Alterations in the Crystallization Pattern of Tear Fluid Induced by Increases in the Body Mass Index

(1) Purpose: The study investigated the correlation between variations in body mass index (BMI) and tear crystallization class according to the Masmali classification. Moreover, it examined the potential diagnostic value of a patterning test within the population affected by obesity. (2) Methods: A total of 61 patients were investigated, with ages ranging from 25 to 72 years (median age [interquartile range] = 39.0 [26] years). BMI values ranged from 19.1 to 47.5 kg/m², with a median BMI (interquartile range) of 29.3 (12.1) kg/m². (3) Results: The Kruskal-Wallis test was used to assess differences in BMI across the Masmali classes and revealed statistically significant disparities between at least two groups (p = 0.024). The rank η² value of 0.094 shows a small-to-moderate effect size, suggesting that approximately 9% of the variance in rank distributions is explained by the Masmali classification. The post hoc Dunn test with Bonferroni and Holm corrections showed that patients classified as Masmali grade 2 exhibited a significantly higher BMI compared to those in grade 0 (p = 0.009), whereas no statistically significant differences were identified between grades 0 and 1 or between grades 1 and 2. The analysis of variance (ANOVA) revealed a statistically significant difference among Masmali Classes 0, 1, and 2 with respect to the number of branching structures in dried tear samples analyzed at a brightness threshold of 220. The effect size (η² = 0.263) shows that approximately 26% of the variability in branching number can be attributed to the severity of tear film dysfunction as defined by the Masmali classification. Accordingly, as the Masmali score increases, the number of branches decreases significantly, particularly among patients with elevated BMI. (4) Conclusion: The findings suggest that when classified according to the Masmali scale the dry eye syndrome exhibits a distinct crystallization pattern in patients with excess body weight. Specifically, higher BMI values are associated with a marked decrease in the number of fern-like branches identified in the tear ferning test.