TangNingTongluo tablet, a traditional Chinese medicine for the treatment of nonproliferative diabetic retinopathy: Study protocol for a randomized controlled trial

Background Diabetic retinopathy (DR) is a common microvascular complication of diabetes. At present, there are few safe and effective drugs for DR. We report the protocol for a pragmatic randomized controlled trial of the use of a traditional Chinese herbal medicine to treat patients with DR. Methods This will be a multicentre randomized controlled trial. A total of 240 participants diagnosed with nonproliferative diabetic retinopathy (NPDR) recruited from 11 institutions will be randomly allocated at a 1:1 ratio to two groups. The study is divided into a basic treatment period and an extended treatment period. All participants will receive a 24-week treatment and then be followed up for another 24 weeks. After the 24-week basic treatment period, the investigator will decide whether to enter the extended treatment period according to the patient's condition and willingness to continue using the drug until 48 weeks. The primary outcome is the mean change in best-corrected visual acuity and DR progression rate at weeks 24 and 48 compared to baseline. Discussion This study will provide evidence regarding the effectiveness and safety of TangNingTongluo tablets in treating patients with NPDR. Trial registration Chinese Clinical Trial Registry (http://www.chictr.org.cn), ChiCTR2100049803, registered on 9 August 2021.