From June 18th to 20th, the "21st Chinese International Congress of Ophthalmology and Optometry " (COOC 2021) was held in Shanghai Convention and Exhibition Center of International Sourcing. COOC 2021 invited well-known ophthalmologists, scholars, and young practitioners to focus on the cutting-edge ophthalmology research and development at home and abroad in various forms such as special lectures, summit forums, surgical video exchanges and comments, and focus on the innovations and outstanding issues in today's ophthalmology clinical trials, fully reflecting the direction of development of clinical diagnosis and treatment in ophthalmology.