PPIG and optic nerve disorder: Genes that are included in this category are genes that encode ATP-binding cassette (ABC transporter), solute carrier family (SLC transporter), metabolizer enzymes; cytochrome (CYP), UDP-glucuronosyltransferase (UGT), aldehyde dehydrogenase (ALDH), glutathione S-transferase (GST), vitamin D receptor (VDR), pregnane X receptor (PXR), and genes related to optic neuropathy (Takahashi et al., 2008; Ramachandran and Swaminathan, 2012; Fatiguso et al., 2016; Pontual et al., 2017; Sun et al., 2019; Peng et al., 2021) (Figure 3).