RVO has become the second most common blinding retinal vascular disease, and the incidence rate in Asian countries is about 0.57%[8]. Relevant studies show that RVO is mostly related to hypertension, hyperlipidemia and retinal arteriosclerosis[11]. It may be related to the greatly increased proportion of spicy and greasy food in people's diet, especially in some ethnic minority inhabited areas, which have characteristic food culture, such as Miao people like acid and wine, and Dong people like waxy food and good pickling[12].
ME is the most common complication of BRVO[13]. It can be caused by insufficient arterial blood supply, damaged venous wall, abnormal hemodynamics, some inflammatory factors, damaged blood retinal barrier and increased vascular permeability. It is difficult for the posterior venule to transfer liquid to the anterior vein through the capillary network, resulting in reflux obstruction. The blood pressure at the common vein trunk of the optic disc is large, which is difficult to pump back, so it is directly stored in the retinal space[14]. BRVO-ME is the most important cause of central vision loss in patients[15]. The clinical manifestations of patients often include visual acuity reduction and visual object deformation, which can be clearly diagnosed according to optical coherence tomography(OCT)[16], fundus photography[17], Fluorescein fundus angiography(FFA)[18], etc. At present, the treatment methods for BRVO-ME mainly include retinal laser photocoagulation and intravitreal injection (anti VEGF drugs and glucocorticoids)[19]. Intravitreal injection of anti VEGF drugs has become the main therapy of BRVO-ME including Ranibizumab[20], Conbercept[7, 21–23] and Aflibercept [4, 24–26]. Conbercept is a recombinant fusion protein of VEGF receptor and human immunoglobulin FC segment gene[21]. The drug competitively inhibits the binding of VEGF and receptor and prevents the activation of VEGF family receptors by binding vascular endothelial growth factor VEGF, so as to inhibits endothelial cell proliferation and angiogenesis[22]. At present, clinical trials have proved that intravitreal injection of anti VEGF drugs is effective in the treatment of BRVO-ME[27], which can reduce macular edema and improve the best corrected visual acuity of affected eyes. Glucocorticoid can reduce the expression of inflammatory factors and VEGF, but intravitreal injection of glucocorticoid may increase the incidence of high intraocular pressure and cataract[28]. However, there are no reports on clinical studies among different nationalities in the same region, so this study makes up for the clinical basis of anti VEGF drugs in the treatment of BRVO-ME to a certain extent.
In this study, the BCVA of the three groups at 1, 3, 6 and 12 months after treatment was significantly higher than that before treatment (P < 0.05), but there was no significant difference between different nationalities (P > 0.05). The CMT of the three groups decreased significantly after 1, 3, 6 and 12 months of treatment (P < 0.05), but there was no significant difference in the degree of CMT reduction among patients of different nationalities. Remission of me usually leads to the improvement of BCVA. However, some patients have limited improvement of BCVA after remission of ME. BRVO combined with me can cause changes in the fine structure of macular retina. In this study, it was observed that the integrity of ellipsoid zone and external membrane were related to the good visual prognosis of BRVO-ME patients, which was consistent with the results reported in some studies[29]. The state of no perfusion in the macular region is related to vision, and the state of photoreceptors is also involved in the process of vision damage. The damage of retinal blood barrier caused by BRVO-ME will cause irreversible damage to photoreceptors. Photoreceptor cells transmit visual information to the synapses of ganglion cells, and capillaries provide nutritional support. When capillary hypoperfusion occurs, insufficient nutrition of synaptic connection can lead to visual impairment. This suggests that we should pay attention to these subtle structural changes in the process of diagnosis and treatment, so as to predict the recovery degree of BCVA.
Our institute is located in Kaili City, Guizhou, Southwest China. According to the data of the sixth census of Guizhou Province[30], the total population of Qiandongnan Prefecture is 4.6344 million. The population of minority nationalities accounts for 79.7% of the total population, including Miao 42.09% and Dong 31.86%, which are the most densely populated area of Miao and Dong nationalities in China, and the most populous Autonomous Prefecture among ethnic minority autonomous prefectures in China. The surrounding counties close to Kaili City, such as Leishan, Huangping and Taijiang, are mainly inhabited by the Miao nationality, while the Dong nationality is mainly inhabited in Rongjiang, Congjiang and Liping counties far away from Kaili city. The ophthalmology department of our hospital is one of the top specialties in the General Hospital of Qiandongnan Prefecture in terms of annual outpatient volume, number of inpatients and number of operations. The sub specialties are relatively complete, and the analysis of relevant data on the epidemiological distribution of patients is representative[31]. Since the work of intravitreal injection of anti VEGF drugs was carried out in 2012, we found that Among BRVO patients, Han nationality has the highest treatment rate, followed by Miao nationality, Dong nationality, and some minority nationalities such as Ge family, Yao nationality and Gelao nationality. The rate of BRVO Dong patients in our hospital is relatively low because of low incidence rate, regional factors or other reasons, which we will further pay attention to and study.