Research Discussion Paper January 2011 number 5. Matching lighting to sight loss

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1 Research Discussion Paper January 2011 number 5 Matching lighting to sight loss This publication is informed by the following research conducted on behalf of Thomas Pocklington Trust: Brodrick S and Barrett J (2008) Lighting needs of people with particular eye conditions (A scoping study which analyses existing Pocklington data). Evans BJW, Sawyerr H, Jessa Z, Brodrick S and Slater AI (2008) A pilot study of lighting and low vision in older people, published in Lighting Res. Technol. 2010; 42: There are many different forms of sight loss, and each shows a wide range of individual differences. This paper seeks to address whether or not it is possible to design forms of lighting that can be easily applied for the benefit of large numbers of people with different forms of sight loss. Evans et al. (2008) concluded that it was not, and that individual assessment of lighting needs was necessary. Brodrick et al. (2008) concluded that there were some rules of thumb that could usefully be employed when designing lighting for people with sight loss. A roundtable meeting was held to discuss this divergence of views, and it identified four general problems which would face anyone seeking to use lighting to improve the quality of life for people with different forms of sight loss. They were: Missing fundamental data Limited understanding of what is important to people with sight loss regarding lighting matters Lack of understanding of lighting technology How to ensure the most appropriate lighting. Thomas Pocklington Trust 1

2 The meeting also identified seven specific research topics deserving attention. They were: Identifying significant everyday tasks Establishing the role of lighting in ensuring people with sight loss can move safely around their home/work environment Finding the level of light exposure required for stable circadian rhythms Exploring all the consequences of light source colour for vision Examining indirect glare Determining the ease of use of different types of lighting controls Providing information on lighting for use by optometrists. Background Thomas Pocklington Trust has funded two studies looking at the possibilities for matching lighting to various forms of sight loss. One (Evans et al., 2008) was a laboratory study in which people with cataract or macular degeneration or both carried out a series of simple everyday tasks, i.e. walking down a corridor, inserting a plug into a socket, sorting pills of different sizes, and reading, at three different illuminances: 50, 200 and 800 lx. Performance on the tasks tended to improve at higher illuminances but the average results masked large individual differences, so much so that it was concluded that the best approach to providing optimal lighting for people with different forms of sight loss would be to evaluate each individual separately. The second study (Brodrick S and Barrett J, 2008) examined the data collected in three implementation projects in which an assessment team visited the homes of people with sight loss and proposed lighting modifications designed to improve the quality of life of the individual. Following the installation of the lighting modifications, residents were asked to indicate their satisfaction with the changes. It proved to be impossible to identify which lighting conditions were most suited for specific forms of sight loss. However, the authors were confident enough to identify some generally applicable rules of thumb for use when designing lighting for people with sight loss. These two studies recommend very different approaches to matching lighting to sight loss. The objective of this paper is to consider what research is needed in order to answer the question: 2 Thomas Pocklington Trust

3 Is it possible to design forms of lighting that can be easily applied for the benefit of large numbers of people with different forms of sight loss? Many of the general problems that need to be addressed were identified at a roundtable organised by Thomas Pocklington Trust and attended by vision and lighting specialists. These problems are outlined below. General problems The general problems faced by anyone seeking to use lighting to improve the quality of life for people with different forms of sight loss are of four different types. They can be characterised as: Missing fundamental data Limited understanding of what is important to people with sight loss regarding lighting matters Lack of understanding of lighting technology How to ensure the most appropriate lighting. Missing fundamental data The missing information is in the areas of demography and capability. Demographic information is required to determine how many people there are with different forms of sight loss who would benefit from different lighting treatments. It would also be desirable to have some idea of how stable this information is over time and how likely it is that more than one form of sight loss will be present in one location. It is only worth considering matching lighting to forms of sight loss when there are significant numbers of people who would benefit from different lighting treatments and where these numbers are stable over long periods. With regard to capability, different forms of sight loss impose different limits on visual function. For example, any change which produces greater light scatter in the eye, such as cataract, is likely to enhance the perception of glare. However, studies of glare have all been conducted using people with normal vision and the only advice available about limiting glare is that the light source should not be viewed directly. This may not be enough to eliminate glare for some forms of sight loss. A similar situation applies to colour discrimination and identification. Most research about the effect of lighting on the ability to discriminate between and identify colours has been done Thomas Pocklington Trust 3

4 using people with normal vision or some form of defective colour vision, but not with the more common forms of sight loss. Such information would be useful when selecting suitable light sources for people with sight loss. Understanding what matters Much research on the benefits of lighting for people with different forms of sight loss has concentrated on measuring specific visual functions. This is useful information because it is reasonable to assume that if lighting improves a visual function, for example visual acuity, the ability to perform tasks dependent on that visual function will be improved. However, in everyday life people are not interested in visual function as such. What they are concerned about is whether or not they can do the tasks that matter to them and how the room will appear to them. Identifying what these tasks are and the importance of room appearance is necessary to ensure the success of any lighting designed to enhance the quality of life of people with sight loss. Lighting technology There is a vast array of lighting technology available. This is not only a matter of light sources, luminaires and control systems, each with their own properties, but also of cost, portability and ease of use by people with sight loss. The question that needs to be addressed here is to what extent lighting technology can be packaged to provide a single lighting system that is flexible enough to be easily matched to different forms of sight loss, in situ. The development of such a lighting system would make it much easier to provide better lighting for people with sight loss. How to ensure the most appropriate lighting It is always possible to design lighting to match the needs of a single individual in a single location. All that is required is an experienced lighting designer, a lot of feedback from the user and a generous budget. The problem becomes more difficult when lighting needs to be installed for many different individuals with different forms of sight loss in separate locations, particularly if the person controlling the installation has no experience of lighting. Ease of solution will depend on the answers to some of the problems discussed above. For example, if a package of lighting equipment flexible enough to meet the task requirements of a wide range of people with different forms of sight loss could be 4 Thomas Pocklington Trust

5 developed, then delivery would be relatively simple. A lighting package could be defined and a guidance document describing how to install and adjust the lighting would be sufficient. However, if such flexible lighting was not possible, then a series of demonstration projects might be required so that a menu of alternative lighting designs could be developed and publicised. Specific research topics In addition to recognising general problems, the roundtable also identified seven specific research topics that deserve urgent attention. All the research topics fall within one or more of the general themes identified above. They are: Identify significant everyday tasks In everyday life, people with sight loss are not so much concerned with visual function but rather with the tasks they can do, those they cannot do and those they cannot do but would like to do. Identifying these tasks would help to establish what form of lighting is needed to enhance the quality of life of people with sight loss and where it has to be installed. Establish the role of lighting in safe movement Lighting enables eyesight to function and that helps with safe movement, but lighting can do more than this. Lighting equipment itself can serve as a signal to help balance and stability and can provide guidance. The value of these roles needs to be explored. Finding the level of light exposure required for stable circadian rhythms Light has an effect on human physiology beyond enabling eyesight to operate. Specifically, the alternating pattern of light and dark over a 24-hour period synchronises the human circadian system, aiding wakefulness during the day and sleep during the night. The circadian system operates at a very fundamental level of physiology so it is important to ensure that lighting designed to maximise the visual abilities of those with sight loss is enough to ensure stable operation of the circadian system. Exploring all the consequences of light source colour for vision Different light sources emit different combinations of wavelengths and hence produce light of different colours. The wavelength combinations will influence the amount of light reaching the retina Thomas Pocklington Trust 5

6 of people with sight loss and hence their visual capabilities. The colour appearance of light is also subject to strong individual preferences. Understanding all the consequences of light source colour for vision is useful in establishing the costs and benefits of different light sources. Examining indirect glare Glare from lighting is a well-known phenomenon but current systems of glare control do not reflect the sensitivities of people with sight loss. The usual advice is to avoid a direct view of the light source but it is possible for glare to occur indirectly, i.e., without a direct view of the light source. The perception of indirect glare from luminaires and even bright patches on walls and ceilings, by people with sight loss, needs to be examined. Determining the ease of use of different types of lighting control There are a number of different controls used for switching and dimming lighting, from simple switches through rotary dimmers to touch dimmers. These controls differ in their ease of use by people with sight loss. Determining the suitability of different types of lighting controls for use by people with sight loss would enable the design of lighting systems better matched to their capabilities. Providing information on lighting for use by optometrists Optometrists are often asked for advice about lighting by and for people with sight loss. There is a need to provide such advice in a form accessible to optometrists, particularly with regard to suitable replacements for the incandescent light bulbs that are widely used in homes but are now being withdrawn from the market. Author Dr Peter Boyce Professor Emeritus Rensselaer Polytechnic Institute Troy, New York, USA 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 How to obtain further information RNIB and Thomas Pocklington Trust (2009) Make the most of your sight. Improve the lighting in your home. Brodrick S and Barrett J (2008) Lighting needs of people with particular eye conditions (A scoping study which analyses existing Pocklington data). Evans BJW, Sawyerr H, Jessa Z, Brodrick S and Slater AI (2008) A pilot study of lighting and low vision in older people, published in Lighting Res. Technol. 2010; 42, Evans BJW, Sawyerr H, Jessa Z, Brodrick S Research Findings number 31 A pilot study of lighting and low vision in older people, published by Thomas Pocklington Trust March 2010 For more detail on the research projects discussed above, contact Thomas Pocklington Trust 5 Castle Row, Horticultural Place, London W4 4JQ Tel: info@pocklington-trust.org.uk Web: Copies of this report in large print, audiotape or CD, Braille and electronic format are available from Thomas Pocklington Trust 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. 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