A pilot study of lighting and low vision in older people

Transcription

1 Research findings March 2010 number 31 A pilot study of lighting and low vision in older people This publication summarises findings from research which was commissioned and funded by Thomas Pocklington Trust and carried out at the Institute of Optometry by Bruce Evans, Hannah Sawyerr, Zahra Jessa and Steve Brodrick. The research investigated the influence of lighting on performance of activities of daily living in 24 older people with low vision caused by cataract and/or macular degeneration. The research found that: Subjects tended to perform better under brighter conditions, but the average results masked large individual variations. It was demonstrated that lighting had a big effect on most participants performance in at least one task, but the optimal lighting level varied idiosyncratically from one subject to another. It is concluded that the best approach to providing optimal lighting for older people with low vision might be to assess their preference and performance individually at different lighting levels. Thomas Pocklington Trust 1

2 Introduction Visual impairment is common in older people and major causes include cataract and age-related macular degeneration (AMD). Previous research suggests that people with AMD benefit from increased light levels but this may not be the case with cataract, which causes light scatter inside the eye. The purpose of this pilot study was to investigate the influence of lighting on performance of activities of daily living in older people with these conditions. Activities of daily living Four activities of daily living were used in the research, all of which are likely to be encountered in everyday life: 1. Walking along a corridor with an uneven floor 2. Inserting an electrical plug in a socket 3. Sorting pills 4. Reading All the tasks were scored for speed and accuracy, although with tasks 1-3 errors were so rare that analysis of these was not appropriate. The scoring system for the rate of reading task took account of errors. Participants were asked to state their subjective preferences, indicating which of the three lighting levels (see below) they found best and which worst for each task. In addition, for the rate of reading task, the lighting level was adjusted to determine the level that each participant found best for clarity and then for comfort. Procedure Participants were people over the age of 65 years who had cataract (LOCS III grades 2, 3, or 4) and/or AMD (Harvard system grades 2, 3, or 4). The participants were placed in three groups: cataract only (11 subjects), AMD only (6 subjects), and cataract combined with AMD (7 subjects). Each task was carried out under three lighting levels: 50 lux (dim), 200 lux (medium), and 800 lux (bright). 2 Thomas Pocklington Trust

3 Results In the corridor walking task, the cataract group performed significantly better under bright rather than dim lighting. In the plug in socket task, the AMD group performed significantly better under the bright lighting rather than the medium or dim lighting. In the pill sorting task, the cataract group performed significantly better under the medium rather than the dim or bright lighting. In the reading task, the cataract group performed significantly better under the bright rather than the dim lighting. The possibility that idiosyncratic effects of lighting outweigh any general effects of disease condition was investigated by identifying participants whose performance in any task under one of the lighting conditions was more than 20% better than the performance under one of the other conditions. These idiosyncratic effects were common, affecting all participants in the AMD group, all but one in the combined group, and seven out of eleven in the cataract group. These idiosyncratic effects were not all in the direction indicated by the group means. It is thought unlikely that these large idiosyncratic effects reflect errors in the data. Although the subjective preferences also showed individual variations, the preferred and non-preferred lighting level only agreed with the lighting level that gave best and worst performance in 37% of cases. The pill-sorting and reading tasks were felt to yield the most useful and relevant data. It is noted that recruitment is challenging in this age group: many people declined to participate because they were already making many visits to clinics for healthcare investigations and treatments. Thomas Pocklington Trust 3

4 Conclusions The results of this pilot study should be interpreted with caution in view of the modest sample sizes. The individual data show that although participants tended to perform better under bright lighting, there were some in every task and every group who performed best under dim lighting and in most tasks and groups there were some participants who performed best under medium lighting. It is suggested that it is more valuable to test the effect of lighting for each individual person rather than to make any general assumptions about whether increasing or decreasing lighting levels is likely to be helpful simply by considering a person s visual status or disease condition alone. The results do not support the concept of one lighting level fits all, but rather indicate that older people with reduced vision should be encouraged to participate in determining the lighting level that they find is best for them. In terms of the provision of suitable housing, it might be ideal to have a test room where the lighting level can be varied in order to find the optimal setting for an individual. It may be useful to gather both objective data (e.g. rate of reading) and subjective data (expressed preference) to help find this optimal setting. A useful approach for further research would be to carry out repeated measures of a task, such as the rate of reading. In addition, the type of lighting and directional nature of lighting would be interesting areas for future research. 4 Thomas Pocklington Trust

5 Author Professor Bruce Evans Institute of Optometry Newington Causeway London SE1 6DS How to obtain further information A more detailed description of this research can be found in the following paper by Evans and colleagues; Bruce Evans, H Sawyerr, Z Jessa, S Brodrick, and A I Slater. A pilot study of lighting and low vision in older people. Lighting Research and Technology, first published on July 22, 2009 as doi: / Copies of this report in large print, audio tape or CD, Braille and electronic format are available from: Thomas Pocklington Trust 5 Castle Row Horticultural Place London W4 4JQ Telephone: info@pocklington-trust.org.uk Web: Thomas Pocklington Trust 5

6 Background on Pocklington Thomas Pocklington Trust is a leading provider of housing, care and support services for people with sight loss in the UK. Each year we also fund a programme of social and public health research and development projects. Pocklington s operations offer a range of sheltered and supported housing, residential care, respite care, day services, resource centres and volunteer-based community support services. We strive to improve continuously the quality standards in our operational centres to meet the changing needs and expectations of our current and future service users. We are proud to be an Investor in People and a Positive about Disability organisation. Our research and development programme aims to identify practical ways to improve the lives of people with sight loss by improving social inclusion, independence and quality of life, and improving and developing service outcomes as well as focusing on public health issues. In this publication, the terms visually impaired people, blind and partially sighted people and people with sight loss all refer to people who are blind or who have partial sight. 6 Thomas Pocklington Trust

7 Notes Thomas Pocklington Trust 7

8 5 Castle Row Horticultural Place Chiswick London W4 4JQ Tel: Web: Published by Thomas Pocklington Trust Registered Charity No Company Registered No ISBN