A systematic evidence map of air pollution studies on various ocular diseases

Abstract

Eyes may be more susceptible to environmental chemicals, including air pollutants, than other organs because of the nature of their direct exposure to the external environment. Although the ocular effects of air pollution are increasingly recognized, studies that have systematically synthesized previous findings are limited. This study aimed to identify research gaps about the impact of air pollution on ocular diseases in epidemiological and animal experimental studies using a systematic evidence map (SEM). We formulated search terms to identify human and animal studies examining the effects of eight air pollutants on eleven ocular diseases (three diseases divisions: anterior segment, posterior segment, and refractive errors). We conducted searches in PubMed, Embase, and Ovid MEDLINE, limiting results to English-language articles published through April 30, 2025. We then created a SEM to visualize the volumes and characteristics of the available literature on this topic. From 3324 studies identified from three databases, 103 epidemiological studies and 22 toxicological studies were included in the SEM. Numbers of human and animal studies have gradually increased since 2014 and 2017, respectively. PM2.5 (88 studies) and NO2 (68 studies) were the most studied air pollutants, and anterior segment diseases (91 studies) were the most investigated among the three disease divisions. Most human studies were conducted in Asia using ambient monitoring data to measure air pollution. Most animal studies used mouse models with an eye drop-exposure method. PM2.5 and NO2 showed the strongest positive associations with ocular diseases, particularly with anterior segment diseases.