In a myopia animal model, Huibi et al. [82] discovered how reduced SOD, nitric oxide synthase (NOS) activity and nitric oxide (NO) content existed in the retinal pigmental epithelium choroid homogenate, and also how the administration of trace element zinc was able to not only increase these three parameters in myopic chick eyes, but also inhibit the elongation of axis oculi and increased dioptres. This evidence concerns the gene NOS2 and myopia.