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The prevalence of visual impairment in the UK A review of the literature

Rosemary Tate, Liam Smeeth, Jennifer Evans, Astrid Fletcher Dept of Epidemiology & Population Health London School of Hygiene & Tropical Medicine Chris Owen St George’s Hospital Medical School Alicja Rudnicka Wolfson Institute of Preventive Medicine

Report commissioned by the Royal National Institute for the Blind

Acknowledgements Funding for the review was provided by the Royal National Institute for the Blind Advisory Committee Liz Bates (Director Corporate Policy, Ashton, Leigh & Wigan Primary Care Trust) Prof Ian Bruce (VOLPROF, City University) Prof Alistair Fielder (Professor of Ophthalmology, Imperial College London and Western Eye Hospital) Dr Carol Lupton (Policy Research Programme, Department of Health Dr Angela McCullagh (Research Director, The Pocklington Trust) RNIB Lesley-Anne Alexander (Chief Executive) Nigel Charles (Research Development Manager) Fazilet Hadi (Director of Policy) Dr Adam Ockelford (Assistant Director, Education and Employment) Many thanks also to Sue Keil at RNIB who provided extra information for Chapter 5. Special thanks to Nigel Charles for commissioning this project and for invaluable support and advice. Authors’ details Rosemary Tate PhD, research fellow, London School of Hygiene & Tropical Medicine (now at Institute of Child Health) Liam Smeeth MRCP, Senior clinical lecturer in epidemiology, London School of Hygiene & Tropical Medicine Jennifer Evans PhD, lecturer in epidemiology, London School of Hygiene & Tropical Medicine Astrid Fletcher PhD, Professor of epidemiology, London School of Hygiene & Tropical Medicine Chris Owen PhD, Senior Research Fellow in Epidemiology, St George's Hospital Medical School Alicja Rudnicka PhD, Lecturer in Epidemiology & Medical Statistics, Wolfson Institute of Preventive Medicine Contribution of authors Rosemary Tate undertook the literature review and preparation of main tables. Liam Smeeth reviewed and updated Chapter 5 on Children. Jenny Evans contributed the section on blindness registrations and provided critical comments on the review. Chris Owen and Alicja Rudnicka carried out the analyses and wrote the material for Chapter 6. Astrid Fletcher took overall responsibility for the project and wrote the Summary, Chapter 1 and Chapter 7. Authors’ potential conflict of interest Data on self reported visual difficulties and visual acuity measures reviewed in this report comes from the MRC funded Trial of assessment and management of older people in the community (Principal Investigator Astrid Fletcher), the associated causes of vision impairment study funded by the The Pocklington Trust (with Jenny Evans and Richard Wormald) and the nested MRC funded trial of screening for vision impairment within the main MRC Trial (with Liam Smeeth). 1

Summary We identified three approaches to describing visual problems in the population. 1. Visual difficulties - based on self-report of difficulties with vision related functions ranging from single item questions to disability scales. Most studies have used questions on difficulty in “reading newsprint” as minimum criteria for difficulties with seeing. 2. Clinical measures, predominantly visual acuity. Distance visual acuity is the basis for categorising vision impairment in the WHO International Classification of Diseases (ICD). Most studies have measured distance acuity using an illuminated Snellen chart. Visual acuity can be measured with usual aids if worn i.e. contact lenses or glasses (“presenting vision”) or after full refraction for refractive error (“best corrected visual acuity”). In surveys full refraction may not be available and studies may use pinhole correction to try to remove some of the refractive error (pinhole corrected visual acuity). Results may be presented as binocular vision or as vision in the better eye. The WHO ICD classifications use best corrected visual acuity ie vision in the better eye after full correction. Vision impairment is defined as a Snellen acuity