Can the choice of artificial tears harm patients? A narrative review with an overview of the Nordic market.

Purpose: To provide an overview of artificial tears marketed in the following Nordic countries: Denmark, Finland, Norway, Iceland and Sweden. Furthermore, this review aimed to highlight the different preservatives and other constituents found in artificial tears in the Nordic market, focussing on adverse effects.

Methods: Artificial tears appearing in online pharmacies in Denmark, Norway, Sweden, Finland and Iceland were included, and tables listing their components were created. Based on the preservatives and other constituents found in the artificial tears on the Nordic market, a literature search was conducted to investigate differences and potential adverse effects. This was achieved using PubMed with MeSH and free text search terms. Included articles were (i) studies performed on humans in vivo or in vitro human models, (ii) published between 2000 and 2023 and (iii) focussing on adverse effects, preservatives, toxicity, other constituents and preservative-free artificial tears.

Results: A total of 88 artificial tears were found on the Nordic market. Approximately 32% (28 out of 88) of the artificial tears contain preservatives. Eleven of these are preserved with benzalkonium chloride (BAK) or cetrimide. After a thorough literature search, evidence has been found for the toxic effects of BAK and cetrimide. There is no evidence of toxic effects of lubricants, osmoprotectants and lipids.

Conclusions: The findings of this review highlight the paradoxical fact that many treatments for ocular surface diseases contain toxic preservatives that may lead to worsening of the condition. In particular, long-time toxic effects of BAK may contribute to disease progression.