Dry Eye Syndrome Linked to Poor Air Quality, Weather

Jennifer Garcia

March 04, 2014

Air pollution and atmospheric pressure are the most influential environmental risk factors for the development of dry eye syndrome (DES), according to a new report published online February 24 in Ophthalmology.

As part of a retrospective analysis, researchers evaluated 606,708 patients with DES seen at 1 of 394 Veterans Affairs (VA) eye clinics in the United States between July 5, 2006, and July 4, 2011. Clinical data were collocated by Zip code, and meteorological data, including visibility and aerosol optical depth (AOD, a surrogate marker for air pollution), were evaluated for each facility during the study period.

The researchers, led by Anat Galor, MD, MSPH, from the Bascom Palmer Eye Institute at the University of Miami, Florida, found that the risk for DES was 13% higher for patients in Zip codes where the atmospheric pressure was more than 1 standard deviation higher than the mean (incidence rate ratio [IRR], 1.131; 95% confidence interval [CI], 1.129 - 1.133; P < .001).

In addition, those patients exposed to the highest levels of air pollution (as measured by AOD) had the greatest risk (IRR, 1.126; 95% CI, 1.125 - 1.127; P < .001). In contrast, "[h]igher humidity and wind speed were inversely associated with the risk of DES (IRR, 0.927 [95% CI, 0.926–0.927] and IRR, 0.938 [95% CI, 0.937–0.939], respectively; P < 0.001)."

"It's actually pretty challenging to combine environmental data and health data," Dr. Galor told Medscape Medical News. These data are recorded separately and at different time scales, but Dr. Galor notes by retrospectively accessing meteorologic data and combining it with health data, "we were able to show that, looking at the continental United States, the diagnosis of dry eye and the risks of having that diagnosis were really associated with conditions that we thought would be important."

AOD is "an indicator of the concentration of aerosols (solid and liquid particles suspended in the air)," so veterans living in metropolitan areas with high AOD concentrations are "3 to 4 times more likely to be diagnosed with DES compared with less urban areas with relatively low concentrations of AOD," Dr. Galor and colleagues write. The authors also found that northern and eastern geographic areas had the highest levels of DES cases compared with southern and western areas.

"I think that this is really exciting, but I think that this isn't the end of the story because there are a lot of other things we want to know," Dr. Galor said. "For example, these data monitor outdoor pollution and outdoor environmental conditions, but we spend over 90% of our time indoors. Evaluating the sum of indoor and outdoor environmental exposures and how they affect dry eye status I think will be another exciting avenue of future study," she said.

Christopher J. Rapuano, MD, chief of the cornea service at the Wills Eye Institute, Philadelphia, Pennsylvania, told Medscape Medical News: "This study confirms what other smaller studies have shown." However, "[t]his study is different from many others in that it is very large and looked at more atmospheric data."

The study authors acknowledge limitations such as the retrospective nature of the data and the inability to determine cause and effect relationships as well as the lack of tear parameter data in making the diagnosis of dry eye disease.

Dr. Rapuano, who was not associated with the study, notes that although the study identified possible risk factors for dry eye disease, "you still need to treat the patient based on their particular signs and symptoms." For example, he explained, "If your office is in a location with lower humidity and higher air pollution, more of your patients will probably have dry eye symptoms, and you should be aware of that. On the flip side, if your office is in a location with high humidity and lower air pollution, your patient may still have dry eyes and you still need to treat it."

"Environmental manipulation for patients with DES makes sense, but we don't have a lot of data to back up that implementing environmental interventions affects dry eye morbidity," Dr Galor said. Until we have more data, he suggests that environmental manipulation is a commonsense and inexpensive way to attempt to decrease reliance on medication.

The authors and independent commentator have disclosed no relevant financial relationships.

Ophthalmology. Published online February 24, 2014.

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