Daily visit counts at the Sue Anschutz-Rodgers Eye Center significantly increase when certain ambient particulate matter (PM) levels in the Denver metro region are higher, according to a new study by ophthalmology researchers at the University of Colorado School of Medicine.
In analyzing more than 144,000 ocular surface irritation and allergy visits to the eye center from October 2015 to January 2023, the researchers discovered that visits more than doubled when the particulate matter from air pollution was prevalent.
This research, published in the journal Clinical Ophthalmology, points to a possible association between climate conditions and the eyes.
“There are a lot of ways climate factors impact our health, but the eye is the organ that is the least studied,” says the study’s lead author Jennifer Patnaik, PhD, MHS, assistant professor of ophthalmology and epidemiology “We wanted to build upon the little bit of research that exists and expand it as well.”
The climate-eye connection
Despite being understudied, ophthalmologists know that the eyes can be affected by the environment. The ocular surface is directly exposed to environmental factors, making it highly susceptible to airborne pollutants like particulate matter.
“These pollutants can destabilize the tear film, cause inflammation, and exacerbate existing conditions such as dry eye and allergies, particularly in urban and industrialized regions,” explains study senior author Malik Kahook, MD, professor and Slater Family Endowed Chair in Ophthalmology.
The study specifically looked at concentrations of small PM in the range of 10 micrometers or less (PM10) and PM in the range of 2.5 micrometers or less (PM2.5) in diameter because of their known health effects.
“Pollutants like PM10 and PM2.5 are small enough to penetrate and adhere to the ocular surface, disrupting the tear film and triggering inflammation,” says Kahook, who acts at the vice chair of translational research in the Department of Ophthalmology. “Additionally, many contain toxic chemicals that activate oxidative stress pathways, further damaging the sensitive tissues of the eye.”
Researchers found that the clinic’s daily visit counts were 2.2 times higher than average when PM10concentrations were at 110 micrograms per cubic meter (µg/m³), which is within the Environmental Protection Agency’s established maximum containment levels for PM10.
Looking at both particulate matter sizes is important, the researcher say, because it reveals how health impact of different pollutants can vary.
“PM10 and PM2.5 differ in size and penetration ability. PM10, being larger, tends to irritate the ocular surface more directly, especially in colder temperatures according to our study findings,” Kahook says. “PM2.5, though smaller, can penetrate deeper into tissues and has a broader systemic inflammatory potential. Comparing these pollutants helps clarify their distinct roles in ocular health.”
Furthering research and clinic preparedness
As concentration level of particulate matter increased, so did the number of visits. Patnaik says this type of gradient effect can be difficult to establish with smaller datasets but gives important credibility to the findings because it shows that there’s likely a strong association between the two.
Patnaik says the researchers see value in studying the Denver metro region and would like to extend the research nationally or even globally, as pollution can differ greatly from one location to another. More data increases confidence in the link and can play an important foundational role in policies and regulation that directly benefits ocular and overall health.
The findings can also play an important role in the clinic, too. Monitoring pollution levels allows ophthalmologists to anticipate potential patient surges during high-pollution periods and adjust treatment recommendations. Air quality awareness may also allow clinicians to proactively counsel patients about enhancing use of treatments like artificial tears for dry eye and anti-allergy medications, as well as protective eye wear.
“This research underscores the need for ophthalmologists to consider environmental factors when diagnosing and managing ocular surface conditions,” Kahook says. “It provides evidence for integrating air quality awareness into clinical practice, which can improve patient education and treatment outcomes.”
