Systemic Inflammatory Markers in Patients with Metabolic Syndrome with and Without Dry Eye Disease: An Observational...

Background/Objectives: Metabolic syndrome (MetS) and dry eye disease (DED) share inflammatory mechanisms, yet few studies have examined objective tear function and serum inflammatory markers together in this population. The aim of this study was to compare tear function tests and a panel of systemic inflammatory indices between patients with MetS who did and did not have DED. Methods: This observational comparative study enrolled 104 adults with MetS (52 MetS-DED and 52 MetS-nonDED), with group-level comparability for age and sex. All participants underwent ophthalmologic evaluation, including the Ocular Surface Disease Index (OSDI), the Schirmer I test, and fluorescein tear break-up time (TBUT). DED was defined by a mean Schirmer I value of ≤5 mm/5 min. Routine blood tests were used to derive the neutrophil-, platelet-, monocyte-, and eosinophil-to-lymphocyte ratios (NLR, PLR, MLR, ELR), the neutrophil-lymphocyte-platelet ratio (NLPR), the C-reactive protein (CRP)-to-albumin ratio, and the monocyte-to-high density lipoprotein cholesterol (HDL) ratio. Between-group comparisons, receiver operating characteristic (ROC) analysis with Youden's index, and age- and sex-adjusted binary logistic regression were performed. Results: TBUT and Schirmer I values were significantly lower in the MetS-DED group, whereas OSDI scores did not differ between the groups. NLR, MLR, NLPR, CRP, and the CRP-to-albumin ratio were significantly higher in MetS-DED patients (all p < 0.05), while classic metabolic parameters were comparable. ROC analysis revealed statistically significant but weak-to-modest discriminatory ability (areas under the curve (AUCs) 0.617-0.652). In age- and sex-adjusted models, MLR (odds ratio (OR) = 1.072 per 0.01 unit, p = 0.046), the CRP-to-albumin ratio (OR = 1.062 per 0.01 unit, p = 0.011), and NLPR (OR = 1.123 per 0.001 unit, p = 0.038) remained significantly associated with MetS-DED. Conclusions: Among individuals with MetS, the presence of DED was accompanied by impaired tear function and a more pronounced systemic inflammatory profile despite similar metabolic parameters. However, the modest discriminatory performance and borderline adjusted associations indicate that these findings should be regarded as preliminary signals rather than evidence supporting the clinical use of these markers for screening or risk identification.