Association of Serum Vitamin D, IgE, Eosinophils, and Time Spent Outdoor During Daylight with Disease Severity in Vernal Keratoconjunctivitis

This retrospective cross-sectional study examined differences in serum 25-hydroxyvitamin D (25-OH D), total IgE, eosinophil levels, and outdoor exposure time in relation to disease severity in children with Vernal Keratoconjunctivitis (VKC). It also assessed these parameters across VKC subtypes. The study included 40 VKC patients and 43 healthy controls. Ophthalmologic examinations, serum 25-OH D, total IgE, eosinophil levels, and outdoor exposure times were evaluated. Disease severity was graded using Bonini's system. Multinomial logistic regression was used for statistical analysis. VKC patients had significantly lower 25-OH D (16.70 ± 5.50 vs. 23.98 ± 7.83 ng/ml, p < 0.001), higher IgE (248.52 ± 161.16 vs. 34.86 ± 17.38 ng/ml, p < 0.001), elevated eosinophils (365.72 ± 182.43 vs. 152.06 ± 80.23 cells/ml, p < 0.001), and reduced outdoor time (136.50 ± 42.39 vs. 210.0 ± 44.40 minutes, p < 0.001) compared to controls. 25-OH D negatively correlated with IgE (r = -0.505, p < 0.001) and eosinophils (r = -0.643, p < 0.001). Elevated IgE was significantly linked to mild-to-moderate VKC severity (OR = 1.120, p = 0.001). VKC patients exhibited lower serum 25-OH D and reduced daytime outdoor exposure, likely due to photophobia, compared to controls. No significant association was found between vitamin D or outdoor time and VKC severity. High IgE and eosinophil levels support VKC's allergic origin. The inverse correlations between 25-OH D, IgE, and eosinophil may suggest an immunomodulatory role. Large-scale, prospective interventional studies are warranted to validate these findings and elucidate causal relationships.