title: Authors' response.
authors.affiliation: Department of Ophthalmology, St Bernard's Hospital, Gibraltar, UK.
authors.forename: Philip G
authors.initials: PG
authors.lastname: Griffiths
authors.affiliation: Department of Ophthalmology, York Teaching Hospital Foundation Trust, York, UK.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Taylor
authors.affiliation: University of York, York, UK.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Henderson
authors.affiliation: School of Optometry & Vision Science, University of Bradford, Bradford, UK.
authors.forename: Brendan T
authors.initials: BT
authors.lastname: Barrett