title: Authors' reply.
authors.affiliation: Division of Optometry and Visual Science, City, University of London, London, UK.
authors.forename: John G
authors.initials: JG
authors.lastname: Lawrenson
authors.affiliation: UCL Institute of Ophthalmology, London, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Baker
authors.affiliation: Corneo-Plastic Unit, Queen Victoria Hospital, East Grinstead, UK.
authors.forename: Gokulan
authors.initials: G
authors.lastname: Ratnarajan
authors.affiliation: Manchester Academic Health Sciences Centre, Manchester Royal Eye Hospital, Manchester, UK.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Harper
authors.affiliation: Division of Optometry and Visual Science, City, University of London, London, UK.
authors.forename: David F
authors.initials: DF
authors.lastname: Edgar