Myopia is a global epidemic ametropia caused by a combination of genetic and environmental factors [
1]. Worldwide, the number of people with high myopia (HM) is approximately 163 million, accounting for 2.7% of the total population. It is estimated that by 2050, the number of people with HM will increase to 938 million, accounting for 9.8% of the total population. The number of people with HM in China is 87 million, accounting for 6.3% of the total population. It is estimated that by 2050, the number of people with HM will exceed 175 million, accounting for 13% of the total population [
2]. Surveys have shown that the prevalence of HM in Chinese adolescents is 6.69–38.4%; that is, China is a typical country with a high incidence of HM [
3,
4]. As myopic refractive errors increase, especially up to HM, the incidence of fundus lesions, risk of blindness and medical costs also increase [
5]. Pathological myopia (PM) was reported to be an important cause of global vision loss, and the prevalence of PM is 0.9 to 3.1%. The prevalence of PM associated with visual impairment in European countries is 0.1 to 0.5%, and the prevalence in Asian countries is high, ranging from 0.2 to 1.4%. Studies in China have shown that PM is the most common cause of blindness, accounting for 26.1% of cases [
6]. At present, the occurrence of myopia tends to be higher in younger people and is in a more advanced stage. HM fundus lesions, especially macular degeneration, are the main causes of blindness in East Asian countries [
7].
The form deprivation myopia (FDM) theory was proposed in 1977. After Wiesel et al. [
8] sutured the eyelids of newborn rhesus monkeys, the sutured eyes caused obvious axial myopia. According to research needs, some scholars have carried out myopia research on the eyes of animals such as tree shrews [
9,
10], chickens [
11], mice [
12], rats [
13], and guinea pigs [
14]. Studies have confirmed that form deprivation (FD) in young animals leads to abnormal growth of the eye axis and the formation of obvious myopia [
15,
16]. Guinea pigs are widely used in the current research on myopia since the eyeball structure and emmetropization mechanism are similar to those of human myopia. The mechanism of HM formation is very complicated, and local retinal regulation is a focus of research. It has been shown that in myopic eyes, the axial length increases, and vascular changes, such as retinal vascularization diminishing and narrowing, are observed [
17]. Shih’s research revealed that along with the increase in myopic refractive errors, the ocular pulse amplitude, which is generated by choroidal blood flow, was decreased. The circulatory disturbance was observed in the formation of myopia [
18]. Oxidative stress (OS) is not only involved in the development of myopia but is also accompanied by the complications of HM. The elevated level of malondialdehyde (MDA) in the vitreous of myopic subjects strongly suggests retinal lipid peroxidation involvement in the genesis of the human myopic cataracts [
19]. OS levels and metabolic activities in the aqueous humour were lower in patients with high myopia than the controls [
20]. Simonelli et al. [
21] demonstrated that lipid peroxidation might be associated with the pathogenesis of severe myopia. MDA, as the breakdown product of lipid peroxidation, would induce the accumulation of soluble proteins and fragmentation of the membrane structure. Bhatia et al. [
22] also stated that OS was related to myopic lens. Compared with that in age-related cataracts, the content of superoxide dismutase (SOD) was lower in myopic patients. Compared with that of healthy controls, the MDA level in plasma was higher in myopia. Shkrebets [
23] reported that the antioxidant capacity in tears is weakened in HM patients. To some extent, SOD, as the first line of defence against OS and an important component of the enzymatic antioxidant defence system in the retina, can increase the activity of endogenous peroxide detoxifying activity. Xu Huibi et al. [
24] reported that the SOD activity decreased in the retina of myopic eyes in form-sense-deprived chicks. However, fewer studies about the activities of total SOD in form deprivation high myopia (FDHM) in guinea pigs have been performed. This study intended to establish a guinea pig model of FDM to simulate HM, observe changes in the retinal and scleral morphology, determine the MDA content in the retina and sclera, and assess the SOD activity. The relationship between oxygen free radicals and the formation of FDHM provides new ideas and a basis for further research on myopia, especially HM.