Effects of contact lens wear on tear inflammatory biomarkers

This review article intends to critically review the available literature relating to the behavior of tear-borne inflammatory biomarkers during contact lens wear.

The workflow protocol followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement recommendations. An exhaustive search was carried out using the PubMed database. The analysis included a list of 34 eligible clinical trials: Thirty addressed the use of soft contact lenses, three focused on rigid gas permeable lenses; and one on scleral lenses. The biomarkers' presence was described as changes in the molecular concentration compared to control groups - non-contact lens wearers - or baseline measurements.

Contact lens wear inflates the concentration of several inflammatory molecules in tears. Most relevant changes were found for IL-1β, IL-6, IL-8, IL-17, LTB₄, and MMP-9. The use of rigid gas permeable lenses seems to produce a more robust sub-clinical inflammatory response than soft contact lenses, with significant contributions of IL-8, MMP-9, and EGF. Reusable lenses that are worn continuously or on a daily modality are more likely to raise the expression of biomarkers compared to daily disposables.

Mechanical trauma, hypoxia, and wearing schedules may be associated with a distinct sub-clinical inflammatory response in contact lens wearers. The relationship between these responses and contact lens-induced discomfort remains unclear, as the existing scientific evidence is still scarce. More clinical studies are still needed to prove the impact of reverse geometry and scleral lens wear on the behavior of tear-borne biomarkers.