Respiratory protection and refractive error: Comment on ‘Staff perceptions of military chemical–biological–radiological–nuclear (CBRN) air-purifying masks during a simulated clinical task in the context of SARS-CoV-2’

We would like to commend Adamson et al. on their very interesting article investigating the feasibility, performance and user experience of a modern military spec full-face air-purifying respirator (APR) in a civilian intensive care unit. ¹ The findings in this context are of great importance in understanding the need for safe, efficient and comfortable respiratory protective equipment (RPE) for frontline healthcare workers during this and future pandemics. The coronavirus disease 2019 (COVID-19) pandemic found most countries unprepared, with limited RPE resources at hand, and healthcare workers had to improvise with RPE designed for industrial, construction or mining applications. We would like to comment on the aspect of vision correction while using APRs, as Adamson et al. had excluded healthcare workers with spectacles. During the COVID-19 pandemic, many healthcare workers with spectacles using non-reusable filtering face pieces struggled with problems of fogging.

Modern full-face APRs are specifically designed to reduce fogging of the eyepieces or visors: ambient air enters through the filter, is first directed over the eyepieces to help prevent misting and then into the oronasal inner mask from which it is inhaled. The moist exhaled air is directed straight out of the outlet valve, avoiding any contact with the inner eyepieces/visor. ²

Our own previous full-face APR studies ³ found equally high comfort levels among medical first responders and receivers. However, like Adamson et al., ¹ we were often limited to only enrol healthcare workers who did not require vision correction or who were able to use contact lenses.

Refractive error is prevalent in the general population. ⁴ The additional impairment from normal age-related presbyopia means that few healthcare workers over the age of 50 years will be glasses-free in a work environment. A pragmatic illustration of the prevalence of functionally important refractive error is the observation that 30/61 individuals (nurses and doctors) working in the three intensive treatment units (ITUs) at St Thomas’ Hospital London on the day of writing used refractive spectacle correction.

Currently, the RPE best suited for users who need sight correction seems to be loose-fitting powered air-purifying respirator (PAPR) hoods, as operators can leave their normal spectacles in place. In conclusion, limited availability of individualised eye correction inserts seems the only logistical downside of full-face APR use. Due to the significant challenges with PAPRs regarding high up-front cost, maintenance, battery dependence, complex decontamination and sanitisation processes and storage, we would like to advise employers to supply healthcare workers with appropriate vision correction, either in the form of optical inserts for aerosol-protecting goggles or optical inserts for full-face APRs.