Wildfire Smoke Induces Eye Surface Inflammation and Tear Film Changes in a Human Experimental Model

Abstract

Purpose: To investigate the short-term impact of exposure to smoke from vegetation burns on ocular surface symptoms and signs. Methods: Woody bushfuels were burnt in an enclosed room (Flammability Laboratory, University of Tasmania, Australia) to generate particulate matter and monitored in real time (Dust Trak II). Eighteen participants (aged 20–63 years, 8 males and 10 females) fitted with respirators were seated 1.5 m from the burn for 15 minutes. Clinical ocular surface measurements were conducted in the right eye. Tears were collected from the left eye and analyzed for the cytokine interleukin-1β (enzyme-linked immunosorbent assay). Pre-and postexposure differences were analyzed using paired t tests or Wilcoxon signed rank tests. Associations between symptoms and signs were analyzed using Spearman’s correlation. Results: Mean particulate matter with a diameter of 2.5 μm or smaller exposure was 1903 μg/m3. After smoke exposure, an increase in symptoms (median change, 2; interquartile range [IQR], 1–6; P = 0.001), ocular surface staining (median change, 1; IQR, 0–1; P = 0.007), limbal redness (mean change, 0.28 ± 0.36; P = 0.02), palpebral conjunctival redness (mean change, 0.35 ± 0.36; P = 0.009), palpebral conjunctival roughness (mean change, 0.3 ± 0.4; P = 0.046), and decrease in tear breakup time (mean change. 1.4 ± 2.6 seconds; P = 0.03) occurred. The change in bulbar conjunctival redness correlated with the change in dryness symptoms (r = 0.70; P = 0.001). The interleukin-1β concentration increased in the majority of participants post exposure (median change, 6.6 pg/mL; IQR, 2.2–21.1 pg/mL; P = 0.01). Conclusions: This study demonstrated that short-term wildfire smoke directly and adversely affects the ocular surface and induces symptoms. Translational Relevance: This study used a unique enclosed experimental laboratory to simulate ocular exposure to wildfire smoke and demonstrates the need to elucidate the role of anti-inflammatory therapies in mitigating the impact of smoke on the ocular surface.