Which contact lens solution preservative is especially known to cause SLK?

• A. Thimerosal
• B. Benzalkonium chloride
• C. Chlorhexidine
• D. Sodium perborate

Answer: (A)

Preservatives in contact lens solutions can irritate the ocular surface, and SLK is classically linked to a preservative that causes surface toxicity with long-term lens wear. Benzalkonium chloride is a common preservative that acts as a detergent-like agent, disrupting the tear film, damaging conjunctival epithelial cells and goblet cells, and increasing friction at the superior bulbar conjunctiva under the eyelid. This combination promotes inflammation and changes in the superior limbic area compatible with SLK. Thimerosal can cause hypersensitivity reactions but is not the classic trigger for SLK, and chlorhexidine or sodium perborate are less specifically associated with this condition. Therefore, the preservative most associated with SLK is benzalkonium chloride.