What is the efficacy of eye protection equipment compared to no eye protection equipment in preventing transmission of COVID-19-type respiratory illnesses in primary and community care?

April 3, 2020

Lead author: Kamlesh Khunti, University of Leicester

Series editor: Trish Greenhalgh

Contributing authors:
Trish Greenhalgh and Xin Hui Chan, University of Oxford
Quentin Durand-Moreau and Sebastian Straube, University of Alberta, Canada
Declan Devane and Elaine Toomey, Evidence Synthesis Ireland and Cochrane Ireland
Anil Adisesh, University of Toronto, and St. Michael’s Hospital, Toronto, Canada

On behalf of the Oxford COVID-19 Evidence Service Team
Centre for Evidence-Based Medicine
Nuffield Department of Primary Care Health Sciences
University of Oxford

Correspondence to kk22@leicester.ac.uk

VERDICT
There is no direct evidence from randomised trials that eye protection equipment alone prevents transmission of COVID-19. Indirect evidence suggests that healthcare workers’ conjunctivae could be exposed to infective droplets and aerosols from patients during close contact. It is important to assess contagion risk of every encounter and take appropriate precautions   Where close contact is required, guidance for full personal protective equipment should be followed


Most real-world research evaluating the effectiveness of eye protection equipment for biological hazards has been in the context of influenza or other relatively benign respiratory conditions and based in hospitals. There are no published head-to-head trials of eye protection equipment related to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, the virus that causes COVID-19) or trials in primary or community care settings. Current guidance is therefore based on indirect evidence – notably, simulations using data from SARS and MERS outbreaks – as well as expert opinion, custom and practice.

Policy guidance from various bodies (e.g. Public Health England, World Health Organization (WHO)) emphasizes the need to assess the contagion risk of an encounter and use the recommended combination of equipment for that situation. In particular, suitable personal protective equipment (PPE), which typically includes respirator masks, goggles or visor, long-sleeved gown, waterproof aprons have been recommended to protect against small airborne particles in aerosol-generating procedures (AGPs) such as intubation. For non-AGPs, there is no evidence from randomised trials that eye protective equipment provides additional protection. However, evidence emerging in an ongoing review by our group indicates that with close contact, mucous membranes may be explosed to droplets even in the absence of formally classified AGPs.

Whilst patients’ eyes are rarely symptomatic in COVID-19 and conjunctival secretions rarely test positive for the virus, the mucous membranes of the healthcare worker (including eyes) may be exposed to respiratory droplets from the patient.

For this reason, eye protection equipment should be used for primary and community care when assessing patients with possible SARS-CoV-2 infection. Eye protection is most effective when used in combination with other PPE measures in this situation and for protection against any blood or other body fluid splashes that may occur with procedures.

BACKGROUND

Context

Concerns have been raised about the limited PPE provision globally, including for UK primary care staff, with some general practice surgeries, dental surgeries and care homes reporting very limited provision. We were asked to find out whether and in what circumstances lack of eye protection equipment is putting primary care clinicians at risk of contagion compared to use of eye protective equipment such as goggles.

Background

COVID-19 is spread by four means: contact (direct or via a fomite); droplet infection (droplets from the respiratory tract of an infected individual during coughing or sneezing are transmitted onto a mucosal or conjunctival surface of a susceptible individual or onto environmental surfaces to become fomites); via aerosols (particularly during procedures such as intubation); and faeco-oral.[1] [2] It should be noted that in one recent laboratory study, SARS-CoV-2 survived longer than other respiratory viruses when artificially aerosolised.[3]

The outbreak of recently identified SARS-CoV-2 infection has become a world-wide health threat. Currently, information is urgently needed for primary care to understand the transmission, clinical features and methods of infection control of COVID-19. Several concerns have been raised regarding the role of eyes in transmission. The conjunctiva is directly exposed to extraocular pathogens. The mucosa of the ocular surface and the upper respiratory tract is connected by the nasolacrimal duct [4]. Tears and ocular secretions from infected individuals may contain viruses and play a role as a source of spread [4]. However, the infectivity, transmission and clinical importance in the COVID-19 context remains incompletely understood [5] [6]. The prevalence of conjunctivitis with COVID-19 has been reported to be 0.8-4.8% although there are uncertainties in view methods used to confirm positive cases. Conjunctival congestion has been reported by 4.0-5.5%, and conjunctival secretion in 9.0-10.5% of patients at presentation in those with COVID-19.[6]  Other evidence suggests that the eye is rarely involved by COVID-19 infection and conjunctivitis is uncommon in patients with COVID-19 with very low positive viral cultures  from conjunctival scrapings of patients who have tested positive for SARS-CoV-2. However, the eyes of healthcare providers are exposed to respiratory droplets and aerosols from infected patients.

Most guidance on PPE appears skewed to secondary care settings (emergency department or inpatient) settings and focuses mainly on situations and settings deemed ‘high-risk’, for which full PPE including respirator masks are recommended. Whilst it is often assumed that primary and community care settings are ‘low-risk’, in reality the varied case load of primary care will include some activities which involve close contact and expose the healthcare worker to droplets and aerosols.

This review mainly considers the use of eye protective equipment to reduce droplet and aerosol spread via ocular transmission.

A systematic review of 40 studies of the risk of nosocomial respiratory syncytial virus (RSV) infection suggested that eye protection was more effective than gowns and masks, however it was not possible to assess the effectiveness of individual components of control measures [7]. However, most studies made some use of PPE (which included gowns, gloves, surgical or respirator masks, goggles) and were conducted in neonatal and paediatric settings.  In the systematic review, two studies in which staff eye protection was used (eye–nose goggle or goggles plus masks) found this to be effective in preventing transmission of infection to staff.

Close eye examinations and ophthalmoscopy should be avoided if possible during an outbreak of COVID-19, but in some cases these procedures may still be necessary. Where close contact is required, eye protection equipment should be used as part of a full PPE.

The WHO has produced technical specifications for these items, based on simulation exercises using data from past SARS and MERS outbreaks. Importantly, goggles should not be considered as isolated interventions. Other protection includes hand hygiene, surgical or respirator masks, aprons or gowns, and gloves [1, 8, 9].

CURRENT EVIDENCE

Current guidance

Official UK guidance released in February 2020 suggest that eye/face protection should be used when there is a risk of contamination to the eyes from splashing secretions, blood, body fluids or excretions. The guidance recommends eye/face protection using any of one of the following: surgical mask with integrated visor; full face shield/visor; polycarbonate safety spectacles or equivalent[1] . The guidance also states that regular corrective spectacles are not considered adequate eye protection.

The WHO has stated that human-to-human transmission has been documented, including in healthcare workers, and AGP may play a role in the spread of the disease [8].The WHO distinguishes four situations with three different levels of risk:

  • Triage (lowest risk: requires hand hygiene + surgical mask)
  • Suspected or confirmed case of COVID-19 requiring healthcare facility admission and no AGP (intermediate risk: requires hand hygiene, surgical mask, gown, goggles, gloves)
  • Suspected or confirmed case of COVID-19 requiring healthcare facility admission and AGP (high risk: requires hand hygiene, respirator mask, gown, goggles, gloves)
  • Collection of specimens for laboratory diagnosis (high risk: requires hand hygiene, respirator mask, gown, goggles, gloves)

SEARCH STRATEGY

We conducted a brief search of Medline and Cochrane library without date restrictions. We also conducted searches of Google Scholar. We used the following key words “Eye Protective Devices”[Mesh] OR goggle*[tw] OR “visor”[tw] OR “facial protection equipment”[tw] OR “safety glass”[tw] OR “safety glasses”[tw] OR “safety spectacles”[tw] combined with influenza [tw[ OR exp Influenza [Mesh] OR Coronavirus Infections [Mesh] OR Coronavirus [Mesh] OR coronavirus [tw] OR COVID [tw] OR SARS Virus [MESH] sars [TW] OR Severe Acute Respiratory Syndrome [MESH] OR mers [tw] OR Middle East Respiratory Syndrome Coronavirus [Mesh] OR respiratory infection [tw] OR Respiratory Tract Infections [Mesh] combined with “respiratory tract infections”, “randomized controlled trial” and “systematic review”.

We identified 52 randomised controlled trials and 12 systematic reviews on Medline. Overall from our searches, we idensified 2 reviews that were relevant to our question.

Critical appraisal of the two systematic reviews

Verbeek et al. 2019 [10]

Evaluation against the AMSTAR II checklist, we judged the review to be of good quality.

This Cochrane Review of PPE for preventing highly infectious diseases due to exposure to contaminated body fluids in healthcare staff included 17 studies with 1950 participants evaluating 21 interventions. The review found that there were no eligible studies on the effects of goggles or face shields. This review is currently being updated and we will update the results once the updated review is published (expected date  April 2020)

French et al. 2016[7]:

Evaluation against the AMSTAR II checklist, we judged the review to be of good quality.

Forty studies were included. RSV transmission risk varied by hospital setting. Most studies (= 13) employed multi‐component interventions (e.g. cohort nursing, PPE, isolation), and these were largely reported to be effective in reducing nosocomial transmission. Four studies examined staff PPE; eye protection appeared more effective than gowns and masks however it was not possible to assess the effectiveness of individual components of control measures. Overall, risk of bias for included studies tended to be high. The review concluded that RSV transmission risk varied widely during hospital outbreaks. Although multi‐component control strategies appear broadly successful, further research is required to disaggregate the effectiveness of individual components.

Disclaimer:  the article has not been peer-reviewed; it should not replace individual clinical judgement and the sources cited should be checked. The views expressed in this commentary represent the views of the authors and not necessarily those of the host institution, the NHS, the NIHR, or the Department of Health and Social Care. The views are not a substitute for professional medical advice. A limitation is that because of time constraints, only one person screened the studies.

AMSTAR II checklist – Verbeek et al. 2019:

  1. Did the research questions and inclusion criteria for the review include the components of PICO? Yes
  2. Did the report of the review contain an explicit statement that the review methods were established prior to conduct of the review and did the report justify any significant deviations from the protocol? Yes
  3. Did the review authors explain their selection of the study designs for inclusion in the review? Yes
  4. Did the authors use a comprehensive literature search strategy? Yes
  5. Did the authors perform study selection in duplicate? Yes
  6. Did the authors perform data extraction in duplicate? Yes
  7. Did the review authors provide a list of excluded studies and justify the exclusions? Yes
  8. Did the authors describe the included studies in adequate detail? Yes
  9. Did the review authors use a satisfactory technique for assessing the risk of bias (RoB) in individual studies that were included in the review? Yes
  10. Did the review authors report on the sources of funding for the studies included in the review? Yes
  11. If meta-analysis was justified did the review authors use appropriate methods for statistical combination of results? Yes
  12. If meta-analysis was performed did the review authors assess the potential impact of RoB in individual studies on the results of the meta-analysis or other evidence synthesis? Yes
  13. Did the review authors account for RoB in individual studies when interpreting/ discussing the results of the review? Yes
  14. Did the review authors provide a satisfactory explanation for, and discussion of, any heterogeneity observed in the results of the review? Yes
  15. If they performed quantitative synthesis did the review authors carry out an adequate investigation of publication bias (small study bias) and discuss its likely impact on the results of the review? No – publication bias not discussed
  16. Did the review authors report any potential sources of conflict of interest, including any funding they received for conducting the review? Yes

AMSTAR II checklist – French et al. 2016:

  1. Did the research questions and inclusion criteria for the review include the components of PICO? Yes
  2. Did the report of the review contain an explicit statement that the review methods were established prior to conduct of the review and did the report justify any significant deviations from the protocol? Yes
  3. Did the review authors explain their selection of the study designs for inclusion in the review? No – not particularly clear what study designs eligible, or rationale behind study design inclusion
  4. Did the authors use a comprehensive literature search strategy? Yes
  5. Did the authors perform study selection in duplicate? Yes
  6. Did the authors perform data extraction in duplicate? Yes
  7. Did the review authors provide a list of excluded studies and justify the exclusions? No – reasons given for full text exclusion, but list of excluded references not provided
  8. Did the authors describe the included studies in adequate detail? Yes
  9. Did the review authors use a satisfactory technique for assessing the risk of bias (RoB) in individual studies that were included in the review? Yes
  10. Did the review authors report on the sources of funding for the studies included in the review? No
  11. If meta-analysis was justified did the review authors use appropriate methods for statistical combination of results? N/A – meta analysis not justified or conducted
  12. If meta-analysis was performed did the review authors assess the potential impact of RoB in individual studies on the results of the meta-analysis or other evidence synthesis? N/A – meta analysis not justified or conducted
  13. Did the review authors account for RoB in individual studies when interpreting/ discussing the results of the review? Yes
  14. Did the review authors provide a satisfactory explanation for, and discussion of, any heterogeneity observed in the results of the review? Yes
  15. If they performed quantitative synthesis did the review authors carry out an adequate investigation of publication bias (small study bias) and discuss its likely impact on the results of the review? N/A – narrative synthesis conducted only
  16. Did the review authors report any potential sources of conflict of interest, including any funding they received for conducting the review? Yes

REFERENCES

  1. Official Guidance, COVID-19: Guidance for infection prevention and control in healthcare settings. Version 1.0. 2020. Accessed 21.3.20 at https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/874316/Infection_prevention_and_control_guidance_for_pandemic_coronavirus.pdf.: Department of Health and Social Care (DHSC), Public Health Wales (PHW), Public Health Agency (PHA) Northern Ireland, Health Protection Scotland (HPS) and Public Health England
  2. Ong, S.W.X., et al., Air, Surface Environmental, and Personal Protective Equipment Contamination by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) From a Symptomatic Patient. JAMA, 2020.
  3. van Doremalen, N., et al., Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. New England Journal of Medicine, 2020.
  4. Chuan-bin Sun, Y.-y.W., Geng-hao Liu, Zhe Liu, Role of the eye in transmitting human coronavirus: what we know and what we do not know. 2020.
  5. Organisation, W.H., Update 27 – One month into the global SARS outbreak: Status of the outbreak and lessons for the immediate future. 2003.
  6. Chen, L., et al., Ocular manifestations and clinical characteristics of 534 cases

of COVID-19 in China: A cross-sectional study 2020.

  1. French, C.E., et al., Risk of nosocomial respiratory syncytial virus infection and effectiveness of control measures to prevent transmission events: a systematic review. Influenza Other Respir Viruses, 2016. 10(4): p. 268-90.
  2. World Health Organisation, Requirements and technical specifications of personal protective equipment (PPE) for the novel coronavirus (2019-ncov) in healthcare settings. 2020. Accessed 21.3.20 at https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=2ahUKEwjS2di4-q3oAhVXh1wKHWeGDvEQFjACegQIARAB&url=https%3A%2F%2Fwww.paho.org%2Fen%2Ffile%2F59297%2Fdownload%3Ftoken%3Dbr2NtqhR&usg=AOvVaw1Sicp3C6m3fjFmMfIeox7R, Geneva.
  3. Public Health England, When to use a face mask or FF£ respirator. 2020. Accessed 21.3.20 at https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/874310/PHE_11606_When_to_use_face_mask_or_FFP3_02.pdf, London.
  4. Verbeek, J., et al., Personal protective equipment for preventing highly infectious diseases due to exposure to contaminated body fluids in healthcare staff. Cochrane Database Syst Rev., 2019.