Serum Vitamin D Levels in Patients with Vernal Keratoconjunctivitis: A Systematic Review and Meta-Analysis.

Purpose: To conduct a systematic review and meta-analysis to provide an outline of available data on the association between serum vitamin D levels and vernal keratoconjunctivitis (VKC) and to determine the possible relationship in children.

Methods: Systematic research on all articles published until July 2023 was conducted in PubMed, SCOPUS, Web of Science, and Embase. All observational-analytical studies that measured vitamin D levels in patients with VKC were included. Extracted data were included in two separate meta-analyses: 1) a meta-analysis on the standardized mean difference (SMD) of vitamin D levels between VKC patients and the control group and 2) a meta-analysis on the prevalence of vitamin D deficiency in VKC patients.

Results: Seven relevant studies that included 316 patients, with the mean age of 10.8 3 ± 1.14 years, with VKC were included in this meta-analysis. The mean serum vitamin D level was significantly lower in the patients with VKC as compared with the control group (SMD: -0.92; 95% CI -1.15, -0.69, p < 0.001). The overall prevalence of vitamin D deficiency among VKC patients was 63.7% (95% CI 42.5%-80.7%, p < 0.001). VKC patients spent significantly less time outdoors during daylight compared to healthy individuals (SMD = -0.90, 95%CI -1.28, -0.52, p < 0.001).

Conclusion: VKC patients have lower serum vitamin D than healthy controls. This finding underscores the potential role of vitamin D in the immunopathogenesis of VKC.