Retinal leakage is not only a very common pathological phenomenon but also a common pathological feature of many retinal diseases, its pathogenesis is very complex. The application of ultra-wide-angle fluorescein angiography is one of the main means to observe and evaluate retinal leakage. Leakage index is a new index for evaluating retinal leakage. Studies have explored its correlation in diabetic retinopathy, retinal vein occlusion, uveitis and other diseases, evaluating treatment effects and predicting prognosis. However, the number of related studies is small and the conclusions are inconsistent. In the future, it is still necessary to further advance the quantitative analysis of leakage, the application of leakage in more diseases, and the clinical trials of leakage rate to explore its role in predicting and evaluating treatment effects in retinal diseases.