1. Ophthalmology Department, Addenbrooke's Teaching Hospital, Hills Road, Cambridge CB2 0QQ, UK
2. Ophthalmology Department, Blackpool Fylde and Wyre Hospitals, Whinney Heys Road, Blackpool FY3 8NR, UK
3. Neurology Department, Blackpool Fylde and Wyre Hospitals, Whinney Heys Road, Blackpool FY3 8NR, UK
4. Ophthalmology Department, Barnsley General Hospital, Gawber Road, Barnsley S75 2EP, UK