Immune cells and cytokines in the scleral lens fluid reservoir in keratoconus.

PURPOSE: To characterize the cellular and molecular composition of the scleral lens (SL) fluid reservoir (FR) in keratoconus and determine whether this compartment reflects disease-specific inflammation.

METHODS

This cross-sectional study analyzed post-lens FR samples from habitual SL wearers with keratoconus and from normal eyes undergoing standardized short-term SL wear. Samples were collected after ≥2 h of lens wear. Leukocytes were quantified using an automated hematology analyzer, and 19 cytokines, chemokines, and growth factors were measured using multiplex bead-based immunoassays. Anterior segment optical coherence tomography (AS-OCT) was used to assess FR characteristics. Group differences were evaluated using Kruskal-Wallis testing with Benjamini-Hochberg false discovery rate (FDR) correction; correlations between outcomes were assessed using the Spearman rank test.

RESULTS

Thirty-seven participants were included, 21 in the keratoconus group and 16 in the normal group. All immune cell counts within the FR were greater in keratoconus compared to normal (p = 0.02), and keratoconus eyes demonstrated a distinct pro-inflammatory cytokine profile with significantly elevated eotaxin, IL-4, IL-15, MIP-1β, and TNF-α compared to normal eyes. Conversely, IL-7 and IFN-γ were higher in normal eyes. Several additional mediators (e.g., IL-6, IL-8, MCP-1) trended higher in keratoconus but did not remain significant after FDR correction.

CONCLUSIONS

The FR beneath a SL represents a biologically active and disease-sensitive microenvironment. Keratoconus eyes exhibited a distinct pro-inflammatory cytokine signature within the FR, suggesting increased cellular infiltration and localized inflammatory signaling. These findings support the concept that the FR can sequester and concentrate disease-related mediators, highlighting its potential as a novel in vivo sampling compartment and a target for therapeutic modulation in SL wear.