For instance, some significant biomarkers include (i) Tau, amyloid-β-42, and lysozyme-C associated with Alzheimer’s disease; (ii) peroxiredoxin-6 and α-synuclein linked to Parkinson’s disease; (iii) lactotransferrin and lipophilin-A relevant to diabetic retinopathy; (iv) zinc-alpha-2 glycoprotein-1, prolactin, and calcium-binding protein-A4 pertaining to Graves’ orbitopathy; and (v) interleukin-6, interleukin-1β, TNF-α, and MMP-9 involved in dry eye disease [40,44,90,91,92]. The gene discussed is MMP9; the disease is Parkinson disease.