This is a study aiming to assess the efficacy and safety of Keluo Xin capsule in patients with moderately severe to severe nonproliferative diabetic retinopathy (NPDR). Two-thirds of participates will receive Keluo Xin capsules while other one third will receive placebo.

This study composes two parts. The first is a 24-week period during which subjects receive designed treatment regimen; after that, subjects will be informed again for the next 24-week regimen (extention phase) and can choose whether or not to participate in the treatment (with the same regimen in the first period) voluntarily.

Inclusion Criteria:

• 18 years to 70 years;
• Patients diagnosed with type 2 diabetes mellitus;
• Patients diagnosed with nonproliferative diabetic retinopathy;
• Patients diagnosed with traditional Chinese medicine syndrome(TCM) differentiation of both Qi and Yin deficiency with blood Stasis;
• HbA1c≤8.0%;

Exclusion Criteria:

• Study eye been received panretinal photocoagulation;
• Study eye with neovascular elsewhere or neovascular of the disc, or neovascularization of iris;
• Prior panretinal photocoagulation in the study eye within 6 months;
• Uncontrolled blood pressure;
• Subjects who develop chronic diarrhoea;
• Any history of acute diabetic complications;
• Any history of allergy to components of Keluo Xin capsule;
• Pregnant or breast-feeding women.