This prospective cross-sectional study examines the impact of indoor environments on symptoms and signs of dry eye.
Study design
Researchers recruited 97 veterans with a wide range of dry eye metrics from the Miami VA Healthcare eye clinic between October 2013 to August 2018. Eighty-one patients were male with a mean age of 58 years. Dry eye symptoms were in the moderate range with a mean Ocular Surface Disease Index (OSDI) score of 31.2.
The authors first evaluated dry eye metrics in the clinic and then indoor home environmental metrics within 1 week using a handheld particle counter. Indoor environmental metrics included temperature, humidity and air pollution (particulate matter mass and count). To prevent any bias, investigators were masked to questionnaire data.
Outcomes
Humidity was linked to worse symptoms and signs, positively correlating with OSDI score (r=0.30), inflammation (r=0.32), eyelid vascularity (r=0.27) and meibomian gland dropout (r = 0.27), and negatively correlating with Schirmer score (r=-0.25). After adjusting for demographic characteristics, comorbidities, medications and interaction variables, multivariate analyses revealed that particulate matters of 2.5 μm (PM2.5) or smaller correlated with dry eye metrics.
Limitations
Since the study was limited to mostly male patients from a defined veteran population at 1 site, the results may not be generalizable to other groups. The study also excluded patients using ocular medications. In addition, although the particle counter recorded particle number and humidity, the authors' analysis did not take into account other gaseous air pollutants (i.e., carbon monoxide and ozone) and particle composition and type, such as heavy metals and bioaerosols (i.e., mold and pollen)—all factors that can affect the ocular surface synergistically and exacerbate the effects of particulate matter. The associations do not necessarily implicate a cause-and-effect relationship.
Clinical significance
Given the COVID-19 pandemic and need for social distancing, many people are spending more time at home, increasing exposure time to the indoor environment. This study offers a potential therapeutic option to improve and manage dry eye symptoms and signs by decreasing indoor humidity and airborne pollutants, which may improve dry eye signs and symptoms.