3.1 Characteristics of eligible studies
The literature search flow chart is shown in Figure 1. After screening 1138 articles and registered clinical trials, a total of 16 studies between 2005 and 2022 were included in the meta-analysis according to predetermined criteria, involving 834 eyes (575 patients).22-37 The main characteristics of the selected studies are collated in Table 1. Among the 16 RCTs, 1 studie was registered and 15 studies were published in English. The diseases involved were diabetic macular edema (11 RCTs), diffuse diabetic macular edema (DDME) (2 RCTs), refractory diabetic macular edema (RDME) (1 RCT), and macular edema associated with branch retinal vein occlusion (BRVO-ME) (2 RCTs). Of the included studies, 13 were two-arm studies and 3 were three-arm studies. Subsequently, we divided interventions into a placebo group and the following 4 groups: IVTA, RITA, SCTA, and STiTA. Fourteen RCTs involved IVTA compared with other routes of TA administration (the retrieved routes of administration contained RITA, SCTA, and STiTA); 6 RCTs compared TA to placebo (the retrieved routes of TA administration contained IVTA, STiTA and RITA); and 3 RCTs both the intervention group and the control group received intravitreal bevacizumab, which was a full-length humanized monoclonal antibody against vascular permeability-associated endothelial growth factor. The baseline characteristics included the overall proportion of men, 52.01%; age, ranging from 39.5 to 76.67 years; and length of follow-up, from 12 to 24 weeks. In addition, none of the trials were funded by pharmaceutical companies.