ATF4 and cataract: To verify the activation of the PERK/eIF2α/ATF4 pathway in the lens of the three cataract groups, the protein levels of phosphorylated eIF2α (p-eIF2α) (Fig 3A and 3B) and the gene expression of ATF4 (Fig 3C) were detected by Western blot analysis and a quantitative real-time PCR assay, respectively.