“The first step in quality lighting design for seniors is to understand the effects of aging on the human eye.”
The importance of effective lighting becomes even more critical as our population ages. As we age, physiological changes in the eye result in a reduction in the quality of life and a decrease in safety due to falls. The first step in quality lighting design for seniors is to understand the effects of aging on the human eye.
As the eye ages, the following changes result:
- Less light is transmitted to the retina. Studies published by the Illuminating Engineering Society of North America indicate that only 25% of the light reaches the retina at age 75 than it did at age 25.
- The eye becomes more susceptible to glare. Glare results in both a decrease in ability to understand what is in the field of view as well as actual physical discomfort.
- The visual field of view yellows.
- The eye becomes less able to adapt to significant changes in light levels typically found at entries into buildings.
- The ability for the eye to detect contrast decreases, resulting in a blurring of the field of view. This situation can actually worsen as the light level in a space increases because light scatters across the retina as the eye ages, a phenomenon called preretinal scatter.
Before comprehensive studies were completed, the solution to lighting senior environments was to simply increase the light levels to offset the reduction in light transmission to the retina. However, quantity does not equate to quality and overlighting can actually worsen the environment. Strategic planning of lighting layouts is required.
When lighting spaces for seniors, some simple ground rules should be followed:
- Use indirect lighting whenever possible, allowing for higher light levels without excessive glare. Standard downlights and recessed fluorescent troffers can cause significant glare problems.
- Avoid traditional cold white or warm white fluorescent lamps. Use high color rendering, tri-phosphor lamps with electronic ballasts.
- Avoid low hanging decorative light fixtures with exposed lamps. Cover the exposed lamps with shades to avoid glare.
- Use higher artificial light levels in entry vestibules in order to gradually transition from the exterior to the interior of a building, hence reducing the drastic changes in light levels typical in these locations.
- Use contrasting finishes to define important changes in the environment. For example, the shade and color contrast between walls and floors are extremely important in reducing falls. Make sure that the risers and treads in stairwells are well contrasted.
- Avoid highly polished or glass tables, which can further increase discomfort glare.
- In residential environments, light all showers and use kitchen undercabinet lighting.
Although advances are constantly being made in understanding vision problems, we are still faced with the effects of age on the human eye. The good news is by understanding these effects, we can design lighting systems that compensate for these changes and improve the quality of life.
– John D. Reese, PE, LEED AP
John is a Licensed Electrical Engineer, Lighting Designer, LEED Accredited Professional, and Managing Principal of Reese Engineering. Please feel free to contact John for further details regarding the above information.