Study finds increased air pollution leads to surge in daily eye clinic visits

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The number of daily patient visits at the Sue Anschutz-Rodgers Eye Center significantly rise when ambient particulate matter (PM) levels in the Denver metro region increase, according to a study conducted by ophthalmology researchers at the University of Colorado School of Medicine.

The research team noted the World Health Organization has declared climate change to be “the single biggest health threat facing humanity,” yet there are limited studies on the impact of climate change-related air pollution on ocular health.¹

Analyzing more than 144,000 visits for ocular surface irritation and allergy at the center between October 2015 and January 2023, a team of researchers found that patient visits more than doubled during periods of elevated particulate matter from air pollution.

This research, published in Clinical Ophthalmology, highlights a potential association between climate conditions and ocular health.²

“There are many ways climate factors affect health, but the eye is the organ studied the least in this context,” according to lead author Jennifer Patnaik, PhD, MHS, an assistant professor of ophthalmology and epidemiology. “We aimed to expand upon the limited research available and deepen understanding in this area.”

The climate-eye link

Although underexplored, ophthalmologists recognize that environmental factors significantly influence eye health. The ocular surface is directly exposed to the environment, rendering it susceptible to airborne pollutants such as particulate matter.

“These pollutants can destabilize the tear film, cause inflammation, and worsen preexisting conditions like dry eye and allergies, especially in urban and industrialized areas,” said senior author Malik Kahook, MD, professor and Slater Family Endowed Chair in Ophthalmology.

The study focused on particulate matter measuring 10 micrometers or smaller (PM10) and 2.5 micrometers or smaller (PM2.5), both of which are known to adversely affect health.²

“Pollutants such as PM10 and PM2.5 can adhere to the ocular surface, disrupting the tear film and initiating inflammation,” said Kahook, who also serves as vice chair of translational research in the Department of Ophthalmology. “Additionally, many of these particles contain toxic chemicals that activate oxidative stress pathways, causing further damage to sensitive ocular tissues.”

The researchers observed that daily visits to the clinic increased 2.2-fold when PM10 concentrations reached 110 micrograms per cubic meter (µg/m³), a level within the Environmental Protection Agency's established maximum containment limits for PM10.

Studying both PM10 and PM2.5 is crucial, the researchers noted, because the two pollutants affect health differently.

“PM10, being larger, primarily irritates the ocular surface directly, especially in colder temperatures, as our study findings suggest,” Kahook explained. “In contrast, PM2.5, which is smaller, penetrates deeper into tissues and has a broader systemic inflammatory potential. Comparing these pollutants clarifies their distinct roles in ocular health.”

Implications for research, clinical practice

The researchers identified a gradient effect: as particulate matter concentrations increased, so did patient visit counts. Patnaik emphasized the importance of this finding.

“Establishing this kind of dose-response relationship is challenging with smaller datasets,” she said. “However, it strengthens the credibility of our findings and suggests a robust association between air pollution and ocular health.”

The researchers noted that additional research in this field is needed, with the incorporation of more pollutant types, larger population sizes, and broader geographic areas. Patnaik and her team plan to extend their research beyond Denver, exploring national and global datasets to account for regional differences in pollution. She noted that broader data could reinforce the connection and inform policies aimed at improving ocular and overall health.

The findings also have practical implications for clinical care. By monitoring pollution levels, ophthalmologists can anticipate patient surges during high-pollution periods and tailor treatment recommendations accordingly. Educating patients about air quality can encourage proactive use of treatments such as artificial tears, anti-allergy medications, and protective eyewear.

“This research highlights the importance of considering environmental factors when diagnosing and managing ocular surface conditions,” Kahook concluded. “Integrating air quality awareness into clinical practice can enhance patient education and improve treatment outcomes.”

Reference

1.World Health Organization. Climate Change and Noncommunicable diseases: Connections. www.who.int. Published November 2, 2023. Accessed December 6, 2024. https://www.who.int/news/item/02-11-2023-climate-change-and-noncommunicable-diseases-connections

2. Patnaik JL, Dye-Robinson A, James KA, Kahook MY. Association Between Particulate Matter Pollutants and Ophthalmology Visits for Ocular Surface Irritation and Allergy. Clin Ophthalmol. Published November 13, 2024. Accessed December 6, 2024. 18:3263-3270. doi: 10.2147/OPTH.S485199. PMID: 39555215; PMCID: PMC11569711.