In many regions of the northern hemisphere, the beginning of fall ushers in the onset of colder, drier weather, which exacerbates dry eye-related signs and symptoms for many who have dry eye (van Setten et al, 2016). Seasonality, defined by the Cambridge Dictionary as “the state or quality of being seasonal or dependent on the seasons,” is a common finding in many conditions including systemic allergies and influenza (Naumova, 2006). These issues may also be further complicated and exacerbated by both indoor and outdoor air pollution including particulate matter (Mandell et al, 2020).

Dry eye disease (DED) is an increasingly frequent, chronic disease characterized by inflammation, loss of homeostasis of the ocular surface, and reduced secretion by the lacrimal and meibomian glands (Mandell et al, 2020). Particulate matter in the form of air pollution has been identified as contributory to the genesis of DED (Galor et al, 2014). The amount of particulate matter in the atmosphere is defined as aerosol optical depth (AOD) and is an indicator of the concentration of aerosols (solid and liquid particles) suspended in the atmosphere.

How Significant Is the Impact?

Outdoor Pollution In a study designed to evaluate the impact of environmental particulate matter on DED, Galor et al (2014) retrospectively evaluated the records of all patients (3.41 million) seen in one of the 394 VA eye clinics within the continental United States between July 5, 2006 and July 4, 2011. A total of 606,708 patients received an ICD-9 diagnosis of dry eye (375.15) and were prescribed medication or underwent a procedure for the condition. The researchers then accessed the meteorological records for the location in which each patient lived and evaluated several weather-related variables in the location where each subject lived. These variables included AOD, atmospheric pressure, wind speed, temperature, relative humidity, visibility, latitude, and longitude (Galor et al, 2014).

Their study revealed several important findings. Air pollution (as measured by AOD) and atmospheric pressure surfaced as the two most significant risk factors for dry eye, while elevated humidity and increased wind speed were inversely associated with the risk of DED. Metropolitan areas, including New York City, Chicago, Los Angeles, and Miami, showed relatively high concentrations of AOD and higher rates of DED compared to less heavily populated areas (Galor et al, 2014).

The presence of particulate matter in the atmosphere has implications beyond eye care. Adebiyi and Kok (2020) recently reported that levels of coarse mineral dust in the atmosphere are actually four times higher than previous estimates, which impacts clouds, ocean ecosystems, and climate. Coarse mineral dust is a major component of Earth’s atmosphere and factors into global temperature, with greater levels of dust resulting in a greater warming effect.

Indoor Pollution Huang et al (2020) performed a prospective cross-sectional study of 97 veterans from the Miami Veterans Affairs Healthcare eye clinic. Indoor environmental metrics, including temperature, humidity, and particulate matter mass and count, were initially evaluated in the clinic and then within one week by indoor home environmental metrics using a handheld particle counter. The researchers concluded that after adjusting for humidity, increased exposure to particulate matter was associated with worse dry eye metrics, impacting Ocular Surface Disease Index scores, Schirmer’s scores, meibomian gland dropout, and inflammation.

In summary, primary care physicians and eyecare professionals need to be aware of the association between environmental conditions and DED and should elicit an environmental history when assessing DED patients. Furthermore, environmental manipulations, so far as is possible, such as increasing residence/workplace humidity and decreasing exposure to air pollution, should be considered as part of the overall management of DED patients. CLS

For references, please visit www.clspectrum.com/references and click on document #311.