Why Lighting is Important for the Aging EyeWednesday 18 June 2014
Lighting can make a critical difference to elderly people with deteriorating vision. Engineers, architects and designers trying to design spaces that can be fully utilized by both old and young must consider how to meet the visual needs of the increasingly large elderly population. The challenge is to create a visual environment to compensate for the most typical kinds of vision loss by enhancing remaining vision with lighting and clever use of contrast.
More Light Is Required Less light reaches the retina in an aging eye than it does in a younger eye. First, pupil size reduces with age so less light enters the eye. Second, the lens, which is normally clear in a young person, yellows and thickens with age, also impeding the transmission of light. The result is that a 60-year-old receives only about 40% of the same amount of available light as a 20-year-old. An older person, therefore, may see poorly under dim conditions, and lose both acuity and contrast sensitivity.
It is also difficult for an aging visual system to adapt quickly to dramatic changes in brightness. Even within a single space, it may be hard to see darker areas if other surfaces are much brighter. A general, or "ambient," light should therefore assure that there are no dark areas in a space. The space should also be bright enough to allow for good visibility so people can move around. In addition, light needs to be available for tasks requiring the ability to see and distinguish detail. The finer the detail of the task, such as counting money at a cashier's counter, cooking on the stove or reading, the more light is needed.
Glare Reduction Is Important The solution may appear simple: Just provide more light overall, and extra light in task areas. However, many older people become increasingly sensitive to glare, and higher levels of light can be uncomfortable, even disabling. Typically, older people experience glare because their lenses thicken and develop cloudy patches, so light is absorbed and scattered across the retina, making the image less clear. Glare is felt most acutely when a bright object is seen against a dark background, such as headlights at night. A bright light source, such as a bulb or lamp that is well shielded from view, may provide good lighting in a room and minimize the chances for glare. Examples include indirect lighting located in architectural features such as soffit and lighting fixtures or coves; and fixtures, or "luminaires," which have shielding features such as baffles or louvers. Highly reflectant surfaces such as white walls and ceilings maximize and balance the light in space, washing out severe shadows.
Contrast Because contrast sensitivity often declines with age, enhancing the contrast on relevant objects allows a person to recognize and distinguish edges. A stair tread with a contrasting-color stripe, for instance, may provide a measure of safety for someone who may not see the edge of the stair. Bold signs with a contrasting color background are easier to read.
Color Since many elderly lose some color sensitivity, good color-rendering lamps may enhance the color discrimination that remains. Incandescent lamps, including halogen, render colors very well. Many types of fluorescent lamps render colors nearly as well as incandescent lamps, and have much longer lives.
Environments where seeing is easy and comfortable help to promote an elderly person's sense of competence and independence, and add to quality of life. Furthermore, when improving lighting to meet the visual needs of the elderly, everyone's visual environment is likely to improve.
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