Dr John Chang was trained in Ophthalmology at Jules Stein Eye Institute UCLA, he then went to UCSF and did a fellowship there. He is the President of International Society of Refractive Surgery (ISRS) in 2018. Dr Chang is a Past President of the Hong Kong Association of Private Eye Surgeons. He is Honorary Associate Professor of The University of Hong Kong and the Chinese University of Hong Kong. Dr Chang is presently the Director of the Guy Hugh Chan Refractive Surgery Centre of Hong Kong Sanatorium & Hospital and has been interested in Cataract and Refractive Surgery for many years.  He is Clinical instructor for many refractive implants and surgeries including Lasik, Intra Corneal ring, Conductive Keratoplasty, Phakic Intraocular Lens and Phacoemulsification.  He is on the Executive Committee of the Asia Pacific Association of Cataract and Refractive Surgeons (APACRS) and the American Academy of Ophthalmology (AAO). He is on the Editorial Board of Cataract & Refractive Surgery Today, EyeWorld (Asia Edition) and Ocular Surgery News (APAO Edition), and is the chief editor of EuroTimes (China Edition).   He has also been awarded the "Certified Educator Award" by the APACRS, "Gold Medal" by IIRSI- India, "Distinguished Service Award" and Achievement Award" by the APAO, "Casebeer Award" by the International Society of Refractive Society (ISRS) and "Achievement Award" by the AAO.  Dr. Chang is also active in research, publishing and travelling abroad to give lectures as invited speaker in order to share his knowledge and findings.