Air Pollution Can Take a Toll on Eyes

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The development of autoimmune eye diseases is typically attributed to genetic factors. But now, a compre­hensive review of more than 30 studies by researchers from Anhui Medical University and Shanghai Jiao Tong Uni­versity, in China, shows a correlation between environmental factors and autoimmune eye diseases, including uveitis, Graves ophthalmopathy, ocular allergic disease, glaucoma, and diabet­ic retinopathy. Of greatest concern is exposure to particulate matter and to­bacco smoke, insufficient sun exposure, and high heat.¹

NEW YORK, NEW YORK. In June 2023, the Statue of Liberty appears shrouded in smoke from the Canadian wildfires.

Particulate matter. One key finding from the review is that “long-term ex­posure to fine and ultrafine particulate matter, such as PM2.5 and PM0.1, from air pollution can activate inflammato­ry cells and reduce blood flow in the retina, exacerbating autoimmune eye diseases,” said Tsai-Chu Yeh, MD, at Taipei Veterans General Hospital, who was not involved with the review but has published research on environmen­tal factors and eye health.

Excessive tobacco smoke. Dr. Yeh noted that in vitro studies of cells from Graves ophthalmopathy patients found increased fibroblast proliferation in the presence of tobacco smoke. She said, “Environmental tobacco smoke expo­sure promotes fibroblast activity and affects the extracellular matrix.”

Heat and sunlight. The review also found that a lack of vitamin D in the eye due to insufficient sun exposure may contribute t autoimmune eye disease, said Dr. Yeh. In one of the studies reviewed, “the finding that the eye may have the ability to synthesize and utilize vitamin D3 locally when exposed to ultraviolet B radiation from sunlight is interesting,” she said. “This discovery challenges the traditional belief that the primary source of vitamin D is through dietary supplementation or synthesis in the skin.”

Dr. Yeh added that the study “highlights the therapeutic potential of an active form of vitamin D in attenuating the progression of autoimmune eye diseases by suppressing Th17 responses and inhibiting IL-17 production.”

Heat. Th17 cells come into play with exposure to high temperatures, as well. The authors wrote that heat stress contributes to the promotion of Th17 cells and activation of neutrophils, which can aggravate autoimmune eye disease.

Clinical take-home. People who are most at risk have preexisting autoimmune eye diseases and reside in areas with high pollution levels or are exposed to indoor air pollutants, including environmental tobacco smoke, said Dr. Yeh. She suggested that clinicians educate patients about the potential impact of air pollution and meteorological factors on their eye health and emphasized “avoiding outdoor exposure during times of high pollution or extreme weather conditions.”

Dr. Yeh hopes the study findings encourage eye specialists to collaborate with each other, other health care professionals, and public health authorities to advocate for improved air quality regulations and awareness campaigns.

—Patricia Weiser, PharmD

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1 Cao F et al. Environ Res. 2023;231(Pt 1):116116.

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Relevant financial disclosures: Dr. Yeh—None.

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