How does the human visual system change, as one grows older? What can be done to make lighting more effective for the aging eye? Here are some lighting principles that can help specifiers, builders, facility managers, and homeowners light interior spaces.
Contributed by Mariana Figueiro, PhD, Lighting Research Center, Rensselaer Polytechnic Institute

As visual capabilities decrease with age, the ability to focus at different distances gets more noticeable — particularly after age 45. This is called presbyopia. As one grows older, less light reaches the back of the eyes because the pupil gets smaller and the crystalline lens inside the eye becomes thicker, absorbing more light. A 60-year old receives about 1/3 of as much light at the retina as a 20-year old.

The Principles:
More light on task - Older adults need at least 50% more light than younger adults on reading tasks. As much as 10 times more light will be required to see fine details (e.g., reading small points) or low-contrast objects (e.g., black thread on blue cloth). Rather than increasing overall light levels, increase light levels in areas where visual tasks are performed by placing adjustable light fixtures close to the task, or by selecting light bulbs with more lumens (look for lumen rating on the package, not wattage; be careful not to exceed the lamp fixture wattage).
Fluorescent light bulbs are usually a good option because they provide more lumens per watt than incandescent light bulbs, they last 10 times longer than common incandescent light bulbs; they are available with excellent color, plenty of light, no buzz or flicker; they are cooler to touch and, they can be dimmed.
Increase ambient light levels by keeping surface finishes light in color. Light-colored walls, floors, and ceilings will help minimize shadows and increase overall light levels in the living environment. Place light fixtures where visibility is important, such as below kitchen countertop, over kitchen sink, in the shower, closet and laundry spaces.
Less glare - Although more light on the task is required for the older eye to see, care should be taken to avoid glare. Glare is experienced when light sources or bright reflections in the field of view impair vision, or are simply uncomfortable. Hide the light source with a shade, baffles, non-shiny louvers, or a shielding board. Use frosted light bulbs where seeing the light bulb is unavoidable (e.g., fan lights) and avoid clear glass light fixtures. Minimize shiny floor finishes and polished surfaces to reduce reflection of the light bulb.
Balanced light levels - Due to optical, and perhaps neural changes to the eye, older adults cannot completely adapt to dim lighting conditions, so illuminance levels in transitional spaces, such as hallways and entrance foyers should be similar to those of the adjacent spaces. Use balanced ambient light levels in adjacent spaces. Choose multiple switches or dimmers to create intermediate light levels in transitional spaces that lead from bright, outdoor areas, to dim, indoor spaces. Transitional spaces should be dimmer at night and brighter during the day.
Color enhancement - Color discrimination is poorer for older adults because of scattered light in the eye. The aged lens also absorbs relatively more blue light, so it is particularly difficult to discriminate between, say, dark purples and maroons. Use light bulbs with high lumens and good color rendering properties. Choose light bulbs with color rendering indices (CRI) of 80 or greater.
o More contrast - Because contrast sensitivity is reduced with age, the visibility of important objects, such as stair edges, curbs, ramps, or doorways, can be greatly improved by increasing their contrast with paint or similar techniques. Use contrasting contrast colors to mark edges, such as doorframes, baseboards, steps, and sharp edges.

How to make lighting more effective for the aging circadian system
The impact of low light levels on the circadian system and sleep may be further compounded by age-related neurological changes in the circadian system. Moreover, older adults often lead more sedentary lives, less likely to leave indoor living environments which limits their access to daylight.
Lighting can also be used to consolidate sleep patterns. Although there is still some debate about the exact lighting characteristics affecting the circadian system, it is known that relatively higher light levels are needed to activate the circadian system compared to the visual system. For reading, the daytime (photopic) visual response is maximally sensitive to light at 555 nm (yellow-green light), while the circadian system is a “blue-sky detector,” maximally sensitive to wavelengths shorter than 470 nm. Timing and duration of light exposure are important for the circadian system.

But, remember, lighting is only one element of the interior design. Select appropriate surface finishes and enhance relevant information, such as sharp edges, architectural transitions, and doorways so that the visual environment is not cluttered. Lighting techniques associated with appropriate interior finishes will help older adults maintain their independence and stay home longer.



Look for the ENERGY STAR label on the box of light bulbs and lighting fixtures