https://www.selleckchem.com/products/ficz.html INPLASY2020100102. INPLASY2020100102. Anal fistula is characterized with perianal cellulitis, anorectal pain, smelly or bloody drainage of pus, and difficulty in controlling bowel movements. Ligation of intersphincteric fistula tract (LIFT) technique is a recently developed approach against anal fistula, and it could alleviate the pain of the patient, with little postoperative trauma, which can greatly shorten the wound healing time and hospitalization stay. We conduct the meta-analysis and systematic review to systematically evaluate the clinical efficacy and safety of LIFT in the treatment of anal fistula. Randomized controlled trials of LIFT against anal fistula will be searched in several Chinese and English databases. Two reviewers will independently conduct the literature extraction and risk of bias assessment. Statistical analysis will be conducted in RevMan 5.3. The study will help to systematically evaluate the clinical efficacy and safety of LIFT in the treatment of anal fistula. DOI 10.17605/OSF.IO/T4FUH. DOI 10.17605/OSF.IO/T4FUH. Diabetic retinopathy is a common complication of diabetes with a high incidence, and vitamin D deficiency is associated with diabetic retinopathy. Serum 25-hydroxy vitamin D [25-hydroxy-vitamind, 25 (OH) D], a product of vitamin D in the body, is considered the best indicator of a person's vitamin D nutritional status, and can be determined by measuring the concentration of 25 (OH) D. The purpose of this study is to systematically evaluate the correlation between serum 25-hydroxy vitamin D levels and diabetic retinopathy. To search English databases (PubMed, Excerpta Medical Database (Embase), Web of Science, the Cochrane Library) and Chinese databases (Chinese National Knowledge Internet, Development, and Evaluation (CNKI), WanFang, Viper, Chinese Biomedical Literature Database) by computer about Clinical study on the correlation between serum 25-hydroxyvitamin D level and diabeti