It is well established that limited tear exchange in the scleral lens (SL) post-lens fluid reservoir (FR) decreases the clearance of inflammatory mediators, cellular debris, and metabolic byproducts.^1-5 Thus, these components accumulate and interact during SL wear since the FR may act as a sequestered microenvironment.

A recent cross-sectional study aimed to characterize the cellular and molecular composition of the SL fluid reservoir FR in individuals who have keratoconus and to verify whether the FR exhibits disease-specific inflammation.⁶ This study analyzed post-lens FR samples from habitual SL wearers who have keratoconus and from individuals with normal eyes who wore SLs using a standardized short-term SL protocol.

Samples were collected after a minimum of 2 hours of lens wear. In total, 31 individuals were included in the study, 21 in the keratoconus group and 16 in the normal group. Inclusion criteria included current SL wear in at least 1 eye, at least 2 hours of lens wear before evaluation, and lens application using a specified preservative-free saline solution. Exclusion criteria included failure to meet the minimum lens-wear duration or the use of an alternative lens-filling solution.

Leukocyte concentrations were determined using an automated hematology analyzer. A multiplex bead-based immunoassay was performed to quantify 19 cytokines, chemokines, and growth factors. Anterior segment optical coherence tomography was utilized to evaluate FR characteristics. Differences among groups were analyzed using the Kruskal–Wallis test, with Benjamini–Hochberg correction applied to control the false discovery rate. Correlations between outcome measures were evaluated using Spearman rank correlation analysis.

Immune cell counts in the fluid reservoir were significantly higher in eyes that have keratoconus than in normal eyes (P=.02). Eyes that have keratoconus exhibited a distinct proinflammatory cytokine profile, with significantly greater concentrations of eotaxin, IL-4, IL-15, MIP-1β, and TNF-α compared to normal eyes.

Conversely, the concentrations of IL-7 and IFN-γ were higher in normal eyes. Several additional inflammatory mediators (eg, IL-6, IL-8, MCP-1) trended higher in concentrations in eyes that had keratoconus but did not remain significant after correction for numerous comparisons. Eyes that had keratoconus exhibited a distinct proinflammatory cytokine profile and elevated leukocyte counts within the FR, supporting the model of localized inflammatory activity in keratoconus.

The FR beneath a scleral lens is a dynamic, biologically active microenvironment influenced by both underlying ocular surface disease and the physiologic effects of lens wear. Eyes that have keratoconus demonstrated a distinct proinflammatory cytokine profile within the FR, consistent with increased cellular infiltration and localized inflammatory signaling.

These findings suggest that the FR may sequester and concentrate disease-associated mediators, supporting its potential role as a novel in vivo sampling compartment and a possible target for therapeutic intervention during scleral lens wear.

Future longitudinal studies to evaluate changes within the FR and opportunities for its modulation may help guide strategies to optimize SL performance and improve clinical outcomes in keratoconus.

References

1. Tse V, Tan B, Kim YH, Zhou Y, Lin MC. Tear dynamics under scleral lenses. Cont Lens Anterior Eye. 2019;42(1):43-48. doi: 10.1016/j.clae.2018.11.016

2. Skidmore K, Walker M, Marsack J, Bergmanson J, Miller W. A measure of tear inflow in habitual scleral lens wearers with and without midday fogging. Cont Lens Anterior Eye. 2019;42(1):36-42. doi: 10.1016/j.clae.2018.10.009

3. Caroline P, André M. How much tear exchange occurs beneath scleral lenses. Contact Lens Spectrum. 2014;29:64. clspectrum.com/issues/2014/july/contact-lens-case-reports

4. Paugh JR, Chen E, Heinrich C, Miller H, Gates T, Nguyen AL, et al. Silicone hydrogel and rigid gas-permeable scleral lens tear exchange. Eye Contact Lens. 2018;44:1. https://doi.org/10.1097/ICL.0000000000000400

5. Ko L, Maurice D, Ruben M. Fluid exchange under scleral contact lenses in relation to wearing time. Br J Ophthalmol. 1970;54(7):486-489. doi: 10.1136/bjo.54.7.486

6. Keyzer M, Guerra E, Bhattacharyya P, Walker MK. Immune cells and cytokines in the scleral lens fluid reservoir in keratoconus. Cont Lens Anterior Eye. 2026 Jul 17;49(5):102701. doi: 10.1016/j.clae.2026.102701

Melissa Barnett, OD, FAAO, FSLS, practices at Baker Optometry. She is also an International Coaching Federation (ICF) associate certified coach. She has received remuneration from ABB, AbbVie, Alcon, Azura, Bausch + Lomb, BCLA, Bruder, Cloudbreak Pharma, Dompé, Epion, OCuSOFT, ScienceBased Health, STAPLE Program, Tarsus, Tenpoint Pharmaceuticals, and Théa Pharma.

 This content is sponsored by Contamac.