SMAD1 and myopia: The phosphorylation level of SMAD1/5 in the sclera of minus lens-wearing eyes was lower than that of non-wearing eyes, and it was not affected by the administration of 4-PBA (Supplemental Fig. 8d), indicating that the SMAD pathway is unlikely to be involved in myopia-induced abnormalities in scleral collagen gene expression and their correction by 4-PBA.