1. Academic Unit for Ageing & Stroke Research , Bradford Institute for Health Research, , Duckworth Lane, Bradford, West Yorkshire BD9 6RJ , UK
2. Bradford Teaching Hospitals NHS Foundation Trust , Bradford Institute for Health Research, , Duckworth Lane, Bradford, West Yorkshire BD9 6RJ , UK
3. Leeds Institute of Health Sciences, University of Leeds , Leeds , UK
4. Academic Unit of Ophthalmology, Institute of Inflammation & Ageing, College of Medical and Dental Sciences, University of Birmingham , Birmingham , UK