Lipid Layer Thickness in Soft Contact Lens Wearers With and Without Lenses In Situ—A Systematic Review and Meta-Analysis

Objectives: To systematically review and quantitatively synthesize lipid layer thickness (LLT) measurements in soft contact lens (CL) wearers obtained in the presence and absence of contact lenses in situ. Methods: A systematic literature search of PubMed, Scopus, and Web of Science databases was conducted in accordance with PRISMA guidelines. Six studies meeting predefined inclusion criteria were included. Pooled mean LLT values were calculated using fixed-effects models, with heterogeneity, sensitivity analyses, and publication bias assessed. Results: In the absence of contact lenses, pooled LLT data from 86 healthy CL wearers yielded a mean LLT of 62.11 nm (95% CI: 47.33–76.90 nm). In the presence of contact lenses, pooled data from 330 subjects demonstrated a mean LLT of 69.52 nm (95% CI: 56.33–82.70 nm). Although LLT values were numerically higher with contact lens wear, the substantial overlap of confidence intervals indicated no consistent or statistically demonstrable difference between conditions. Conclusions: This meta-analysis provides the first quantitative synthesis of LLT in CL wearers and highlights the need for standardized methodologies to clarify the clinical relevance of LLT in contact lens-related tear film assessment.