations according to role and procedures undertaken [29]. In addition, special breath shields have been recommended for ophthalmologists as a physical barrier against small virus particles, but these must be carefully disinfected between patients [31]. Appropriate handwashing and disinfecting of the clinical environment is crucial. Face-to-face patient contact should be minimised to only essential or critical activities, with telemedicine (remote patient care via video or telephone) practised wherever possible [14]. Triage systems can be implemented at the ‘front door’ to screen for common COVID-19 symptoms or risk factors, such as recent travel or contact with infected individuals [14]. Staff reorganisation into separate teams for COVID-19 and non-COVID-19 areas, sometimes called ‘hot’ and ‘cold’ sites, have been suggested and implemented widely [14]. Waiting rooms should be kept as empty as possible through prioritising urgent appointments only, optimising patient flow and spacing chairs six feet apart to facilitate social distancing [14].
Conclusions
The eye is an important site of entry for potential pathogens. There are numerous studies and case reports of ocular manifestations of COVID-19, but no conclusive evidence that sole ocular exposure can lead to COVID-19. However, some studies have demonstrated SARS-CoV-2 found in tears and conjunctival secretions. Importantly, ocular symptoms may be the first or indeed only symptoms in infected patients. General risk reduction strategies include good hand hygiene, social distancing and operational measures in hospitals. Strategies specifically to reduce the risk of eye infection include eye protection, avoidance of eye rubbing, including the safe use of eye lubricants where appropriate, handwashing before applying eye drops and switching from contact lenses to glasses wherever possible.
Declaration of competing interests: None declared.
Acknowledgements
Dr Sohaib Rufai is funded by a National Institute for Health Research (NIHR) Doctoral Fellowship. The views expressed in this article are those of the author and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.
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