[Ocular surface and outdoor air pollution: A systematic review]

Air pollution has steadily increased for several decades, with widely studied effects on human health, including increased mortality, incidence of stroke, respiratory and allergic disease. However, the effects of pollution on the ocular surface, in direct contact with the outside world, have been less precisely studied.

We conducted a literature review of articles on the subject published from 1966 to October 2020. Among the 661 articles identified, 33 were retained. Ocular surface disease associated with pollution included non-specific conjunctivitis, dry eye disease, blepharitis, and allergic conjunctivitis. The studied pollutants were particulate matter less than 2.5μm and 10μm (PM2.5, PM10), ozone (O₃), nitrogen dioxide (NO₂), carbon monoxide (CO) and sulfur dioxide (SO₂). Certain air quality parameters such as temperature and relative humidity were also studied.

Among the markers of air pollution possibly associated with ophthalmic disease, NO₂ and SO₂ appear to be the most frequent and highly correlated. High temperatures and low humidity levels also appear to be aggravating factors for the ocular surface. However, due to the heterogeneity of the studies, the results must be interpreted with caution. Indeed, the methodology and the results of the various studies are sometimes contradictory. The inclusion of patients, the analysis of environmental data, and the correlation between these two elements indeed raise numerous methodological questions.

Air pollution control would appear essential, as well as the development of new studies based on reliable methods of studying the environmental and its clinical effects.