There are various diagnostics criteria to evaluate DED such as conjunctival staining, Schirmer test, blurred vision, filamentary keratitis, tear hyperosmolarity, impression cytology, blepharospasm, meibomian gland disease or eyelid inflammation, TBUT, corneal sensitivity, and inflammatory markers (HLA-DR, MMP9, cytokines etc.)[11]. The gene discussed is MMP9; the disease is blepharitis.