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

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.