Designing to Accommodate the Aging Eye

Color Perception

The perception of color is a second element of change as the eye ages.  Typically, the eye loses sensitivity in the blue portion of the spectrum over time.  This is caused by a yellowing of the membrane that sheathes the retina on the back of the eye.  If we think of the optical structure of the eye as very complex organic plastics, we may then visualize the yellowing as the same process as is seen in the plastic lenses of light fixtures that are exposed to ultraviolet light.

Design Options

For the designer, the loss in blue sensitivity poses several problems.  It is possible to increase the blue spectral component through the selection of light sources; or, the color palette may be chosen to provide increased reflectance in the blue hues.  The difficulty arises when the space must also accommodate the “normal” young eye and not present a distorted view of the space.  The solution is the careful selection of the color palette for the space with careful attention to metamerism, a color shift due to a change in light source.  The second element is the use of high color-rendering light sources like quartz-halogen lamps and tri-phosphor fluorescent and LED lamps which come in a variety of color temperatures from warm to very cool.  Each of these sources offer greater energy efficiency and lamp life over standard incandescent lamps.

The Visual Environment

In the space itself, edges and transitions must be clearly delineated.  This may be accomplished though the selection of contrasting colors, textures and reflectances.  The placement of the light sources is also important; glare and veiling luminances must be avoided.  An improperly placed light source can increase the illumination and energy required to perform a task.  Properly placed, the light sources lead the occupants through a space and provide the visual cues for safe passage and task accomplishment.

The proper placement of visual stimuli and their illumination are essential to the creation of the visual environment.  These include artwork, display items and accessories that are placed throughout the space in conjunction with accent lighting.  While much of the resident’s time may be spent reading, sewing of performing close-in tasks, visual health requires the eye to relax every few minutes; this is accomplished by providing many objects in the visual field upon which to focus.

Visual Task Considerations

Because a multitude of visual tasks are performed in the space, multiple light sources and controls must be provided to allow flexibility for the resident to vary the visual environment.  These may include switches, dimmers, remote controls and occupancy sensors.  Occupancy sensors can turn on the illumination before the occupant reaches a hazardous location and saves energy by extinguishing the lighting when no one is present.  Diffuse and indirect light sources are useful for general illumination; however, direct or point sources may be desirable when structure, contrast or shadowing are important.

Daylighting

Daylight is another consideration in the design of spaces.  There are two key considerations.  First, the color palette of the space must be compatible with the introduction of daylight in addition to it coordination with the electric lighting.  The use of tinted glass can also complicate the design trade-offs.  Second, illumination requirements are greater during daylight hours because the eye has adapted to the higher ambient light levels.  This dictates that more illumination is required in the rear or darker portions of the space during the day and that general illumination levels may be reduced as nighttime approaches.  Care must be taken in the selection of window treatments to ensure that they control the daylight so that tasks can be comfortably performed.

Conclusions

As the eye ages, changes take place that reduce visual performance.  By paying careful attention to the selection of light sources and the design of the visual environment, occupants can perform their daily routine comfortably and productively.

About the Authors

With over thirty years of experience in Lighting and Interior Design, Moira Quinn Leite is the President and Design Principal of M. Quinn Designs Incorporated.  The firm has offices in Edina, Minnesota, and Annandale, Virginia.  She is a member of the Illuminating Engineering Society of North America, the International Furnishings and Design Association, and Allied Member of the American Society of Interior Designers.

Michael Leite is a Registered Professional Engineer with Luminous Environments, Incorporated.  His experience includes indoor and outdoor lighting, low-level photometry, and marine lighting.  His papers have been published by the CIE, IESNA, American Society of Naval Engineers, and the American Society of Civil Engineers.  He holds a patent for optical waveguide technology and was the editor for the Recommended Practice for Marine Lighting published by the IESNA.

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