Heavy Metal Deposition and Parameter Change of Soft Contact Lenses by Exposure to Particulate Matter

Background: Particulate matter (PM) is known to contain heavy metals and harmful to the human body including the eyes. As such, in this study, the deposition of heavy metals from PM on soft contact lenses was examined, and changes in the lens parameters were further investigated. Methods: Six types of soft contact lenses were exposed to captured PM for eight hours. The central thickness, water content, refractive power, and oxygen transmissibility of each contact lens were measured after analyzation of the amounts of six heavy metals adsorbed on the contact lenses. Results: Lead, manganese, barium, arsenic, vanadium, and cadmium were detected in the captured PM, and only lead was adsorbed on all soft contact lenses except senofilcon C. The largest absorption was 5.50% of the lead on lotrafilcon B. The oxygen transmissibility of nelfilcon A exhibited statistically significant changes, however, it was within the ISO standard tolerance. Nevertheless, changes in the central thickness, water content, and refractive power of each soft contact lens were not statistically significant. Conclusions: This study revealed that a considerable amount of lead in PM was adsorbed on soft contact lenses, resulting in statistically significant changes of oxygen transmissibility. Thus, wearing soft contact lenses under high PM concentration might affect the physiology of the eyes.