Furthermore, genetic factors are also known to be risk factors for glaucoma, in which single-nucleotide polymorphisms in numerous genes (e.g., myocilin, apolipoprotein E, X-ray repair cross-complementing group 1, zona pellucida glycoprotein 4) have been shown to be associated with an increased risk of glaucoma [9,10]. Here, ZP4 is linked to glaucoma.