Identification of microplastics in human tear fluid and meibum: Implications for dry eye disease pathogenesis

Microplastics (MPs) are emerging environmental pollutants that are increasingly being detected in various human tissues. However, their impact on ocular health is underexplored. This study investigated the presence of MPs in tear fluid and meibum of 45 patients with dry eye disease (DED). Various examinations were conducted, including the Schirmer I test, fluorescein tear film break-up time (FBUT) and other dry eye-related assessments. MPs were identified in the tear fluid and meibum and were categorized into five distinct types, with polyethylene (PE) being the most predominant. Notably, PE levels exhibited significant correlations with key DED parameters, such as Schirmer I test scores and FBUT. In in-vitro studies, PE exposure reduced the viability and induced apoptosis of human corneal epithelial cells and conjunctival epithelial cells in a dose-dependent manner. In mouse models, topical exposure to PE drops, which imitate airborne PE exposure, induced typical dry eye signs, reduced goblet cell numbers, and triggered conjunctival inflammation. PE-treated meibomian glands exhibited changes, but these changes were not statistically significant, possibly because of the limited duration of the study. This study is the first to confirm the presence of microplastics (MPs) in human tear fluid and meibum while also offering novel insights into the potential pathogenic effects of airborne MP exposure on ocular health.