Circulating Claudin-5 and Systemic Inflammatory Indices in Wet and Dry Age-Related Macular Degeneration

Background and Objectives: Age-related macular degeneration (AMD) is a multifactorial retinal disease in which inflammation and blood-retinal barrier dysfunction may contribute to disease pathogenesis. Claudin-5 is a key tight-junction protein involved in endothelial barrier integrity. Hemogram-derived indices such as the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), and pan-immune-inflammation value (PIV) reflect systemic inflammatory status. This study aimed to evaluate circulating claudin-5 levels and systemic inflammatory indices in patients with wet and dry AMD and to investigate their associations with visual function. Materials and Methods: This prospective case–control study included 90 participants: 30 patients with wet AMD, 30 patients with dry AMD, and 30 healthy controls. All participants underwent detailed ophthalmologic examination, including best-corrected visual acuity (BCVA) assessment and optical coherence tomography. Serum claudin-5 levels were analyzed by enzyme-linked immunosorbent assay, and NLR, PLR, MLR, and PIV were calculated from complete blood count parameters. Group comparisons, correlation analyses, and age-adjusted analyses were performed using appropriate statistical methods. Results: Age differed significantly among the groups (p = 0.032), with the highest median age in the dry AMD group. BCVA (logMAR) also differed significantly (p < 0.001), and both AMD groups had worse visual acuity than controls. Median serum claudin-5 levels were 2.42 in controls, 3.28 in the wet AMD group, and 3.10 in the dry AMD group, with no significant between-group difference (p = 0.280). NLR, MLR, and PIV were also comparable among the groups (p = 0.310, p = 0.410, and p = 0.752, respectively). PLR differed among the groups (p = 0.019), and post hoc analysis showed higher PLR values in the dry AMD group than in the wet AMD group (p = 0.013). However, this difference was no longer statistically significant after adjustment for age (adjusted p = 0.098). Serum claudin-5 was not significantly correlated with age, BCVA, NLR, PLR, MLR, or PIV. Conclusions: Circulating claudin-5 did not differ significantly across AMD phenotypes and was not associated with age, visual function, or systemic inflammatory indices. Although PLR differed between wet and dry AMD before adjustment for age, the overall findings suggest that single-point peripheral serum measurements of claudin-5 may have limited utility in reflecting local retinal barrier-related changes in AMD. Larger longitudinal studies are needed to clarify its potential biomarker role.