Dry Eye Dx and Tx

The Impact of Environment on Dry Eye Disease

BY WILLIAM TOWNSEND, OD, FAAO

The introduction of electronic medical records (EMR) has been challenging and costly (Shekelle et al, 2006), but one unmistakable benefit of this technology is the ability to glean large volumes of data that help us track trends in health care (Dungey et al, 2016). Dry eye disease (DED) is ubiquitous and may significantly impact quality of life, but the specific environmental conditions and risks factors that promote it are poorly or incompletely understood (Paulsen et al, 2014).

Accessing and analyzing a large EMR base allows researchers to identify specific environmental and health factors that contribute to development of a disease. This article looks at studies that evaluated the Veterans Affairs (VA) Medical Centers’ EMR to identify environmental factors that contribute to DED development.

What Data Were Examined

Gaylor et al (2014) analyzed the EMR of 3.41 million patients seen in one of 394 VA eye clinics within the continental United States between July 5, 2006, and July 4, 2011. Using 375.15, the ICD-9 code for dry eye syndrome (DES), they identified 606,708 individuals diagnosed and treated for dry eye. The authors also accessed environmental data for the same time period from the National Climatic Data Center and NASA. Their analysis of the cumulative data revealed several important links between the environment and DES.

Air Pollution Aerosol optical depth (AOD) measures the concentration of aerosols and is a precise method of analyzing air pollution. Elevated AOD was strongly associated with DES and was most common in metropolitan areas.

The mechanism by which air pollution impairs the ocular surface is incompletely understood. Wollkoff (2010) reported that the presence of atmospheric pollutants contributes to the dissolution of the pre-corneal tear film, specifically the lipid layer. This may also contribute to dry eye by chronic stimulation of the trigeminal nerve.

Atmospheric Pressure This is the pressure exerted by the weight of air in the atmosphere and is higher at lower altitudes. It was the second factor most strongly associated with DES. The incidence of DES was 13% higher in localities where atmospheric pressure was 1 standard deviation higher than the mean. Many metropolitan areas such as New York, Chicago, Houston, and Miami have high atmospheric pressure and elevated AOD.

Non-Factors Wind speed and higher humidity were inversely proportional to the risk of dry eye.

Geography Evaluation of the geographic distribution of dry eye in VA populations demonstrates a higher incidence in subjects living in the northern and eastern United States, as compared with individuals who reside in the southern and western regions.

In Summary

One potential issue with this data is gender; only 8% of VA patients are females (www.va.gov/vetdata/docs/quickfacts/Population_slideshow.pdf); in dry eye studies of the general population, the incidence of DES, especially those related to autoimmune disease, is significantly higher in females (Brandt et al, 2015).

Practitioners should be aware that DES incidence varies significantly based on local climate, altitude, air pollutants, and geography and should factor that into screening and evaluation for dry eye conditions. CLS

For references, please visit www.clspectrum.com/references and click on document #245.

Dr. Townsend practices in Canyon, Texas, and is an adjunct professor at the University of Houston College of Optometry. He is president of the Ocular Surface Society of Optometry and conducts research in ocular surface disease, lens care solutions, and medications. He is also a consultant or advisor to Alcon, Allergan, NovaBay, TearScience, TearLab, and Science Based Health. Contact him at drbilltownsend@gmail.com.