Joanna M Jefferis1, Alan J Connor2, Michael P Clarke3. 1. Department of Ophthalmology, Royal Hallamshire Hospital, Sheffield, UK jojefferis@doctors.org.uk. 2. Department of Ophthalmology, Hospital for Sick Children, Toronto, Canada Newcastle Eye Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Royal Victoria Infirmary, Newcastle Upon Tyne NE1 4LP, UK. 3. Newcastle Eye Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Royal Victoria Infirmary, Newcastle Upon Tyne NE1 4LP, UK.