For exposures with competitive mediation effects, increased IL-18 levels (OR = 0.929, 95% CI: 0.889–0.971, p < 0.001) after adjusting for CD8dim T cell %T cell, increased CD62L− HLA DR++ monocyte AC levels (OR = 0.869, 95% CI: 0.769–0.961, p = 0.012) after adjusting for IL-12 subunit B levels, and increased CD62L− plasmacytoid dendritic cell AC levels (OR = 0.899, 95% CI: 0.819–0.981, p = 0.021) were significantly associated with a reduced risk of OM. The gene discussed is IL18; the disease is ocular melanoma.