We hypothesized that reduced proliferation of scleral fibroblasts and decreased expression of α-SMA in myopic guinea pigs caused thinning of scleral tissues and weakening of tissue resistance, which in turn led to growth of the axial length, decreased tension of scleral tissues, down-regulation of fibroblast activity, and entry into a vicious circle, further accelerating the lengthening of the axial length, and promoting the development of myopia. This evidence concerns the gene ACTA1 and myopia.