Most people who are considered legally blind have some residual vision and can perceive some level of light. Low vision can be the result of a myriad of conditions, many of these associated with aging. The strong correlation of low vision and aging, coupled with the trend of an exponential growth in the 60 plus age group, highlights the importance of providing environments with well designed lighting.
An inadequate or inconsistent level of general or ambient lighting to a space can present a formidable problem to many people with low vision. People with low or affected vision often require two to three times the amount of light to perform tasks and to facilitate general orientation and mobility.
Providing general lighting to an appropriate level is therefore essential. Lux levels for rooms of a variety of functions are outlined in Australian Standards AS1680 Interior lighting, and more specifically for people with low vision in AS1428.2 Design for access and mobility Part 2: Enhanced and additional requirements – Buildings and facilities.
The lighting levels indicated in these can sometimes become problematic for designers when attempting to also meet sustainability requirements for buildings given the amount of energy used. Even though these standards provide important guidance in designing lighting, a number of considerations can be incorporated to assist in improving the function and safety of an internal space.
Location of lighting
Wall washers which use the walls and ceilings as reflectors, assist in illuminating without glare as well as defining a space more effectively. It can assist with identifying rooms and therefore facilitate orientation.
Daylight is generally a source of light that most people (including people with low vision) find very useful. Maximizing this through the use of windows and openings, while also considering their location and potential for providing a glare source is essential. Providing a means of excluding low-elevation sunlight such as an eave, screen or blind will assist in reducing glare.
Consideration of anticipated occupant sightlines within a space is essential in the provision of both natural and artificial light sources in order to reduce direct glare and any associated silhouetting.
Locating light switches to the latch side of a door and aligning them with the height of door hardware also provides consistency for users in locating them upon entering a potentially dark space.
Use of task focused lighting
Providing focused illumination for particular activities in set locations improves visual clarity and can offset fatigue. Task lighting enhances contrast and improves clarity and should be provided in areas where people are expected to perform specific tasks such as reading, writing, craftwork, preparing food etc. Task lighting should always be provided in conjunction with general lighting.
Selection of appropriate lighting and fittings
Quality fluorescent light sources provide a more diffuse source of light which reduces the possibility of dark areas and provides a more consistent lighting level. Triphosporus halogens should be selected as they provide more natural lighting. Where incandescent or halogen lighting is preferred, it should be noted that these produce a narrower band of light. A larger number of lighting fittings will therefore be required to provide uniform lighting across a space and to reduce the production of shadows which can also be disorienting for people with low vision.
Diffusers should generally be used to reduce glare, and light fittings should not be mounted at or around eye level. Up-lighting projecting into habitable spaces (especially along established paths of travel) should also be avoided.
Use of finishes
Providing contrasting finishes between items such as walls and floors, as well as furniture and fitment items, assists in defining a space and a safe path through the building. Attention should also be given to the reflectivity of finishes. Matte finishes are preferred to reduce potential glare from reflected light sources.
Ensuring a logical design and layout is provided within a room based on the activities performed in the space will assist people with low vision to anticipate and search out appropriate routes for navigation.
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