Dr. Chang is considered an authority in the field of "Refractive Intraocular Lenses (IOLs)". To help educate patients about this topic, Dr. Chang wrote the scripts and collaborated with Eyemaginations to develop a series of patient educational videos. Called the “Chang IOL Modules”, these videos are marketed through Eyemaginations and are used by physicians around the Dr. Chang donates his royalties to the humanitarian cataract charities – Project Vision and Himalayan Cataract Project.

Within ophthalmology, Dr Chang is widely considered one of the leading cataract surgeons, educators, and clinical investigators in the world. In this capacity, he has often been selected by medical associations to respond to media requests for information.

Although curable with surgery, cataracts remain the leading cause of blindness in the world, accounting for more than one half of all blindness. Dr. Chang has used his international prominence to highlight and advance several important cataract efforts. He has traveled to many developing countries to perform and teach cataract surgery to local ophthalmologists.

The intraoperative floppy iris syndrome was first reported by Drs. David Chang and John Campbell in 2005. This major discovery showed that the most common prostate medications (such as Flomax) cause iris problems during cataract surgery that can lead to many complications if the surgeon does not anticipate them. Dr. Chang has done extensive clinical research and is considered one of the world authorities on how to avoid and manage these problems.