Given that PTPN5 serves as a downstream component that adjusts the duration and functions of ERK signaling and that it is expressed specifically in rat RGCs (Paul et al., 2003; Li et al., 2016), we hypothesize that the relationship of PTPN5 with myopia may be related to the role of DA in refractive error. The gene discussed is MAPK1; the disease is myopia.