Short-Term Effects of Ground-Level Ozone in Patients With Dry Eye Disease: A Prospective Clinical Study

Purpose: To investigate changes in the clinical features of patients with dry eye disease (DED) according to short-term outdoor ground-level ozone exposure. Methods: This prospective observational study included patients with DED who were treated with the same topical drugs (0.05% cyclosporine or 3% diquafosol) and visited the hospital twice at 2month intervals. Patients who showed a short tear film breakup time and positive ocular surface staining were assigned to the diquafosol and cyclosporine groups, respectively. The ocular surface disease index (OSDI) score, tear secretion, tear film breakup time, and corneal fluorescein staining score were measured at each visit. The mean ground-level ozone concentration for 1 week before the ocular examinations was used as the ozone exposure level. Changes in dry eye parameters according to changes in ozone concentration were analyzed using univariate and multivariate linear analyses. Results: Thirty-three patients were included in the analysis. The mean age was 55.2 +/- 10.5 years. Ozone concentrations were significantly associated with increased OSDI scores (R = 0.304, P = 0.0006) and a decreased tear secretion (R = -0.355, P = 0.0012) in univariate models. In multivariate models, the results were consistent; the OSDI score increased by 3.43 points (beta = 3.43, P = 0.002), and tear secretion decreased by 1.43 mm (beta = -1.43, P = 0.015) per 0.01 ppm increase in ozone concentrations over a 2-month interval. Notably, the cyclosporine group showed more prominent changes in the OSDI score and tear secretion with changes in the ozone concentration (P < 0.05). Conclusions: Short-term exposure to increased ground-level ozone concentration led to increased ocular discomfort and decreased tear secretion in patients with DED.