Elderly People Require Three Times As Much Light As Young People For Visual Clarity

As the visual system ages, the range of distances over which focus can be achieved is diminished, the amount of light reaching the retina is reduced, more of the light entering the eye is scattered, and the color of the light is altered by preferential absorption of short wavelengths.

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.

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.

Everyone who lives long enough will experience these changes, but with increasing age there is also an increased probability of pathological change in the eye. These pathological changes can lead to partial sight and, ultimately, blindness. The consequences of all these changes in the visual system with age are reduced visual acuity, reduced contrast sensitivity, reduced color discrimination, increased time taken to adapt to light and sudden changes in luminance and increased sensitivity to glare. 

Lighting can be used to compensate for these changes, to some extent, and hence can be used to support the independence and quality of life of the elderly. 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

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.

Enhance the 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.

Improve Color Sensitivity

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 will 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.