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Visual Acuity and Fundus The visual acuity of high myopia patients is significantly declined as the age advanced(Table 4). The number of fundus with lanquer cracks, submacular hemorrhages, Fuchs spot, choroidal atrophy of high myopic patient rose while age advanced (Table 5).
DISCUSSION
Myopia, affecting an average of about 30% (3%84%) of people throughout the world, is a leading cause of visual impairment [1].The degree of myopia in diopters (D) is classifed as follows: low (0.75 to 2.99D), moderate (3.00 to 5.99D), or high (<6.00D)[4]. Patients with pathologic myopia often resulting in irreversible central vision loss, developed an important cause of vision loss among working people[5]. So its necessary to study the profile of patients with high myopia including their age, sex, course, BCVA, refractive error and fundus to explore the correlation of each other and the evidence of prevention of development and progress of high myopia. In this study, among the 167 high myopia patients, there are 46 male patients and 121 female patients, we learned that the female patients are significantly higher than male patients (χ2=13.9,P=0.003)，the result is the same as the study of Vitale et al[6], He et al [7] and Xu et al [8]. It means that female may at higher risk than male. Estrogen may promote CNV development by increasing vascular endothelial growth factor receptor 2 (VEGFR2) gene expression via ERβ.We also observed that 17βestradiol(E2) played an important role in the regulation and modulation of VEGF, VEGFR2 mRNA, and subsequent endothelial cell proliferation [9]. This led us to question a possible role of E2 in ocular angiogenesis. The status of age and course of high myopic patients in this study, the age and course of different groups have significant difference. The SE of both eyes in group 2, 3 and 4 has no statistical difference between them, but the SE of the three groups are significantly increased than that of group 1. If age is named as independent variable, course and SE named as dependent variable, then make regression analysis on them and we can acquire regression equation: Course=0.641×Age8.654.From this equation we learned that SE and age has no correlation, while course and age has correlation, which indicated that age of incidence high myopia is mostly younger. So we should pay attention to prevent the incidence and progress of adolescent myopia.
Compare the visual acuity of high myopia in different groups, we learned that the age of high myopic patients is increasing while the rate of visual acuity ≥0.8 is declining from 50% in group1 to 2.0% in group 4. The rate of visual acuity <0.1 is increasing from 10% in group 1 to 54.0% in group 4(χ2=67.168，P=0.000), which may suggested that incidence of vision decrease is accompanied with ageing. Ageing is an important factor in the development of vision decrease of high myopic patients and affects retinal pigment epithelium dysfunction[10]. The lacquer cracks, subretinal haemorrhages，Fuchs spot and Choroidal atrophy are the major factors to affect vision of high myopic patients. Lacquer cracks, which are yellowish linear lesions found in the posterior of high myopic eyes, are an earlier sign of myopic maculopathy. lacquer cracks are suggested not to influence VA, except when they cross the fovea[10]. Lacquer cracks are formed by ruptures in Bruchs membrane, in which choroidal neovascularization (CNV) may develop[11]. CNV occurring in 5%～10% of individuals with high myopia and high myopia is the cause of 62% of CNV in patients less than 50 years of age[3],which is the important reason of vision loss of young patients and high myopia, generally leads irreversible central vision loss[12] in CNV eyes, indicates that the functional impairment is present not only in the outer macular layers (preganglionic elements) but also in the innermost macular layers (ganglion cells and their fibers).These new vessels leak blood and fluid and cause a buildup of fibroblasts and neovascular endothelial cells between and within the RPE and photoreceptor layers causing. In the early stage, a detachment of the RPE and retina. A persistent fibrovascular scar subsequently forms with a progressive loss of photoreceptors[11]. Pathologic myopia is associated with progressive stretching and thinning of the posterior pole and choroid with loss of choriocapillaries. The elongation of the globe causes vascular alterations, breaks in Bruchs membrane (lacquer cracks) with increased risk of CNV, besides progression of myopic macular chorioretinal atrophy[13].
In our study, some high myopic patients with spontaneous subretinal haemorrhages, which may developed by lacquer cracks formed by ruptures in Bruchs membrane , CNV, small fibrovascular tissue ingrowths which may cause elevated pigmented circular lesions (Fuchs spots) [14], around which sometimes combined with haemorrhages. All predispose high myopes can lead to rapid visual loss. In this study, we found that aged high myopic patients with declined vision acuity and worse retina was usually worse than that of young patients. So its necessary to follow up young high myopic patients to prevent the development of pathologic myopia and macular degeneration.
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