Glasses and risk of COVID-19 transmission - analysis of the Virus Watch Community Cohort study
Authors: Navaratnam Annalan M D , O’Callaghan Christopher , Beale Sarah , Nguyen Vincent , Aryee Anna , Braithwaite Isobel , Byrne Thomas E , Fong Wing Lam Erica , Fragaszy Ellen , Geismar Cyril , Hoskins Susan , Kovar Jana , Patel Parth , Shrotri Madhumita , Weber Sophie , Yavlinsky Alexei , Aldridge Robert W , Hayward Andrew C 
Published: April 2022

Background

Respiratory viruses, including SARS-CoV-2, can infect the eyes or pass into the nose via the nasolacrimal duct. The importance of transmission via the eyes is unknown but might plausibly be reduced in those who wear glasses. Previous studies have mainly focussed on protective eyewear in healthcare settings.

Methods

Participants from the Virus Watch prospective community cohort study in England and Wales responded to a questionnaire on the use of glasses and contact lenses. This included frequency of use, purpose, and likelihood of wearing a mask with glasses. Infection was confirmed through data linkage with Second Generation Surveillance System (Pillar 1 and Pillar 2), weekly questionnaires to self-report positive polymerase chain reaction or lateral flow results, and, for a subgroup, monthly capillary blood testing for antibodies (nucleocapsid and spike). A multivariable logistic regression model, controlling for age, sex, income and occupation, was used to identify odds of infection depending on the frequency and purpose of using glasses or contact lenses.

Findings

19,166 Virus Watch participants responded to the questionnaire, with 13,681 (71.3%, CI 70.7-72.0) reporting they wore glasses. A multivariable logistic regression model showed a 15% lower odds of infection for those who reported using glasses always for general use (OR 0.85, 95% 0.77-0.95, p = 0.002) compared to those who never wore glasses. The protective effect was reduced in those who said that wearing glasses interfered with mask wearing. No protective effect was seen for contact lens wearers.

Interpretation

People who wear glasses have a moderate reduction in risk of COVID-19 infection highlighting the importance of the eye as a route of infection. Eye protection may make a valuable contribution to the reduction of transmission in community and healthcare settings.

Funding

The research costs for the study have been supported by the MRC Grant Ref: MC_PC 19070 awarded to UCL on 30 March 2020 and MRC Grant Ref: MR/V028375/1 awarded on 17 August 2020. The study also received $15,000 of Facebook advertising credit to support a pilot social media recruitment campaign on 18th August 2020. The study also received funding from the UK Government Department of Health and Social Care’s Vaccine Evaluation Programme to provide monthly Thriva antibody tests to adult participants. This study was supported by the Wellcome Trust through a Wellcome Clinical Research Career Development Fellowship to RA [206602]. Funding from the HSE Protect study, GOSH Children’s Charity and the Great Ormond Street Hospital BRC supported the involvement of CO in the project.

Research in context

Evidence before the study

Despite the risk of SARS-CoV-2 transmission via the eyes, very few countries have advocated eye protection to reduce transmission amongst the public and, except when providing close care for those known or suspected to be infected, is variable and based on case-by-case assessment of exposure risk. The mechanism, but not the extent, of the transmission route through the eyes is well described in the literature, with several studies reporting detection of SARS-CoV-2 RNA in the tear film, conjunctiva and conjunctival sac. There have been a small number of hospital based observational studies suggesting that eye protection may help prevent COVID-19 infection. A literature search was carried out on 23rd February 2022 across Medline and Embase using the search terms ‘eyewear’, ‘glasses’, ‘SARS-CoV-2’, ‘COVID-19’, ‘SARS’, ‘transmission’ and ‘infectivity’, providing 105 manuscripts. Of these, only eight investigated the risk of infection associated with eye protection, all in hospital settings or followed a cohort of healthcare workers. Among the studies was a systematic review that identified 5 observational studies from 898 articles that were screened. The cohort study with the largest sample size, 345 healthcare professionals, demonstrated a relative risk of 10.25 (95% CI 1.28–82.39; P = 0.009) for infection when not using eye protection. No studies of the potential protective effect of glasses wearing, for visual correction, in community settings were identified.

Added value of this study

The Virus Watch study is a prospective community household study across England and Wales. 19,166 participants responded to the monthly questionnaire on glasses and contact lens use, assessing reported frequency, the purpose of use and how likely they were to wear a mask with glasses. Infections were identified in data linked to the Second Generation Surveillance System (Pillar 1 and Pillar 2 testing), weekly surveys seeking self-reports of polymerase chain reaction or lateral flow device results and, in a subset of 11,701, self-collected capillary blood testing for antibodies (nucleocapsid and spike - nucleocapsid antibodies were taken as evidence of prior infection as these are unaffected by vaccination). Our multivariable logistic regression model, controlling for age, sex, household income and occupation, demonstrated 15% lower odds of infection for those who reported always using glasses for general use compared to those who never wear glasses. The protective effect was not observed in those who strongly agreed with the statement, ‘I am less likely to wear a face covering when I have my glasses on because my glasses steam up’. Counterfactual analysis of contact lenses did not suggest a protective effect regardless of frequency of use.

Implications of all the available evidence

The findings of this study demonstrate a moderate reduction in risk of SARS-CoV-2 infection in those who always wear glasses compared to never. Unlike other studies, our results are representative of a community setting, adjust for potential confounders and provide a counterfactual analysis with contact lenses. This extends the current evidence to community settings and validates proposed biological mechanisms of eye protection reducing the risk of SARS-CoV-2 transmission.