Substance P Level in Tears as a Potential Biomarker for Contact Lens Discomfort.

Purpose: To analyze the effects of contact lens (CL) wear, time of the day, and CL discomfort (CLD) on clinical signs, tear inflammatory mediators and substance P.

Methods

Thirty symptomatic and 30 asymptomatic CL wearers attended two visits (morning and afternoon) on two days (non-CL and CL wearing days). Comfort, meniscus area, noninvasive breakup time (NIBUT), tear collection, hyperemia, lid parallel conjunctival folds, fluorescein staining, and sensitivity were performed. The tear levels of 23 inflammatory mediators and substance P were measured.

Results

Comfort, meniscus area, NIBUT, and MMP-9 were lower while conjunctival staining and EGF higher (p ≤ 0.015) on the CL wearing day. Comfort, IL-8/CXCL8, and VEGF were lower while EGF, IP-10/CXCL10, and MCP-1/CCL2 higher (p ≤ 0.047) in the afternoon. Comfort was lower and substance P higher (p ≤ 0.006) in symptomatic wearers.

Conclusion

Substance P may be implicated in CLD etiology; its role and potential application as a biomarker should be further studied.