title: Reply.
authors.affiliation: Singapore National Eye Centre, Singapore Eye Research Institute, Singapore. Electronic address: donald.tan.t.h@snec.com.sg.
authors.forename: Donald
authors.initials: D
authors.lastname: Tan
authors.affiliation: Singapore National Eye Centre, Singapore Eye Research Institute, Singapore.
authors.forename: Audrey
authors.initials: A
authors.lastname: Chia