Dr Billy Tan graduated from the National University of Singapore in 1981 and was admitted as Fellow to the Royal College of Physician & Surgeons (Glasgow) in Ophthalmology in 1987, Fellow to the Royal College of Ophthalmologists in 1989 and Fellow to the Academy of Medicine in 1992.

He was awarded the Ministry of Health HMDP Scholarship in 1990 to train under Dr James Cairns at the Royal Victorian Eye and Ear Institute, Melbourne, in diseases and surgery of the vitreous and retina. Upon his return, he worked at the Singapore National Eye Centre as Consultant Ophthalmologist from 1993 to 1995, when he started private practice at Gleneagles Medical Centre.

Dr Tan was appointed as a visiting consultant to Tan Tock Seng Hospital since 1995. His practice there has been confined mainly to vitreo-retinal surgery. He was also appointed as a visiting consultant to Toa Payoh Hospital in 1995 until the hospital's closure in 1997, whereupon he was appointed visiting consultant to Changi General Hospital until 2003, again specializing in vitreo-retinal surgery. Dr Tan was appointed as Head, Surgical Retina Service of The Eye Institute, National Healthcare Group since May 2001.