1 Department of Neurology (TU), National Neuroscience Institute, Singapore; Department of Ophthalmology (KZL, CFC, TKY, RA), NHG Eye Institute, Tan Tock Seng Hospital, Singapore; Department of General Medicine (KV, PHU), Tan Tock Seng Hospital, Singapore; National Centre for Infectious Diseases (GSET), Tan Tock Seng Hospital, Singapore ; Singapore Eye Research Institute (RA), Singapore; and Lee Kong Chian School of Medicine (RA), Nanyang Technological University, Singapore.