Dr Koh is Founding Partner and Senior Consultant at the Eye & Retina Surgeons, Camden Medical Centre; Director, Retinal Centre International, and Vice-President of the International Retinal Foundation. He is Visiting Consultant to the Vitreoretinal Service, Singapore National Eye Centre (SNEC) and Visiting Consultant to the Eye Institute, Tan Tock Seng Hospital; He is Council Member of the College of Ophthalmologists, Academy of Medicine, Singapore. He is the immediate Past President of the Singapore Society of Ophthalmology. He was Congress Vice-President & Secretary-General of the 21st Congress of the Asia-Pacific Academy of Ophthalmology (APAO) held in Singapore. He is the founding Chairman and Honorary Adviser to the Retinitis Pigmentosa Society of Singapore. He is also member of Retina International and the Asia-Pacific Advisory Board for Photodynamic Therapy, Lucentis and Medical Retina.

His past appointments include Deputy Head, Retina Research Group, SERI; Director, SNEC-SERI Visual Electrophysiology Laboratory; Director for the Undergraduate Curriculum in Ophthalmology, National University of Singapore (NUS); Visiting Consultant, National University Hospital (NUH); Treasurer-General of WORLDEYES; Head, Medical Photography Department, SNEC; Adjunct Scientist, Singapore Eye Research Institute (SERI);

Dr Koh completed Fellowships in Medical Retina at Moorfields Eye Hospital & Institute of Ophthalmology, London, UK (1998 – 1999) and at the Jules Stein Eye Institute, UCLA, Los Angeles, and USA (1999 -2000). He trained under Medical Retina specialists, Professors Alan C Bird, Susan Lightman and Graham Holder from Moorfields Eye Institute of London, and Professors Bradley Straatsma, John Heckenlively, Steven Schwartz, Kent Small and Marc Yoshizumi of the Jules Stein Eye Institute, UCLA. The recipient of numerous awards, Dr Koh has authored or edited many publications in the field of ophthalmology.

His areas of expertise include degenerative macular disease such as age related macular degeneration, diabetic retinopathy, choroidal neovascularisation, inherited retinal diseases such as retinitis pigmentosa, visual electrophysiology, fundus angiography and retinal vascular disease.

In diagnostics, his expertise is identifying and evaluating retinal diseases. He receives referrals from eye and retinal specialists both locally and from the region, for expert opinion and advice on management of these complex and sometimes rare cases. In the field of visual electrophysiology, he studied under Professors Graham Holder and Geoffrey Arden and helped establish an ISCEV-standards visual electrophysiology laboratory at the Singapore National Eye Centre.

In the field of macular degeneration, he specializes in the use of verteporfin photodynamic therapy, anti-VEGF therapy and combination therapy in Asia. He also specializes in the use of laser techniques using the PASCAL system, and intravitreal adjunctive therapies such as Lucentis and Triamcinolone for the treatment of severe diabetic retinopathy, diabetic macular oedema, retinal vein obstruction and other retinal vascular diseases.